diff --git a/go/vendor/google.golang.org/genproto/LICENSE b/go/vendor/google.golang.org/genproto/LICENSE
new file mode 100644
index 0000000..d645695
--- /dev/null
+++ b/go/vendor/google.golang.org/genproto/LICENSE
@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
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+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
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+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
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+      Licensor for the purpose of discussing and improving the Work, but
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+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
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+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
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+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
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+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
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+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
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+      Work (including but not limited to damages for loss of goodwill,
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+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
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+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
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+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
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+
+   Copyright [yyyy] [name of copyright owner]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
diff --git a/go/vendor/google.golang.org/genproto/googleapis/rpc/status/status.pb.go b/go/vendor/google.golang.org/genproto/googleapis/rpc/status/status.pb.go
new file mode 100644
index 0000000..d13bcba
--- /dev/null
+++ b/go/vendor/google.golang.org/genproto/googleapis/rpc/status/status.pb.go
@@ -0,0 +1,159 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: google/rpc/status.proto
+
+package status
+
+import (
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	any "github.com/golang/protobuf/ptypes/any"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+// The `Status` type defines a logical error model that is suitable for different
+// programming environments, including REST APIs and RPC APIs. It is used by
+// [gRPC](https://github.com/grpc). The error model is designed to be:
+//
+// - Simple to use and understand for most users
+// - Flexible enough to meet unexpected needs
+//
+// # Overview
+//
+// The `Status` message contains three pieces of data: error code, error message,
+// and error details. The error code should be an enum value of
+// [google.rpc.Code][google.rpc.Code], but it may accept additional error codes if needed.  The
+// error message should be a developer-facing English message that helps
+// developers *understand* and *resolve* the error. If a localized user-facing
+// error message is needed, put the localized message in the error details or
+// localize it in the client. The optional error details may contain arbitrary
+// information about the error. There is a predefined set of error detail types
+// in the package `google.rpc` that can be used for common error conditions.
+//
+// # Language mapping
+//
+// The `Status` message is the logical representation of the error model, but it
+// is not necessarily the actual wire format. When the `Status` message is
+// exposed in different client libraries and different wire protocols, it can be
+// mapped differently. For example, it will likely be mapped to some exceptions
+// in Java, but more likely mapped to some error codes in C.
+//
+// # Other uses
+//
+// The error model and the `Status` message can be used in a variety of
+// environments, either with or without APIs, to provide a
+// consistent developer experience across different environments.
+//
+// Example uses of this error model include:
+//
+// - Partial errors. If a service needs to return partial errors to the client,
+//     it may embed the `Status` in the normal response to indicate the partial
+//     errors.
+//
+// - Workflow errors. A typical workflow has multiple steps. Each step may
+//     have a `Status` message for error reporting.
+//
+// - Batch operations. If a client uses batch request and batch response, the
+//     `Status` message should be used directly inside batch response, one for
+//     each error sub-response.
+//
+// - Asynchronous operations. If an API call embeds asynchronous operation
+//     results in its response, the status of those operations should be
+//     represented directly using the `Status` message.
+//
+// - Logging. If some API errors are stored in logs, the message `Status` could
+//     be used directly after any stripping needed for security/privacy reasons.
+type Status struct {
+	// The status code, which should be an enum value of [google.rpc.Code][google.rpc.Code].
+	Code int32 `protobuf:"varint,1,opt,name=code,proto3" json:"code,omitempty"`
+	// A developer-facing error message, which should be in English. Any
+	// user-facing error message should be localized and sent in the
+	// [google.rpc.Status.details][google.rpc.Status.details] field, or localized by the client.
+	Message string `protobuf:"bytes,2,opt,name=message,proto3" json:"message,omitempty"`
+	// A list of messages that carry the error details.  There is a common set of
+	// message types for APIs to use.
+	Details              []*any.Any `protobuf:"bytes,3,rep,name=details,proto3" json:"details,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}   `json:"-"`
+	XXX_unrecognized     []byte     `json:"-"`
+	XXX_sizecache        int32      `json:"-"`
+}
+
+func (m *Status) Reset()         { *m = Status{} }
+func (m *Status) String() string { return proto.CompactTextString(m) }
+func (*Status) ProtoMessage()    {}
+func (*Status) Descriptor() ([]byte, []int) {
+	return fileDescriptor_24d244abaf643bfe, []int{0}
+}
+
+func (m *Status) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Status.Unmarshal(m, b)
+}
+func (m *Status) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Status.Marshal(b, m, deterministic)
+}
+func (m *Status) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Status.Merge(m, src)
+}
+func (m *Status) XXX_Size() int {
+	return xxx_messageInfo_Status.Size(m)
+}
+func (m *Status) XXX_DiscardUnknown() {
+	xxx_messageInfo_Status.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Status proto.InternalMessageInfo
+
+func (m *Status) GetCode() int32 {
+	if m != nil {
+		return m.Code
+	}
+	return 0
+}
+
+func (m *Status) GetMessage() string {
+	if m != nil {
+		return m.Message
+	}
+	return ""
+}
+
+func (m *Status) GetDetails() []*any.Any {
+	if m != nil {
+		return m.Details
+	}
+	return nil
+}
+
+func init() {
+	proto.RegisterType((*Status)(nil), "google.rpc.Status")
+}
+
+func init() { proto.RegisterFile("google/rpc/status.proto", fileDescriptor_24d244abaf643bfe) }
+
+var fileDescriptor_24d244abaf643bfe = []byte{
+	// 209 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0x12, 0x4f, 0xcf, 0xcf, 0x4f,
+	0xcf, 0x49, 0xd5, 0x2f, 0x2a, 0x48, 0xd6, 0x2f, 0x2e, 0x49, 0x2c, 0x29, 0x2d, 0xd6, 0x2b, 0x28,
+	0xca, 0x2f, 0xc9, 0x17, 0xe2, 0x82, 0x48, 0xe8, 0x15, 0x15, 0x24, 0x4b, 0x49, 0x42, 0x15, 0x81,
+	0x65, 0x92, 0x4a, 0xd3, 0xf4, 0x13, 0xf3, 0x2a, 0x21, 0xca, 0x94, 0xd2, 0xb8, 0xd8, 0x82, 0xc1,
+	0xda, 0x84, 0x84, 0xb8, 0x58, 0x92, 0xf3, 0x53, 0x52, 0x25, 0x18, 0x15, 0x18, 0x35, 0x58, 0x83,
+	0xc0, 0x6c, 0x21, 0x09, 0x2e, 0xf6, 0xdc, 0xd4, 0xe2, 0xe2, 0xc4, 0xf4, 0x54, 0x09, 0x26, 0x05,
+	0x46, 0x0d, 0xce, 0x20, 0x18, 0x57, 0x48, 0x8f, 0x8b, 0x3d, 0x25, 0xb5, 0x24, 0x31, 0x33, 0xa7,
+	0x58, 0x82, 0x59, 0x81, 0x59, 0x83, 0xdb, 0x48, 0x44, 0x0f, 0x6a, 0x21, 0xcc, 0x12, 0x3d, 0xc7,
+	0xbc, 0xca, 0x20, 0x98, 0x22, 0xa7, 0x38, 0x2e, 0xbe, 0xe4, 0xfc, 0x5c, 0x3d, 0x84, 0xa3, 0x9c,
+	0xb8, 0x21, 0xf6, 0x06, 0x80, 0x94, 0x07, 0x30, 0x46, 0x99, 0x43, 0xa5, 0xd2, 0xf3, 0x73, 0x12,
+	0xf3, 0xd2, 0xf5, 0xf2, 0x8b, 0xd2, 0xf5, 0xd3, 0x53, 0xf3, 0xc0, 0x86, 0xe9, 0x43, 0xa4, 0x12,
+	0x0b, 0x32, 0x8b, 0x91, 0xfc, 0x69, 0x0d, 0xa1, 0x16, 0x31, 0x31, 0x07, 0x05, 0x38, 0x27, 0xb1,
+	0x81, 0x55, 0x1a, 0x03, 0x02, 0x00, 0x00, 0xff, 0xff, 0xa4, 0x53, 0xf0, 0x7c, 0x10, 0x01, 0x00,
+	0x00,
+}
diff --git a/go/vendor/google.golang.org/grpc/.travis.yml b/go/vendor/google.golang.org/grpc/.travis.yml
new file mode 100644
index 0000000..a775585
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/.travis.yml
@@ -0,0 +1,39 @@
+language: go
+
+matrix:
+  include:
+  - go: 1.11.x
+    env: VET=1 GO111MODULE=on
+  - go: 1.11.x
+    env: RACE=1 GO111MODULE=on
+  - go: 1.11.x
+    env: RUN386=1
+  - go: 1.11.x
+    env: GRPC_GO_RETRY=on
+  - go: 1.10.x
+  - go: 1.9.x
+  - go: 1.9.x
+    env: GAE=1
+  - go: 1.8.x
+  - go: 1.6.x
+
+go_import_path: google.golang.org/grpc
+
+before_install:
+  - if [[ "${GO111MODULE}" = "on" ]]; then mkdir "${HOME}/go"; export GOPATH="${HOME}/go"; fi
+  - if [[ -n "${RUN386}" ]]; then export GOARCH=386; fi
+  - if [[ "${TRAVIS_EVENT_TYPE}" = "cron" && -z "${RUN386}" ]]; then RACE=1; fi
+  - if [[ "${TRAVIS_EVENT_TYPE}" != "cron" ]]; then VET_SKIP_PROTO=1; fi
+
+install:
+  - try3() { eval "$*" || eval "$*" || eval "$*"; }
+  - try3 'if [[ "${GO111MODULE}" = "on" ]]; then go mod download; else make testdeps; fi'
+  - if [[ "${GAE}" = 1 ]]; then source ./install_gae.sh; make testappenginedeps; fi
+  - if [[ "${VET}" = 1 ]]; then ./vet.sh -install; fi
+
+script:
+  - set -e
+  - if [[ "${VET}" = 1 ]]; then ./vet.sh; fi
+  - if [[ "${GAE}" = 1 ]]; then make testappengine; exit 0; fi
+  - if [[ "${RACE}" = 1 ]]; then make testrace; exit 0; fi
+  - make test
diff --git a/go/vendor/google.golang.org/grpc/AUTHORS b/go/vendor/google.golang.org/grpc/AUTHORS
new file mode 100644
index 0000000..e491a9e
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/AUTHORS
@@ -0,0 +1 @@
+Google Inc.
diff --git a/go/vendor/google.golang.org/grpc/CONTRIBUTING.md b/go/vendor/google.golang.org/grpc/CONTRIBUTING.md
new file mode 100644
index 0000000..0863eb2
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/CONTRIBUTING.md
@@ -0,0 +1,36 @@
+# How to contribute
+
+We definitely welcome your patches and contributions to gRPC!
+
+If you are new to github, please start by reading [Pull Request howto](https://help.github.com/articles/about-pull-requests/)
+
+## Legal requirements
+
+In order to protect both you and ourselves, you will need to sign the
+[Contributor License Agreement](https://identity.linuxfoundation.org/projects/cncf).
+
+## Guidelines for Pull Requests
+How to get your contributions merged smoothly and quickly.
+ 
+- Create **small PRs** that are narrowly focused on **addressing a single concern**. We often times receive PRs that are trying to fix several things at a time, but only one fix is considered acceptable, nothing gets merged and both author's & review's time is wasted. Create more PRs to address different concerns and everyone will be happy.
+ 
+- For speculative changes, consider opening an issue and discussing it first. If you are suggesting a behavioral or API change, consider starting with a [gRFC proposal](https://github.com/grpc/proposal). 
+ 
+- Provide a good **PR description** as a record of **what** change is being made and **why** it was made. Link to a github issue if it exists.
+ 
+- Don't fix code style and formatting unless you are already changing that line to address an issue. PRs with irrelevant changes won't be merged. If you do want to fix formatting or style, do that in a separate PR.
+ 
+- Unless your PR is trivial, you should expect there will be reviewer comments that you'll need to address before merging. We expect you to be reasonably responsive to those comments, otherwise the PR will be closed after 2-3 weeks of inactivity.
+ 
+- Maintain **clean commit history** and use **meaningful commit messages**. PRs with messy commit history are difficult to review and won't be merged. Use `rebase -i upstream/master` to curate your commit history and/or to bring in latest changes from master (but avoid rebasing in the middle of a code review).
+ 
+- Keep your PR up to date with upstream/master (if there are merge conflicts, we can't really merge your change).
+ 
+- **All tests need to be passing** before your change can be merged. We recommend you **run tests locally** before creating your PR to catch breakages early on.
+  - `make all` to test everything, OR
+  - `make vet` to catch vet errors
+  - `make test` to run the tests
+  - `make testrace` to run tests in race mode
+
+- Exceptions to the rules can be made if there's a compelling reason for doing so.
+ 
diff --git a/go/vendor/google.golang.org/grpc/LICENSE b/go/vendor/google.golang.org/grpc/LICENSE
new file mode 100644
index 0000000..d645695
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/LICENSE
@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
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+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
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+      meet the following conditions:
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+          Derivative Works a copy of this License; and
+
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+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
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+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
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+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
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+          that such additional attribution notices cannot be construed
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+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright [yyyy] [name of copyright owner]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
diff --git a/go/vendor/google.golang.org/grpc/Makefile b/go/vendor/google.golang.org/grpc/Makefile
new file mode 100644
index 0000000..41a754f
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/Makefile
@@ -0,0 +1,60 @@
+all: vet test testrace testappengine
+
+build: deps
+	go build google.golang.org/grpc/...
+
+clean:
+	go clean -i google.golang.org/grpc/...
+
+deps:
+	go get -d -v google.golang.org/grpc/...
+
+proto:
+	@ if ! which protoc > /dev/null; then \
+		echo "error: protoc not installed" >&2; \
+		exit 1; \
+	fi
+	go generate google.golang.org/grpc/...
+
+test: testdeps
+	go test -cpu 1,4 -timeout 7m google.golang.org/grpc/...
+
+testappengine: testappenginedeps
+	goapp test -cpu 1,4 -timeout 7m google.golang.org/grpc/...
+
+testappenginedeps:
+	goapp get -d -v -t -tags 'appengine appenginevm' google.golang.org/grpc/...
+
+testdeps:
+	go get -d -v -t google.golang.org/grpc/...
+
+testrace: testdeps
+	go test -race -cpu 1,4 -timeout 7m google.golang.org/grpc/...
+
+updatedeps:
+	go get -d -v -u -f google.golang.org/grpc/...
+
+updatetestdeps:
+	go get -d -v -t -u -f google.golang.org/grpc/...
+
+vet: vetdeps
+	./vet.sh
+
+vetdeps:
+	./vet.sh -install
+
+.PHONY: \
+	all \
+	build \
+	clean \
+	deps \
+	proto \
+	test \
+	testappengine \
+	testappenginedeps \
+	testdeps \
+	testrace \
+	updatedeps \
+	updatetestdeps \
+	vet \
+	vetdeps
diff --git a/go/vendor/google.golang.org/grpc/README.md b/go/vendor/google.golang.org/grpc/README.md
new file mode 100644
index 0000000..29ffb00
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/README.md
@@ -0,0 +1,67 @@
+# gRPC-Go
+
+[![Build Status](https://travis-ci.org/grpc/grpc-go.svg)](https://travis-ci.org/grpc/grpc-go) [![GoDoc](https://godoc.org/google.golang.org/grpc?status.svg)](https://godoc.org/google.golang.org/grpc) [![GoReportCard](https://goreportcard.com/badge/grpc/grpc-go)](https://goreportcard.com/report/github.com/grpc/grpc-go)
+
+The Go implementation of [gRPC](https://grpc.io/): A high performance, open source, general RPC framework that puts mobile and HTTP/2 first. For more information see the [gRPC Quick Start: Go](https://grpc.io/docs/quickstart/go.html) guide.
+
+Installation
+------------
+
+To install this package, you need to install Go and setup your Go workspace on your computer. The simplest way to install the library is to run:
+
+```
+$ go get -u google.golang.org/grpc
+```
+
+Prerequisites
+-------------
+
+This requires Go 1.6 or later. Go 1.7 will be required soon.
+
+Constraints
+-----------
+The grpc package should only depend on standard Go packages and a small number of exceptions. If your contribution introduces new dependencies which are NOT in the [list](http://godoc.org/google.golang.org/grpc?imports), you need a discussion with gRPC-Go authors and consultants.
+
+Documentation
+-------------
+See [API documentation](https://godoc.org/google.golang.org/grpc) for package and API descriptions and find examples in the [examples directory](examples/).
+
+Performance
+-----------
+See the current benchmarks for some of the languages supported in [this dashboard](https://performance-dot-grpc-testing.appspot.com/explore?dashboard=5652536396611584&widget=490377658&container=1286539696).
+
+Status
+------
+General Availability [Google Cloud Platform Launch Stages](https://cloud.google.com/terms/launch-stages).
+
+FAQ
+---
+
+#### Compiling error, undefined: grpc.SupportPackageIsVersion
+
+Please update proto package, gRPC package and rebuild the proto files:
+ - `go get -u github.com/golang/protobuf/{proto,protoc-gen-go}`
+ - `go get -u google.golang.org/grpc`
+ - `protoc --go_out=plugins=grpc:. *.proto`
+
+#### How to turn on logging
+
+The default logger is controlled by the environment variables. Turn everything
+on by setting:
+
+```
+GRPC_GO_LOG_VERBOSITY_LEVEL=99 GRPC_GO_LOG_SEVERITY_LEVEL=info
+```
+
+#### The RPC failed with error `"code = Unavailable desc = transport is closing"`
+
+This error means the connection the RPC is using was closed, and there are many
+possible reasons, including:
+ 1. mis-configured transport credentials, connection failed on handshaking
+ 1. bytes disrupted, possibly by a proxy in between
+ 1. server shutdown
+
+It can be tricky to debug this because the error happens on the client side but
+the root cause of the connection being closed is on the server side. Turn on
+logging on __both client and server__, and see if there are any transport
+errors.
diff --git a/go/vendor/google.golang.org/grpc/backoff.go b/go/vendor/google.golang.org/grpc/backoff.go
new file mode 100644
index 0000000..fa31565
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/backoff.go
@@ -0,0 +1,38 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// See internal/backoff package for the backoff implementation. This file is
+// kept for the exported types and API backward compatility.
+
+package grpc
+
+import (
+	"time"
+)
+
+// DefaultBackoffConfig uses values specified for backoff in
+// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
+var DefaultBackoffConfig = BackoffConfig{
+	MaxDelay: 120 * time.Second,
+}
+
+// BackoffConfig defines the parameters for the default gRPC backoff strategy.
+type BackoffConfig struct {
+	// MaxDelay is the upper bound of backoff delay.
+	MaxDelay time.Duration
+}
diff --git a/go/vendor/google.golang.org/grpc/balancer.go b/go/vendor/google.golang.org/grpc/balancer.go
new file mode 100644
index 0000000..5aeb646
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/balancer.go
@@ -0,0 +1,391 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"net"
+	"sync"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/naming"
+	"google.golang.org/grpc/status"
+)
+
+// Address represents a server the client connects to.
+//
+// Deprecated: please use package balancer.
+type Address struct {
+	// Addr is the server address on which a connection will be established.
+	Addr string
+	// Metadata is the information associated with Addr, which may be used
+	// to make load balancing decision.
+	Metadata interface{}
+}
+
+// BalancerConfig specifies the configurations for Balancer.
+//
+// Deprecated: please use package balancer.
+type BalancerConfig struct {
+	// DialCreds is the transport credential the Balancer implementation can
+	// use to dial to a remote load balancer server. The Balancer implementations
+	// can ignore this if it does not need to talk to another party securely.
+	DialCreds credentials.TransportCredentials
+	// Dialer is the custom dialer the Balancer implementation can use to dial
+	// to a remote load balancer server. The Balancer implementations
+	// can ignore this if it doesn't need to talk to remote balancer.
+	Dialer func(context.Context, string) (net.Conn, error)
+}
+
+// BalancerGetOptions configures a Get call.
+//
+// Deprecated: please use package balancer.
+type BalancerGetOptions struct {
+	// BlockingWait specifies whether Get should block when there is no
+	// connected address.
+	BlockingWait bool
+}
+
+// Balancer chooses network addresses for RPCs.
+//
+// Deprecated: please use package balancer.
+type Balancer interface {
+	// Start does the initialization work to bootstrap a Balancer. For example,
+	// this function may start the name resolution and watch the updates. It will
+	// be called when dialing.
+	Start(target string, config BalancerConfig) error
+	// Up informs the Balancer that gRPC has a connection to the server at
+	// addr. It returns down which is called once the connection to addr gets
+	// lost or closed.
+	// TODO: It is not clear how to construct and take advantage of the meaningful error
+	// parameter for down. Need realistic demands to guide.
+	Up(addr Address) (down func(error))
+	// Get gets the address of a server for the RPC corresponding to ctx.
+	// i) If it returns a connected address, gRPC internals issues the RPC on the
+	// connection to this address;
+	// ii) If it returns an address on which the connection is under construction
+	// (initiated by Notify(...)) but not connected, gRPC internals
+	//  * fails RPC if the RPC is fail-fast and connection is in the TransientFailure or
+	//  Shutdown state;
+	//  or
+	//  * issues RPC on the connection otherwise.
+	// iii) If it returns an address on which the connection does not exist, gRPC
+	// internals treats it as an error and will fail the corresponding RPC.
+	//
+	// Therefore, the following is the recommended rule when writing a custom Balancer.
+	// If opts.BlockingWait is true, it should return a connected address or
+	// block if there is no connected address. It should respect the timeout or
+	// cancellation of ctx when blocking. If opts.BlockingWait is false (for fail-fast
+	// RPCs), it should return an address it has notified via Notify(...) immediately
+	// instead of blocking.
+	//
+	// The function returns put which is called once the rpc has completed or failed.
+	// put can collect and report RPC stats to a remote load balancer.
+	//
+	// This function should only return the errors Balancer cannot recover by itself.
+	// gRPC internals will fail the RPC if an error is returned.
+	Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error)
+	// Notify returns a channel that is used by gRPC internals to watch the addresses
+	// gRPC needs to connect. The addresses might be from a name resolver or remote
+	// load balancer. gRPC internals will compare it with the existing connected
+	// addresses. If the address Balancer notified is not in the existing connected
+	// addresses, gRPC starts to connect the address. If an address in the existing
+	// connected addresses is not in the notification list, the corresponding connection
+	// is shutdown gracefully. Otherwise, there are no operations to take. Note that
+	// the Address slice must be the full list of the Addresses which should be connected.
+	// It is NOT delta.
+	Notify() <-chan []Address
+	// Close shuts down the balancer.
+	Close() error
+}
+
+// RoundRobin returns a Balancer that selects addresses round-robin. It uses r to watch
+// the name resolution updates and updates the addresses available correspondingly.
+//
+// Deprecated: please use package balancer/roundrobin.
+func RoundRobin(r naming.Resolver) Balancer {
+	return &roundRobin{r: r}
+}
+
+type addrInfo struct {
+	addr      Address
+	connected bool
+}
+
+type roundRobin struct {
+	r      naming.Resolver
+	w      naming.Watcher
+	addrs  []*addrInfo // all the addresses the client should potentially connect
+	mu     sync.Mutex
+	addrCh chan []Address // the channel to notify gRPC internals the list of addresses the client should connect to.
+	next   int            // index of the next address to return for Get()
+	waitCh chan struct{}  // the channel to block when there is no connected address available
+	done   bool           // The Balancer is closed.
+}
+
+func (rr *roundRobin) watchAddrUpdates() error {
+	updates, err := rr.w.Next()
+	if err != nil {
+		grpclog.Warningf("grpc: the naming watcher stops working due to %v.", err)
+		return err
+	}
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	for _, update := range updates {
+		addr := Address{
+			Addr:     update.Addr,
+			Metadata: update.Metadata,
+		}
+		switch update.Op {
+		case naming.Add:
+			var exist bool
+			for _, v := range rr.addrs {
+				if addr == v.addr {
+					exist = true
+					grpclog.Infoln("grpc: The name resolver wanted to add an existing address: ", addr)
+					break
+				}
+			}
+			if exist {
+				continue
+			}
+			rr.addrs = append(rr.addrs, &addrInfo{addr: addr})
+		case naming.Delete:
+			for i, v := range rr.addrs {
+				if addr == v.addr {
+					copy(rr.addrs[i:], rr.addrs[i+1:])
+					rr.addrs = rr.addrs[:len(rr.addrs)-1]
+					break
+				}
+			}
+		default:
+			grpclog.Errorln("Unknown update.Op ", update.Op)
+		}
+	}
+	// Make a copy of rr.addrs and write it onto rr.addrCh so that gRPC internals gets notified.
+	open := make([]Address, len(rr.addrs))
+	for i, v := range rr.addrs {
+		open[i] = v.addr
+	}
+	if rr.done {
+		return ErrClientConnClosing
+	}
+	select {
+	case <-rr.addrCh:
+	default:
+	}
+	rr.addrCh <- open
+	return nil
+}
+
+func (rr *roundRobin) Start(target string, config BalancerConfig) error {
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	if rr.done {
+		return ErrClientConnClosing
+	}
+	if rr.r == nil {
+		// If there is no name resolver installed, it is not needed to
+		// do name resolution. In this case, target is added into rr.addrs
+		// as the only address available and rr.addrCh stays nil.
+		rr.addrs = append(rr.addrs, &addrInfo{addr: Address{Addr: target}})
+		return nil
+	}
+	w, err := rr.r.Resolve(target)
+	if err != nil {
+		return err
+	}
+	rr.w = w
+	rr.addrCh = make(chan []Address, 1)
+	go func() {
+		for {
+			if err := rr.watchAddrUpdates(); err != nil {
+				return
+			}
+		}
+	}()
+	return nil
+}
+
+// Up sets the connected state of addr and sends notification if there are pending
+// Get() calls.
+func (rr *roundRobin) Up(addr Address) func(error) {
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	var cnt int
+	for _, a := range rr.addrs {
+		if a.addr == addr {
+			if a.connected {
+				return nil
+			}
+			a.connected = true
+		}
+		if a.connected {
+			cnt++
+		}
+	}
+	// addr is only one which is connected. Notify the Get() callers who are blocking.
+	if cnt == 1 && rr.waitCh != nil {
+		close(rr.waitCh)
+		rr.waitCh = nil
+	}
+	return func(err error) {
+		rr.down(addr, err)
+	}
+}
+
+// down unsets the connected state of addr.
+func (rr *roundRobin) down(addr Address, err error) {
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	for _, a := range rr.addrs {
+		if addr == a.addr {
+			a.connected = false
+			break
+		}
+	}
+}
+
+// Get returns the next addr in the rotation.
+func (rr *roundRobin) Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error) {
+	var ch chan struct{}
+	rr.mu.Lock()
+	if rr.done {
+		rr.mu.Unlock()
+		err = ErrClientConnClosing
+		return
+	}
+
+	if len(rr.addrs) > 0 {
+		if rr.next >= len(rr.addrs) {
+			rr.next = 0
+		}
+		next := rr.next
+		for {
+			a := rr.addrs[next]
+			next = (next + 1) % len(rr.addrs)
+			if a.connected {
+				addr = a.addr
+				rr.next = next
+				rr.mu.Unlock()
+				return
+			}
+			if next == rr.next {
+				// Has iterated all the possible address but none is connected.
+				break
+			}
+		}
+	}
+	if !opts.BlockingWait {
+		if len(rr.addrs) == 0 {
+			rr.mu.Unlock()
+			err = status.Errorf(codes.Unavailable, "there is no address available")
+			return
+		}
+		// Returns the next addr on rr.addrs for failfast RPCs.
+		addr = rr.addrs[rr.next].addr
+		rr.next++
+		rr.mu.Unlock()
+		return
+	}
+	// Wait on rr.waitCh for non-failfast RPCs.
+	if rr.waitCh == nil {
+		ch = make(chan struct{})
+		rr.waitCh = ch
+	} else {
+		ch = rr.waitCh
+	}
+	rr.mu.Unlock()
+	for {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+			return
+		case <-ch:
+			rr.mu.Lock()
+			if rr.done {
+				rr.mu.Unlock()
+				err = ErrClientConnClosing
+				return
+			}
+
+			if len(rr.addrs) > 0 {
+				if rr.next >= len(rr.addrs) {
+					rr.next = 0
+				}
+				next := rr.next
+				for {
+					a := rr.addrs[next]
+					next = (next + 1) % len(rr.addrs)
+					if a.connected {
+						addr = a.addr
+						rr.next = next
+						rr.mu.Unlock()
+						return
+					}
+					if next == rr.next {
+						// Has iterated all the possible address but none is connected.
+						break
+					}
+				}
+			}
+			// The newly added addr got removed by Down() again.
+			if rr.waitCh == nil {
+				ch = make(chan struct{})
+				rr.waitCh = ch
+			} else {
+				ch = rr.waitCh
+			}
+			rr.mu.Unlock()
+		}
+	}
+}
+
+func (rr *roundRobin) Notify() <-chan []Address {
+	return rr.addrCh
+}
+
+func (rr *roundRobin) Close() error {
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	if rr.done {
+		return errBalancerClosed
+	}
+	rr.done = true
+	if rr.w != nil {
+		rr.w.Close()
+	}
+	if rr.waitCh != nil {
+		close(rr.waitCh)
+		rr.waitCh = nil
+	}
+	if rr.addrCh != nil {
+		close(rr.addrCh)
+	}
+	return nil
+}
+
+// pickFirst is used to test multi-addresses in one addrConn in which all addresses share the same addrConn.
+// It is a wrapper around roundRobin balancer. The logic of all methods works fine because balancer.Get()
+// returns the only address Up by resetTransport().
+type pickFirst struct {
+	*roundRobin
+}
diff --git a/go/vendor/google.golang.org/grpc/balancer/balancer.go b/go/vendor/google.golang.org/grpc/balancer/balancer.go
new file mode 100644
index 0000000..ee1703f
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/balancer/balancer.go
@@ -0,0 +1,287 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package balancer defines APIs for load balancing in gRPC.
+// All APIs in this package are experimental.
+package balancer
+
+import (
+	"errors"
+	"net"
+	"strings"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/resolver"
+)
+
+var (
+	// m is a map from name to balancer builder.
+	m = make(map[string]Builder)
+)
+
+// Register registers the balancer builder to the balancer map. b.Name
+// (lowercased) will be used as the name registered with this builder.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple Balancers are
+// registered with the same name, the one registered last will take effect.
+func Register(b Builder) {
+	m[strings.ToLower(b.Name())] = b
+}
+
+// Get returns the resolver builder registered with the given name.
+// Note that the compare is done in a case-insenstive fashion.
+// If no builder is register with the name, nil will be returned.
+func Get(name string) Builder {
+	if b, ok := m[strings.ToLower(name)]; ok {
+		return b
+	}
+	return nil
+}
+
+// SubConn represents a gRPC sub connection.
+// Each sub connection contains a list of addresses. gRPC will
+// try to connect to them (in sequence), and stop trying the
+// remainder once one connection is successful.
+//
+// The reconnect backoff will be applied on the list, not a single address.
+// For example, try_on_all_addresses -> backoff -> try_on_all_addresses.
+//
+// All SubConns start in IDLE, and will not try to connect. To trigger
+// the connecting, Balancers must call Connect.
+// When the connection encounters an error, it will reconnect immediately.
+// When the connection becomes IDLE, it will not reconnect unless Connect is
+// called.
+//
+// This interface is to be implemented by gRPC. Users should not need a
+// brand new implementation of this interface. For the situations like
+// testing, the new implementation should embed this interface. This allows
+// gRPC to add new methods to this interface.
+type SubConn interface {
+	// UpdateAddresses updates the addresses used in this SubConn.
+	// gRPC checks if currently-connected address is still in the new list.
+	// If it's in the list, the connection will be kept.
+	// If it's not in the list, the connection will gracefully closed, and
+	// a new connection will be created.
+	//
+	// This will trigger a state transition for the SubConn.
+	UpdateAddresses([]resolver.Address)
+	// Connect starts the connecting for this SubConn.
+	Connect()
+}
+
+// NewSubConnOptions contains options to create new SubConn.
+type NewSubConnOptions struct {
+	// CredsBundle is the credentials bundle that will be used in the created
+	// SubConn. If it's nil, the original creds from grpc DialOptions will be
+	// used.
+	CredsBundle credentials.Bundle
+}
+
+// ClientConn represents a gRPC ClientConn.
+//
+// This interface is to be implemented by gRPC. Users should not need a
+// brand new implementation of this interface. For the situations like
+// testing, the new implementation should embed this interface. This allows
+// gRPC to add new methods to this interface.
+type ClientConn interface {
+	// NewSubConn is called by balancer to create a new SubConn.
+	// It doesn't block and wait for the connections to be established.
+	// Behaviors of the SubConn can be controlled by options.
+	NewSubConn([]resolver.Address, NewSubConnOptions) (SubConn, error)
+	// RemoveSubConn removes the SubConn from ClientConn.
+	// The SubConn will be shutdown.
+	RemoveSubConn(SubConn)
+
+	// UpdateBalancerState is called by balancer to nofity gRPC that some internal
+	// state in balancer has changed.
+	//
+	// gRPC will update the connectivity state of the ClientConn, and will call pick
+	// on the new picker to pick new SubConn.
+	UpdateBalancerState(s connectivity.State, p Picker)
+
+	// ResolveNow is called by balancer to notify gRPC to do a name resolving.
+	ResolveNow(resolver.ResolveNowOption)
+
+	// Target returns the dial target for this ClientConn.
+	Target() string
+}
+
+// BuildOptions contains additional information for Build.
+type BuildOptions struct {
+	// DialCreds is the transport credential the Balancer implementation can
+	// use to dial to a remote load balancer server. The Balancer implementations
+	// can ignore this if it does not need to talk to another party securely.
+	DialCreds credentials.TransportCredentials
+	// CredsBundle is the credentials bundle that the Balancer can use.
+	CredsBundle credentials.Bundle
+	// Dialer is the custom dialer the Balancer implementation can use to dial
+	// to a remote load balancer server. The Balancer implementations
+	// can ignore this if it doesn't need to talk to remote balancer.
+	Dialer func(context.Context, string) (net.Conn, error)
+	// ChannelzParentID is the entity parent's channelz unique identification number.
+	ChannelzParentID int64
+}
+
+// Builder creates a balancer.
+type Builder interface {
+	// Build creates a new balancer with the ClientConn.
+	Build(cc ClientConn, opts BuildOptions) Balancer
+	// Name returns the name of balancers built by this builder.
+	// It will be used to pick balancers (for example in service config).
+	Name() string
+}
+
+// PickOptions contains addition information for the Pick operation.
+type PickOptions struct {
+	// FullMethodName is the method name that NewClientStream() is called
+	// with. The canonical format is /service/Method.
+	FullMethodName string
+	// Header contains the metadata from the RPC's client header.  The metadata
+	// should not be modified; make a copy first if needed.
+	Header metadata.MD
+}
+
+// DoneInfo contains additional information for done.
+type DoneInfo struct {
+	// Err is the rpc error the RPC finished with. It could be nil.
+	Err error
+	// Trailer contains the metadata from the RPC's trailer, if present.
+	Trailer metadata.MD
+	// BytesSent indicates if any bytes have been sent to the server.
+	BytesSent bool
+	// BytesReceived indicates if any byte has been received from the server.
+	BytesReceived bool
+}
+
+var (
+	// ErrNoSubConnAvailable indicates no SubConn is available for pick().
+	// gRPC will block the RPC until a new picker is available via UpdateBalancerState().
+	ErrNoSubConnAvailable = errors.New("no SubConn is available")
+	// ErrTransientFailure indicates all SubConns are in TransientFailure.
+	// WaitForReady RPCs will block, non-WaitForReady RPCs will fail.
+	ErrTransientFailure = errors.New("all SubConns are in TransientFailure")
+)
+
+// Picker is used by gRPC to pick a SubConn to send an RPC.
+// Balancer is expected to generate a new picker from its snapshot every time its
+// internal state has changed.
+//
+// The pickers used by gRPC can be updated by ClientConn.UpdateBalancerState().
+type Picker interface {
+	// Pick returns the SubConn to be used to send the RPC.
+	// The returned SubConn must be one returned by NewSubConn().
+	//
+	// This functions is expected to return:
+	// - a SubConn that is known to be READY;
+	// - ErrNoSubConnAvailable if no SubConn is available, but progress is being
+	//   made (for example, some SubConn is in CONNECTING mode);
+	// - other errors if no active connecting is happening (for example, all SubConn
+	//   are in TRANSIENT_FAILURE mode).
+	//
+	// If a SubConn is returned:
+	// - If it is READY, gRPC will send the RPC on it;
+	// - If it is not ready, or becomes not ready after it's returned, gRPC will block
+	//   until UpdateBalancerState() is called and will call pick on the new picker.
+	//
+	// If the returned error is not nil:
+	// - If the error is ErrNoSubConnAvailable, gRPC will block until UpdateBalancerState()
+	// - If the error is ErrTransientFailure:
+	//   - If the RPC is wait-for-ready, gRPC will block until UpdateBalancerState()
+	//     is called to pick again;
+	//   - Otherwise, RPC will fail with unavailable error.
+	// - Else (error is other non-nil error):
+	//   - The RPC will fail with unavailable error.
+	//
+	// The returned done() function will be called once the rpc has finished, with the
+	// final status of that RPC.
+	// done may be nil if balancer doesn't care about the RPC status.
+	Pick(ctx context.Context, opts PickOptions) (conn SubConn, done func(DoneInfo), err error)
+}
+
+// Balancer takes input from gRPC, manages SubConns, and collects and aggregates
+// the connectivity states.
+//
+// It also generates and updates the Picker used by gRPC to pick SubConns for RPCs.
+//
+// HandleSubConnectionStateChange, HandleResolvedAddrs and Close are guaranteed
+// to be called synchronously from the same goroutine.
+// There's no guarantee on picker.Pick, it may be called anytime.
+type Balancer interface {
+	// HandleSubConnStateChange is called by gRPC when the connectivity state
+	// of sc has changed.
+	// Balancer is expected to aggregate all the state of SubConn and report
+	// that back to gRPC.
+	// Balancer should also generate and update Pickers when its internal state has
+	// been changed by the new state.
+	HandleSubConnStateChange(sc SubConn, state connectivity.State)
+	// HandleResolvedAddrs is called by gRPC to send updated resolved addresses to
+	// balancers.
+	// Balancer can create new SubConn or remove SubConn with the addresses.
+	// An empty address slice and a non-nil error will be passed if the resolver returns
+	// non-nil error to gRPC.
+	HandleResolvedAddrs([]resolver.Address, error)
+	// Close closes the balancer. The balancer is not required to call
+	// ClientConn.RemoveSubConn for its existing SubConns.
+	Close()
+}
+
+// ConnectivityStateEvaluator takes the connectivity states of multiple SubConns
+// and returns one aggregated connectivity state.
+//
+// It's not thread safe.
+type ConnectivityStateEvaluator struct {
+	numReady            uint64 // Number of addrConns in ready state.
+	numConnecting       uint64 // Number of addrConns in connecting state.
+	numTransientFailure uint64 // Number of addrConns in transientFailure.
+}
+
+// RecordTransition records state change happening in subConn and based on that
+// it evaluates what aggregated state should be.
+//
+//  - If at least one SubConn in Ready, the aggregated state is Ready;
+//  - Else if at least one SubConn in Connecting, the aggregated state is Connecting;
+//  - Else the aggregated state is TransientFailure.
+//
+// Idle and Shutdown are not considered.
+func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState connectivity.State) connectivity.State {
+	// Update counters.
+	for idx, state := range []connectivity.State{oldState, newState} {
+		updateVal := 2*uint64(idx) - 1 // -1 for oldState and +1 for new.
+		switch state {
+		case connectivity.Ready:
+			cse.numReady += updateVal
+		case connectivity.Connecting:
+			cse.numConnecting += updateVal
+		case connectivity.TransientFailure:
+			cse.numTransientFailure += updateVal
+		}
+	}
+
+	// Evaluate.
+	if cse.numReady > 0 {
+		return connectivity.Ready
+	}
+	if cse.numConnecting > 0 {
+		return connectivity.Connecting
+	}
+	return connectivity.TransientFailure
+}
diff --git a/go/vendor/google.golang.org/grpc/balancer/base/balancer.go b/go/vendor/google.golang.org/grpc/balancer/base/balancer.go
new file mode 100644
index 0000000..23d1351
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/balancer/base/balancer.go
@@ -0,0 +1,208 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package base
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+)
+
+type baseBuilder struct {
+	name          string
+	pickerBuilder PickerBuilder
+}
+
+func (bb *baseBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
+	return &baseBalancer{
+		cc:            cc,
+		pickerBuilder: bb.pickerBuilder,
+
+		subConns: make(map[resolver.Address]balancer.SubConn),
+		scStates: make(map[balancer.SubConn]connectivity.State),
+		csEvltr:  &connectivityStateEvaluator{},
+		// Initialize picker to a picker that always return
+		// ErrNoSubConnAvailable, because when state of a SubConn changes, we
+		// may call UpdateBalancerState with this picker.
+		picker: NewErrPicker(balancer.ErrNoSubConnAvailable),
+	}
+}
+
+func (bb *baseBuilder) Name() string {
+	return bb.name
+}
+
+type baseBalancer struct {
+	cc            balancer.ClientConn
+	pickerBuilder PickerBuilder
+
+	csEvltr *connectivityStateEvaluator
+	state   connectivity.State
+
+	subConns map[resolver.Address]balancer.SubConn
+	scStates map[balancer.SubConn]connectivity.State
+	picker   balancer.Picker
+}
+
+func (b *baseBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
+	if err != nil {
+		grpclog.Infof("base.baseBalancer: HandleResolvedAddrs called with error %v", err)
+		return
+	}
+	grpclog.Infoln("base.baseBalancer: got new resolved addresses: ", addrs)
+	// addrsSet is the set converted from addrs, it's used for quick lookup of an address.
+	addrsSet := make(map[resolver.Address]struct{})
+	for _, a := range addrs {
+		addrsSet[a] = struct{}{}
+		if _, ok := b.subConns[a]; !ok {
+			// a is a new address (not existing in b.subConns).
+			sc, err := b.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{})
+			if err != nil {
+				grpclog.Warningf("base.baseBalancer: failed to create new SubConn: %v", err)
+				continue
+			}
+			b.subConns[a] = sc
+			b.scStates[sc] = connectivity.Idle
+			sc.Connect()
+		}
+	}
+	for a, sc := range b.subConns {
+		// a was removed by resolver.
+		if _, ok := addrsSet[a]; !ok {
+			b.cc.RemoveSubConn(sc)
+			delete(b.subConns, a)
+			// Keep the state of this sc in b.scStates until sc's state becomes Shutdown.
+			// The entry will be deleted in HandleSubConnStateChange.
+		}
+	}
+}
+
+// regeneratePicker takes a snapshot of the balancer, and generates a picker
+// from it. The picker is
+//  - errPicker with ErrTransientFailure if the balancer is in TransientFailure,
+//  - built by the pickerBuilder with all READY SubConns otherwise.
+func (b *baseBalancer) regeneratePicker() {
+	if b.state == connectivity.TransientFailure {
+		b.picker = NewErrPicker(balancer.ErrTransientFailure)
+		return
+	}
+	readySCs := make(map[resolver.Address]balancer.SubConn)
+
+	// Filter out all ready SCs from full subConn map.
+	for addr, sc := range b.subConns {
+		if st, ok := b.scStates[sc]; ok && st == connectivity.Ready {
+			readySCs[addr] = sc
+		}
+	}
+	b.picker = b.pickerBuilder.Build(readySCs)
+}
+
+func (b *baseBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+	grpclog.Infof("base.baseBalancer: handle SubConn state change: %p, %v", sc, s)
+	oldS, ok := b.scStates[sc]
+	if !ok {
+		grpclog.Infof("base.baseBalancer: got state changes for an unknown SubConn: %p, %v", sc, s)
+		return
+	}
+	b.scStates[sc] = s
+	switch s {
+	case connectivity.Idle:
+		sc.Connect()
+	case connectivity.Shutdown:
+		// When an address was removed by resolver, b called RemoveSubConn but
+		// kept the sc's state in scStates. Remove state for this sc here.
+		delete(b.scStates, sc)
+	}
+
+	oldAggrState := b.state
+	b.state = b.csEvltr.recordTransition(oldS, s)
+
+	// Regenerate picker when one of the following happens:
+	//  - this sc became ready from not-ready
+	//  - this sc became not-ready from ready
+	//  - the aggregated state of balancer became TransientFailure from non-TransientFailure
+	//  - the aggregated state of balancer became non-TransientFailure from TransientFailure
+	if (s == connectivity.Ready) != (oldS == connectivity.Ready) ||
+		(b.state == connectivity.TransientFailure) != (oldAggrState == connectivity.TransientFailure) {
+		b.regeneratePicker()
+	}
+
+	b.cc.UpdateBalancerState(b.state, b.picker)
+}
+
+// Close is a nop because base balancer doesn't have internal state to clean up,
+// and it doesn't need to call RemoveSubConn for the SubConns.
+func (b *baseBalancer) Close() {
+}
+
+// NewErrPicker returns a picker that always returns err on Pick().
+func NewErrPicker(err error) balancer.Picker {
+	return &errPicker{err: err}
+}
+
+type errPicker struct {
+	err error // Pick() always returns this err.
+}
+
+func (p *errPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	return nil, nil, p.err
+}
+
+// connectivityStateEvaluator gets updated by addrConns when their
+// states transition, based on which it evaluates the state of
+// ClientConn.
+type connectivityStateEvaluator struct {
+	numReady            uint64 // Number of addrConns in ready state.
+	numConnecting       uint64 // Number of addrConns in connecting state.
+	numTransientFailure uint64 // Number of addrConns in transientFailure.
+}
+
+// recordTransition records state change happening in every subConn and based on
+// that it evaluates what aggregated state should be.
+// It can only transition between Ready, Connecting and TransientFailure. Other states,
+// Idle and Shutdown are transitioned into by ClientConn; in the beginning of the connection
+// before any subConn is created ClientConn is in idle state. In the end when ClientConn
+// closes it is in Shutdown state.
+//
+// recordTransition should only be called synchronously from the same goroutine.
+func (cse *connectivityStateEvaluator) recordTransition(oldState, newState connectivity.State) connectivity.State {
+	// Update counters.
+	for idx, state := range []connectivity.State{oldState, newState} {
+		updateVal := 2*uint64(idx) - 1 // -1 for oldState and +1 for new.
+		switch state {
+		case connectivity.Ready:
+			cse.numReady += updateVal
+		case connectivity.Connecting:
+			cse.numConnecting += updateVal
+		case connectivity.TransientFailure:
+			cse.numTransientFailure += updateVal
+		}
+	}
+
+	// Evaluate.
+	if cse.numReady > 0 {
+		return connectivity.Ready
+	}
+	if cse.numConnecting > 0 {
+		return connectivity.Connecting
+	}
+	return connectivity.TransientFailure
+}
diff --git a/go/vendor/google.golang.org/grpc/balancer/base/base.go b/go/vendor/google.golang.org/grpc/balancer/base/base.go
new file mode 100644
index 0000000..012ace2
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/balancer/base/base.go
@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package base defines a balancer base that can be used to build balancers with
+// different picking algorithms.
+//
+// The base balancer creates a new SubConn for each resolved address. The
+// provided picker will only be notified about READY SubConns.
+//
+// This package is the base of round_robin balancer, its purpose is to be used
+// to build round_robin like balancers with complex picking algorithms.
+// Balancers with more complicated logic should try to implement a balancer
+// builder from scratch.
+//
+// All APIs in this package are experimental.
+package base
+
+import (
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/resolver"
+)
+
+// PickerBuilder creates balancer.Picker.
+type PickerBuilder interface {
+	// Build takes a slice of ready SubConns, and returns a picker that will be
+	// used by gRPC to pick a SubConn.
+	Build(readySCs map[resolver.Address]balancer.SubConn) balancer.Picker
+}
+
+// NewBalancerBuilder returns a balancer builder. The balancers
+// built by this builder will use the picker builder to build pickers.
+func NewBalancerBuilder(name string, pb PickerBuilder) balancer.Builder {
+	return &baseBuilder{
+		name:          name,
+		pickerBuilder: pb,
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go b/go/vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go
new file mode 100644
index 0000000..2eda0a1
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go
@@ -0,0 +1,79 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package roundrobin defines a roundrobin balancer. Roundrobin balancer is
+// installed as one of the default balancers in gRPC, users don't need to
+// explicitly install this balancer.
+package roundrobin
+
+import (
+	"sync"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/balancer/base"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+)
+
+// Name is the name of round_robin balancer.
+const Name = "round_robin"
+
+// newBuilder creates a new roundrobin balancer builder.
+func newBuilder() balancer.Builder {
+	return base.NewBalancerBuilder(Name, &rrPickerBuilder{})
+}
+
+func init() {
+	balancer.Register(newBuilder())
+}
+
+type rrPickerBuilder struct{}
+
+func (*rrPickerBuilder) Build(readySCs map[resolver.Address]balancer.SubConn) balancer.Picker {
+	grpclog.Infof("roundrobinPicker: newPicker called with readySCs: %v", readySCs)
+	var scs []balancer.SubConn
+	for _, sc := range readySCs {
+		scs = append(scs, sc)
+	}
+	return &rrPicker{
+		subConns: scs,
+	}
+}
+
+type rrPicker struct {
+	// subConns is the snapshot of the roundrobin balancer when this picker was
+	// created. The slice is immutable. Each Get() will do a round robin
+	// selection from it and return the selected SubConn.
+	subConns []balancer.SubConn
+
+	mu   sync.Mutex
+	next int
+}
+
+func (p *rrPicker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	if len(p.subConns) <= 0 {
+		return nil, nil, balancer.ErrNoSubConnAvailable
+	}
+
+	p.mu.Lock()
+	sc := p.subConns[p.next]
+	p.next = (p.next + 1) % len(p.subConns)
+	p.mu.Unlock()
+	return sc, nil, nil
+}
diff --git a/go/vendor/google.golang.org/grpc/balancer_conn_wrappers.go b/go/vendor/google.golang.org/grpc/balancer_conn_wrappers.go
new file mode 100644
index 0000000..1ab95fd
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/balancer_conn_wrappers.go
@@ -0,0 +1,301 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"fmt"
+	"sync"
+
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+)
+
+// scStateUpdate contains the subConn and the new state it changed to.
+type scStateUpdate struct {
+	sc    balancer.SubConn
+	state connectivity.State
+}
+
+// scStateUpdateBuffer is an unbounded channel for scStateChangeTuple.
+// TODO make a general purpose buffer that uses interface{}.
+type scStateUpdateBuffer struct {
+	c       chan *scStateUpdate
+	mu      sync.Mutex
+	backlog []*scStateUpdate
+}
+
+func newSCStateUpdateBuffer() *scStateUpdateBuffer {
+	return &scStateUpdateBuffer{
+		c: make(chan *scStateUpdate, 1),
+	}
+}
+
+func (b *scStateUpdateBuffer) put(t *scStateUpdate) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if len(b.backlog) == 0 {
+		select {
+		case b.c <- t:
+			return
+		default:
+		}
+	}
+	b.backlog = append(b.backlog, t)
+}
+
+func (b *scStateUpdateBuffer) load() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if len(b.backlog) > 0 {
+		select {
+		case b.c <- b.backlog[0]:
+			b.backlog[0] = nil
+			b.backlog = b.backlog[1:]
+		default:
+		}
+	}
+}
+
+// get returns the channel that the scStateUpdate will be sent to.
+//
+// Upon receiving, the caller should call load to send another
+// scStateChangeTuple onto the channel if there is any.
+func (b *scStateUpdateBuffer) get() <-chan *scStateUpdate {
+	return b.c
+}
+
+// resolverUpdate contains the new resolved addresses or error if there's
+// any.
+type resolverUpdate struct {
+	addrs []resolver.Address
+	err   error
+}
+
+// ccBalancerWrapper is a wrapper on top of cc for balancers.
+// It implements balancer.ClientConn interface.
+type ccBalancerWrapper struct {
+	cc               *ClientConn
+	balancer         balancer.Balancer
+	stateChangeQueue *scStateUpdateBuffer
+	resolverUpdateCh chan *resolverUpdate
+	done             chan struct{}
+
+	mu       sync.Mutex
+	subConns map[*acBalancerWrapper]struct{}
+}
+
+func newCCBalancerWrapper(cc *ClientConn, b balancer.Builder, bopts balancer.BuildOptions) *ccBalancerWrapper {
+	ccb := &ccBalancerWrapper{
+		cc:               cc,
+		stateChangeQueue: newSCStateUpdateBuffer(),
+		resolverUpdateCh: make(chan *resolverUpdate, 1),
+		done:             make(chan struct{}),
+		subConns:         make(map[*acBalancerWrapper]struct{}),
+	}
+	go ccb.watcher()
+	ccb.balancer = b.Build(ccb, bopts)
+	return ccb
+}
+
+// watcher balancer functions sequentially, so the balancer can be implemented
+// lock-free.
+func (ccb *ccBalancerWrapper) watcher() {
+	for {
+		select {
+		case t := <-ccb.stateChangeQueue.get():
+			ccb.stateChangeQueue.load()
+			select {
+			case <-ccb.done:
+				ccb.balancer.Close()
+				return
+			default:
+			}
+			ccb.balancer.HandleSubConnStateChange(t.sc, t.state)
+		case t := <-ccb.resolverUpdateCh:
+			select {
+			case <-ccb.done:
+				ccb.balancer.Close()
+				return
+			default:
+			}
+			ccb.balancer.HandleResolvedAddrs(t.addrs, t.err)
+		case <-ccb.done:
+		}
+
+		select {
+		case <-ccb.done:
+			ccb.balancer.Close()
+			ccb.mu.Lock()
+			scs := ccb.subConns
+			ccb.subConns = nil
+			ccb.mu.Unlock()
+			for acbw := range scs {
+				ccb.cc.removeAddrConn(acbw.getAddrConn(), errConnDrain)
+			}
+			return
+		default:
+		}
+	}
+}
+
+func (ccb *ccBalancerWrapper) close() {
+	close(ccb.done)
+}
+
+func (ccb *ccBalancerWrapper) handleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+	// When updating addresses for a SubConn, if the address in use is not in
+	// the new addresses, the old ac will be tearDown() and a new ac will be
+	// created. tearDown() generates a state change with Shutdown state, we
+	// don't want the balancer to receive this state change. So before
+	// tearDown() on the old ac, ac.acbw (acWrapper) will be set to nil, and
+	// this function will be called with (nil, Shutdown). We don't need to call
+	// balancer method in this case.
+	if sc == nil {
+		return
+	}
+	ccb.stateChangeQueue.put(&scStateUpdate{
+		sc:    sc,
+		state: s,
+	})
+}
+
+func (ccb *ccBalancerWrapper) handleResolvedAddrs(addrs []resolver.Address, err error) {
+	select {
+	case <-ccb.resolverUpdateCh:
+	default:
+	}
+	ccb.resolverUpdateCh <- &resolverUpdate{
+		addrs: addrs,
+		err:   err,
+	}
+}
+
+func (ccb *ccBalancerWrapper) NewSubConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) {
+	if len(addrs) <= 0 {
+		return nil, fmt.Errorf("grpc: cannot create SubConn with empty address list")
+	}
+	ccb.mu.Lock()
+	defer ccb.mu.Unlock()
+	if ccb.subConns == nil {
+		return nil, fmt.Errorf("grpc: ClientConn balancer wrapper was closed")
+	}
+	ac, err := ccb.cc.newAddrConn(addrs, opts)
+	if err != nil {
+		return nil, err
+	}
+	acbw := &acBalancerWrapper{ac: ac}
+	acbw.ac.mu.Lock()
+	ac.acbw = acbw
+	acbw.ac.mu.Unlock()
+	ccb.subConns[acbw] = struct{}{}
+	return acbw, nil
+}
+
+func (ccb *ccBalancerWrapper) RemoveSubConn(sc balancer.SubConn) {
+	acbw, ok := sc.(*acBalancerWrapper)
+	if !ok {
+		return
+	}
+	ccb.mu.Lock()
+	defer ccb.mu.Unlock()
+	if ccb.subConns == nil {
+		return
+	}
+	delete(ccb.subConns, acbw)
+	ccb.cc.removeAddrConn(acbw.getAddrConn(), errConnDrain)
+}
+
+func (ccb *ccBalancerWrapper) UpdateBalancerState(s connectivity.State, p balancer.Picker) {
+	ccb.mu.Lock()
+	defer ccb.mu.Unlock()
+	if ccb.subConns == nil {
+		return
+	}
+	ccb.cc.csMgr.updateState(s)
+	ccb.cc.blockingpicker.updatePicker(p)
+}
+
+func (ccb *ccBalancerWrapper) ResolveNow(o resolver.ResolveNowOption) {
+	ccb.cc.resolveNow(o)
+}
+
+func (ccb *ccBalancerWrapper) Target() string {
+	return ccb.cc.target
+}
+
+// acBalancerWrapper is a wrapper on top of ac for balancers.
+// It implements balancer.SubConn interface.
+type acBalancerWrapper struct {
+	mu sync.Mutex
+	ac *addrConn
+}
+
+func (acbw *acBalancerWrapper) UpdateAddresses(addrs []resolver.Address) {
+	acbw.mu.Lock()
+	defer acbw.mu.Unlock()
+	if len(addrs) <= 0 {
+		acbw.ac.tearDown(errConnDrain)
+		return
+	}
+	if !acbw.ac.tryUpdateAddrs(addrs) {
+		cc := acbw.ac.cc
+		opts := acbw.ac.scopts
+		acbw.ac.mu.Lock()
+		// Set old ac.acbw to nil so the Shutdown state update will be ignored
+		// by balancer.
+		//
+		// TODO(bar) the state transition could be wrong when tearDown() old ac
+		// and creating new ac, fix the transition.
+		acbw.ac.acbw = nil
+		acbw.ac.mu.Unlock()
+		acState := acbw.ac.getState()
+		acbw.ac.tearDown(errConnDrain)
+
+		if acState == connectivity.Shutdown {
+			return
+		}
+
+		ac, err := cc.newAddrConn(addrs, opts)
+		if err != nil {
+			grpclog.Warningf("acBalancerWrapper: UpdateAddresses: failed to newAddrConn: %v", err)
+			return
+		}
+		acbw.ac = ac
+		ac.mu.Lock()
+		ac.acbw = acbw
+		ac.mu.Unlock()
+		if acState != connectivity.Idle {
+			ac.connect()
+		}
+	}
+}
+
+func (acbw *acBalancerWrapper) Connect() {
+	acbw.mu.Lock()
+	defer acbw.mu.Unlock()
+	acbw.ac.connect()
+}
+
+func (acbw *acBalancerWrapper) getAddrConn() *addrConn {
+	acbw.mu.Lock()
+	defer acbw.mu.Unlock()
+	return acbw.ac
+}
diff --git a/go/vendor/google.golang.org/grpc/balancer_v1_wrapper.go b/go/vendor/google.golang.org/grpc/balancer_v1_wrapper.go
new file mode 100644
index 0000000..e0ce32c
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/balancer_v1_wrapper.go
@@ -0,0 +1,328 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"strings"
+	"sync"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/status"
+)
+
+type balancerWrapperBuilder struct {
+	b Balancer // The v1 balancer.
+}
+
+func (bwb *balancerWrapperBuilder) Build(cc balancer.ClientConn, opts balancer.BuildOptions) balancer.Balancer {
+	targetAddr := cc.Target()
+	targetSplitted := strings.Split(targetAddr, ":///")
+	if len(targetSplitted) >= 2 {
+		targetAddr = targetSplitted[1]
+	}
+
+	bwb.b.Start(targetAddr, BalancerConfig{
+		DialCreds: opts.DialCreds,
+		Dialer:    opts.Dialer,
+	})
+	_, pickfirst := bwb.b.(*pickFirst)
+	bw := &balancerWrapper{
+		balancer:   bwb.b,
+		pickfirst:  pickfirst,
+		cc:         cc,
+		targetAddr: targetAddr,
+		startCh:    make(chan struct{}),
+		conns:      make(map[resolver.Address]balancer.SubConn),
+		connSt:     make(map[balancer.SubConn]*scState),
+		csEvltr:    &balancer.ConnectivityStateEvaluator{},
+		state:      connectivity.Idle,
+	}
+	cc.UpdateBalancerState(connectivity.Idle, bw)
+	go bw.lbWatcher()
+	return bw
+}
+
+func (bwb *balancerWrapperBuilder) Name() string {
+	return "wrapper"
+}
+
+type scState struct {
+	addr Address // The v1 address type.
+	s    connectivity.State
+	down func(error)
+}
+
+type balancerWrapper struct {
+	balancer  Balancer // The v1 balancer.
+	pickfirst bool
+
+	cc         balancer.ClientConn
+	targetAddr string // Target without the scheme.
+
+	mu     sync.Mutex
+	conns  map[resolver.Address]balancer.SubConn
+	connSt map[balancer.SubConn]*scState
+	// This channel is closed when handling the first resolver result.
+	// lbWatcher blocks until this is closed, to avoid race between
+	// - NewSubConn is created, cc wants to notify balancer of state changes;
+	// - Build hasn't return, cc doesn't have access to balancer.
+	startCh chan struct{}
+
+	// To aggregate the connectivity state.
+	csEvltr *balancer.ConnectivityStateEvaluator
+	state   connectivity.State
+}
+
+// lbWatcher watches the Notify channel of the balancer and manages
+// connections accordingly.
+func (bw *balancerWrapper) lbWatcher() {
+	<-bw.startCh
+	notifyCh := bw.balancer.Notify()
+	if notifyCh == nil {
+		// There's no resolver in the balancer. Connect directly.
+		a := resolver.Address{
+			Addr: bw.targetAddr,
+			Type: resolver.Backend,
+		}
+		sc, err := bw.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{})
+		if err != nil {
+			grpclog.Warningf("Error creating connection to %v. Err: %v", a, err)
+		} else {
+			bw.mu.Lock()
+			bw.conns[a] = sc
+			bw.connSt[sc] = &scState{
+				addr: Address{Addr: bw.targetAddr},
+				s:    connectivity.Idle,
+			}
+			bw.mu.Unlock()
+			sc.Connect()
+		}
+		return
+	}
+
+	for addrs := range notifyCh {
+		grpclog.Infof("balancerWrapper: got update addr from Notify: %v\n", addrs)
+		if bw.pickfirst {
+			var (
+				oldA  resolver.Address
+				oldSC balancer.SubConn
+			)
+			bw.mu.Lock()
+			for oldA, oldSC = range bw.conns {
+				break
+			}
+			bw.mu.Unlock()
+			if len(addrs) <= 0 {
+				if oldSC != nil {
+					// Teardown old sc.
+					bw.mu.Lock()
+					delete(bw.conns, oldA)
+					delete(bw.connSt, oldSC)
+					bw.mu.Unlock()
+					bw.cc.RemoveSubConn(oldSC)
+				}
+				continue
+			}
+
+			var newAddrs []resolver.Address
+			for _, a := range addrs {
+				newAddr := resolver.Address{
+					Addr:       a.Addr,
+					Type:       resolver.Backend, // All addresses from balancer are all backends.
+					ServerName: "",
+					Metadata:   a.Metadata,
+				}
+				newAddrs = append(newAddrs, newAddr)
+			}
+			if oldSC == nil {
+				// Create new sc.
+				sc, err := bw.cc.NewSubConn(newAddrs, balancer.NewSubConnOptions{})
+				if err != nil {
+					grpclog.Warningf("Error creating connection to %v. Err: %v", newAddrs, err)
+				} else {
+					bw.mu.Lock()
+					// For pickfirst, there should be only one SubConn, so the
+					// address doesn't matter. All states updating (up and down)
+					// and picking should all happen on that only SubConn.
+					bw.conns[resolver.Address{}] = sc
+					bw.connSt[sc] = &scState{
+						addr: addrs[0], // Use the first address.
+						s:    connectivity.Idle,
+					}
+					bw.mu.Unlock()
+					sc.Connect()
+				}
+			} else {
+				bw.mu.Lock()
+				bw.connSt[oldSC].addr = addrs[0]
+				bw.mu.Unlock()
+				oldSC.UpdateAddresses(newAddrs)
+			}
+		} else {
+			var (
+				add []resolver.Address // Addresses need to setup connections.
+				del []balancer.SubConn // Connections need to tear down.
+			)
+			resAddrs := make(map[resolver.Address]Address)
+			for _, a := range addrs {
+				resAddrs[resolver.Address{
+					Addr:       a.Addr,
+					Type:       resolver.Backend, // All addresses from balancer are all backends.
+					ServerName: "",
+					Metadata:   a.Metadata,
+				}] = a
+			}
+			bw.mu.Lock()
+			for a := range resAddrs {
+				if _, ok := bw.conns[a]; !ok {
+					add = append(add, a)
+				}
+			}
+			for a, c := range bw.conns {
+				if _, ok := resAddrs[a]; !ok {
+					del = append(del, c)
+					delete(bw.conns, a)
+					// Keep the state of this sc in bw.connSt until its state becomes Shutdown.
+				}
+			}
+			bw.mu.Unlock()
+			for _, a := range add {
+				sc, err := bw.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{})
+				if err != nil {
+					grpclog.Warningf("Error creating connection to %v. Err: %v", a, err)
+				} else {
+					bw.mu.Lock()
+					bw.conns[a] = sc
+					bw.connSt[sc] = &scState{
+						addr: resAddrs[a],
+						s:    connectivity.Idle,
+					}
+					bw.mu.Unlock()
+					sc.Connect()
+				}
+			}
+			for _, c := range del {
+				bw.cc.RemoveSubConn(c)
+			}
+		}
+	}
+}
+
+func (bw *balancerWrapper) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+	bw.mu.Lock()
+	defer bw.mu.Unlock()
+	scSt, ok := bw.connSt[sc]
+	if !ok {
+		return
+	}
+	if s == connectivity.Idle {
+		sc.Connect()
+	}
+	oldS := scSt.s
+	scSt.s = s
+	if oldS != connectivity.Ready && s == connectivity.Ready {
+		scSt.down = bw.balancer.Up(scSt.addr)
+	} else if oldS == connectivity.Ready && s != connectivity.Ready {
+		if scSt.down != nil {
+			scSt.down(errConnClosing)
+		}
+	}
+	sa := bw.csEvltr.RecordTransition(oldS, s)
+	if bw.state != sa {
+		bw.state = sa
+	}
+	bw.cc.UpdateBalancerState(bw.state, bw)
+	if s == connectivity.Shutdown {
+		// Remove state for this sc.
+		delete(bw.connSt, sc)
+	}
+}
+
+func (bw *balancerWrapper) HandleResolvedAddrs([]resolver.Address, error) {
+	bw.mu.Lock()
+	defer bw.mu.Unlock()
+	select {
+	case <-bw.startCh:
+	default:
+		close(bw.startCh)
+	}
+	// There should be a resolver inside the balancer.
+	// All updates here, if any, are ignored.
+}
+
+func (bw *balancerWrapper) Close() {
+	bw.mu.Lock()
+	defer bw.mu.Unlock()
+	select {
+	case <-bw.startCh:
+	default:
+		close(bw.startCh)
+	}
+	bw.balancer.Close()
+}
+
+// The picker is the balancerWrapper itself.
+// Pick should never return ErrNoSubConnAvailable.
+// It either blocks or returns error, consistent with v1 balancer Get().
+func (bw *balancerWrapper) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	failfast := true // Default failfast is true.
+	if ss, ok := rpcInfoFromContext(ctx); ok {
+		failfast = ss.failfast
+	}
+	a, p, err := bw.balancer.Get(ctx, BalancerGetOptions{BlockingWait: !failfast})
+	if err != nil {
+		return nil, nil, err
+	}
+	var done func(balancer.DoneInfo)
+	if p != nil {
+		done = func(i balancer.DoneInfo) { p() }
+	}
+	var sc balancer.SubConn
+	bw.mu.Lock()
+	defer bw.mu.Unlock()
+	if bw.pickfirst {
+		// Get the first sc in conns.
+		for _, sc = range bw.conns {
+			break
+		}
+	} else {
+		var ok bool
+		sc, ok = bw.conns[resolver.Address{
+			Addr:       a.Addr,
+			Type:       resolver.Backend,
+			ServerName: "",
+			Metadata:   a.Metadata,
+		}]
+		if !ok && failfast {
+			return nil, nil, status.Errorf(codes.Unavailable, "there is no connection available")
+		}
+		if s, ok := bw.connSt[sc]; failfast && (!ok || s.s != connectivity.Ready) {
+			// If the returned sc is not ready and RPC is failfast,
+			// return error, and this RPC will fail.
+			return nil, nil, status.Errorf(codes.Unavailable, "there is no connection available")
+		}
+	}
+
+	return sc, done, nil
+}
diff --git a/go/vendor/google.golang.org/grpc/call.go b/go/vendor/google.golang.org/grpc/call.go
new file mode 100644
index 0000000..180d79d
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/call.go
@@ -0,0 +1,74 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"golang.org/x/net/context"
+)
+
+// Invoke sends the RPC request on the wire and returns after response is
+// received.  This is typically called by generated code.
+//
+// All errors returned by Invoke are compatible with the status package.
+func (cc *ClientConn) Invoke(ctx context.Context, method string, args, reply interface{}, opts ...CallOption) error {
+	// allow interceptor to see all applicable call options, which means those
+	// configured as defaults from dial option as well as per-call options
+	opts = combine(cc.dopts.callOptions, opts)
+
+	if cc.dopts.unaryInt != nil {
+		return cc.dopts.unaryInt(ctx, method, args, reply, cc, invoke, opts...)
+	}
+	return invoke(ctx, method, args, reply, cc, opts...)
+}
+
+func combine(o1 []CallOption, o2 []CallOption) []CallOption {
+	// we don't use append because o1 could have extra capacity whose
+	// elements would be overwritten, which could cause inadvertent
+	// sharing (and race connditions) between concurrent calls
+	if len(o1) == 0 {
+		return o2
+	} else if len(o2) == 0 {
+		return o1
+	}
+	ret := make([]CallOption, len(o1)+len(o2))
+	copy(ret, o1)
+	copy(ret[len(o1):], o2)
+	return ret
+}
+
+// Invoke sends the RPC request on the wire and returns after response is
+// received.  This is typically called by generated code.
+//
+// DEPRECATED: Use ClientConn.Invoke instead.
+func Invoke(ctx context.Context, method string, args, reply interface{}, cc *ClientConn, opts ...CallOption) error {
+	return cc.Invoke(ctx, method, args, reply, opts...)
+}
+
+var unaryStreamDesc = &StreamDesc{ServerStreams: false, ClientStreams: false}
+
+func invoke(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, opts ...CallOption) error {
+	cs, err := newClientStream(ctx, unaryStreamDesc, cc, method, opts...)
+	if err != nil {
+		return err
+	}
+	if err := cs.SendMsg(req); err != nil {
+		return err
+	}
+	return cs.RecvMsg(reply)
+}
diff --git a/go/vendor/google.golang.org/grpc/clientconn.go b/go/vendor/google.golang.org/grpc/clientconn.go
new file mode 100644
index 0000000..f49ac3f
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/clientconn.go
@@ -0,0 +1,1398 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"net"
+	"reflect"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/balancer"
+	_ "google.golang.org/grpc/balancer/roundrobin" // To register roundrobin.
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/backoff"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/resolver"
+	_ "google.golang.org/grpc/resolver/dns"         // To register dns resolver.
+	_ "google.golang.org/grpc/resolver/passthrough" // To register passthrough resolver.
+	"google.golang.org/grpc/status"
+)
+
+const (
+	// minimum time to give a connection to complete
+	minConnectTimeout = 20 * time.Second
+	// must match grpclbName in grpclb/grpclb.go
+	grpclbName = "grpclb"
+)
+
+var (
+	// ErrClientConnClosing indicates that the operation is illegal because
+	// the ClientConn is closing.
+	//
+	// Deprecated: this error should not be relied upon by users; use the status
+	// code of Canceled instead.
+	ErrClientConnClosing = status.Error(codes.Canceled, "grpc: the client connection is closing")
+	// errConnDrain indicates that the connection starts to be drained and does not accept any new RPCs.
+	errConnDrain = errors.New("grpc: the connection is drained")
+	// errConnClosing indicates that the connection is closing.
+	errConnClosing = errors.New("grpc: the connection is closing")
+	// errBalancerClosed indicates that the balancer is closed.
+	errBalancerClosed = errors.New("grpc: balancer is closed")
+	// We use an accessor so that minConnectTimeout can be
+	// atomically read and updated while testing.
+	getMinConnectTimeout = func() time.Duration {
+		return minConnectTimeout
+	}
+)
+
+// The following errors are returned from Dial and DialContext
+var (
+	// errNoTransportSecurity indicates that there is no transport security
+	// being set for ClientConn. Users should either set one or explicitly
+	// call WithInsecure DialOption to disable security.
+	errNoTransportSecurity = errors.New("grpc: no transport security set (use grpc.WithInsecure() explicitly or set credentials)")
+	// errTransportCredsAndBundle indicates that creds bundle is used together
+	// with other individual Transport Credentials.
+	errTransportCredsAndBundle = errors.New("grpc: credentials.Bundle may not be used with individual TransportCredentials")
+	// errTransportCredentialsMissing indicates that users want to transmit security
+	// information (e.g., oauth2 token) which requires secure connection on an insecure
+	// connection.
+	errTransportCredentialsMissing = errors.New("grpc: the credentials require transport level security (use grpc.WithTransportCredentials() to set)")
+	// errCredentialsConflict indicates that grpc.WithTransportCredentials()
+	// and grpc.WithInsecure() are both called for a connection.
+	errCredentialsConflict = errors.New("grpc: transport credentials are set for an insecure connection (grpc.WithTransportCredentials() and grpc.WithInsecure() are both called)")
+)
+
+const (
+	defaultClientMaxReceiveMessageSize = 1024 * 1024 * 4
+	defaultClientMaxSendMessageSize    = math.MaxInt32
+	// http2IOBufSize specifies the buffer size for sending frames.
+	defaultWriteBufSize = 32 * 1024
+	defaultReadBufSize  = 32 * 1024
+)
+
+// Dial creates a client connection to the given target.
+func Dial(target string, opts ...DialOption) (*ClientConn, error) {
+	return DialContext(context.Background(), target, opts...)
+}
+
+// DialContext creates a client connection to the given target. By default, it's
+// a non-blocking dial (the function won't wait for connections to be
+// established, and connecting happens in the background). To make it a blocking
+// dial, use WithBlock() dial option.
+//
+// In the non-blocking case, the ctx does not act against the connection. It
+// only controls the setup steps.
+//
+// In the blocking case, ctx can be used to cancel or expire the pending
+// connection. Once this function returns, the cancellation and expiration of
+// ctx will be noop. Users should call ClientConn.Close to terminate all the
+// pending operations after this function returns.
+//
+// The target name syntax is defined in
+// https://github.com/grpc/grpc/blob/master/doc/naming.md.
+// e.g. to use dns resolver, a "dns:///" prefix should be applied to the target.
+func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *ClientConn, err error) {
+	cc := &ClientConn{
+		target:         target,
+		csMgr:          &connectivityStateManager{},
+		conns:          make(map[*addrConn]struct{}),
+		dopts:          defaultDialOptions(),
+		blockingpicker: newPickerWrapper(),
+		czData:         new(channelzData),
+	}
+	cc.retryThrottler.Store((*retryThrottler)(nil))
+	cc.ctx, cc.cancel = context.WithCancel(context.Background())
+
+	for _, opt := range opts {
+		opt.apply(&cc.dopts)
+	}
+
+	if channelz.IsOn() {
+		if cc.dopts.channelzParentID != 0 {
+			cc.channelzID = channelz.RegisterChannel(&channelzChannel{cc}, cc.dopts.channelzParentID, target)
+			channelz.AddTraceEvent(cc.channelzID, &channelz.TraceEventDesc{
+				Desc:     "Channel Created",
+				Severity: channelz.CtINFO,
+				Parent: &channelz.TraceEventDesc{
+					Desc:     fmt.Sprintf("Nested Channel(id:%d) created", cc.channelzID),
+					Severity: channelz.CtINFO,
+				},
+			})
+		} else {
+			cc.channelzID = channelz.RegisterChannel(&channelzChannel{cc}, 0, target)
+			channelz.AddTraceEvent(cc.channelzID, &channelz.TraceEventDesc{
+				Desc:     "Channel Created",
+				Severity: channelz.CtINFO,
+			})
+		}
+		cc.csMgr.channelzID = cc.channelzID
+	}
+
+	if !cc.dopts.insecure {
+		if cc.dopts.copts.TransportCredentials == nil && cc.dopts.copts.CredsBundle == nil {
+			return nil, errNoTransportSecurity
+		}
+		if cc.dopts.copts.TransportCredentials != nil && cc.dopts.copts.CredsBundle != nil {
+			return nil, errTransportCredsAndBundle
+		}
+	} else {
+		if cc.dopts.copts.TransportCredentials != nil || cc.dopts.copts.CredsBundle != nil {
+			return nil, errCredentialsConflict
+		}
+		for _, cd := range cc.dopts.copts.PerRPCCredentials {
+			if cd.RequireTransportSecurity() {
+				return nil, errTransportCredentialsMissing
+			}
+		}
+	}
+
+	cc.mkp = cc.dopts.copts.KeepaliveParams
+
+	if cc.dopts.copts.Dialer == nil {
+		cc.dopts.copts.Dialer = newProxyDialer(
+			func(ctx context.Context, addr string) (net.Conn, error) {
+				network, addr := parseDialTarget(addr)
+				return dialContext(ctx, network, addr)
+			},
+		)
+	}
+
+	if cc.dopts.copts.UserAgent != "" {
+		cc.dopts.copts.UserAgent += " " + grpcUA
+	} else {
+		cc.dopts.copts.UserAgent = grpcUA
+	}
+
+	if cc.dopts.timeout > 0 {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithTimeout(ctx, cc.dopts.timeout)
+		defer cancel()
+	}
+
+	defer func() {
+		select {
+		case <-ctx.Done():
+			conn, err = nil, ctx.Err()
+		default:
+		}
+
+		if err != nil {
+			cc.Close()
+		}
+	}()
+
+	scSet := false
+	if cc.dopts.scChan != nil {
+		// Try to get an initial service config.
+		select {
+		case sc, ok := <-cc.dopts.scChan:
+			if ok {
+				cc.sc = sc
+				scSet = true
+			}
+		default:
+		}
+	}
+	if cc.dopts.bs == nil {
+		cc.dopts.bs = backoff.Exponential{
+			MaxDelay: DefaultBackoffConfig.MaxDelay,
+		}
+	}
+	if cc.dopts.resolverBuilder == nil {
+		// Only try to parse target when resolver builder is not already set.
+		cc.parsedTarget = parseTarget(cc.target)
+		grpclog.Infof("parsed scheme: %q", cc.parsedTarget.Scheme)
+		cc.dopts.resolverBuilder = resolver.Get(cc.parsedTarget.Scheme)
+		if cc.dopts.resolverBuilder == nil {
+			// If resolver builder is still nil, the parse target's scheme is
+			// not registered. Fallback to default resolver and set Endpoint to
+			// the original unparsed target.
+			grpclog.Infof("scheme %q not registered, fallback to default scheme", cc.parsedTarget.Scheme)
+			cc.parsedTarget = resolver.Target{
+				Scheme:   resolver.GetDefaultScheme(),
+				Endpoint: target,
+			}
+			cc.dopts.resolverBuilder = resolver.Get(cc.parsedTarget.Scheme)
+		}
+	} else {
+		cc.parsedTarget = resolver.Target{Endpoint: target}
+	}
+	creds := cc.dopts.copts.TransportCredentials
+	if creds != nil && creds.Info().ServerName != "" {
+		cc.authority = creds.Info().ServerName
+	} else if cc.dopts.insecure && cc.dopts.authority != "" {
+		cc.authority = cc.dopts.authority
+	} else {
+		// Use endpoint from "scheme://authority/endpoint" as the default
+		// authority for ClientConn.
+		cc.authority = cc.parsedTarget.Endpoint
+	}
+
+	if cc.dopts.scChan != nil && !scSet {
+		// Blocking wait for the initial service config.
+		select {
+		case sc, ok := <-cc.dopts.scChan:
+			if ok {
+				cc.sc = sc
+			}
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+	}
+	if cc.dopts.scChan != nil {
+		go cc.scWatcher()
+	}
+
+	var credsClone credentials.TransportCredentials
+	if creds := cc.dopts.copts.TransportCredentials; creds != nil {
+		credsClone = creds.Clone()
+	}
+	cc.balancerBuildOpts = balancer.BuildOptions{
+		DialCreds:        credsClone,
+		CredsBundle:      cc.dopts.copts.CredsBundle,
+		Dialer:           cc.dopts.copts.Dialer,
+		ChannelzParentID: cc.channelzID,
+	}
+
+	// Build the resolver.
+	cc.resolverWrapper, err = newCCResolverWrapper(cc)
+	if err != nil {
+		return nil, fmt.Errorf("failed to build resolver: %v", err)
+	}
+	// Start the resolver wrapper goroutine after resolverWrapper is created.
+	//
+	// If the goroutine is started before resolverWrapper is ready, the
+	// following may happen: The goroutine sends updates to cc. cc forwards
+	// those to balancer. Balancer creates new addrConn. addrConn fails to
+	// connect, and calls resolveNow(). resolveNow() tries to use the non-ready
+	// resolverWrapper.
+	cc.resolverWrapper.start()
+
+	// A blocking dial blocks until the clientConn is ready.
+	if cc.dopts.block {
+		for {
+			s := cc.GetState()
+			if s == connectivity.Ready {
+				break
+			} else if cc.dopts.copts.FailOnNonTempDialError && s == connectivity.TransientFailure {
+				if err = cc.blockingpicker.connectionError(); err != nil {
+					terr, ok := err.(interface{ Temporary() bool })
+					if ok && !terr.Temporary() {
+						return nil, err
+					}
+				}
+			}
+			if !cc.WaitForStateChange(ctx, s) {
+				// ctx got timeout or canceled.
+				return nil, ctx.Err()
+			}
+		}
+	}
+
+	return cc, nil
+}
+
+// connectivityStateManager keeps the connectivity.State of ClientConn.
+// This struct will eventually be exported so the balancers can access it.
+type connectivityStateManager struct {
+	mu         sync.Mutex
+	state      connectivity.State
+	notifyChan chan struct{}
+	channelzID int64
+}
+
+// updateState updates the connectivity.State of ClientConn.
+// If there's a change it notifies goroutines waiting on state change to
+// happen.
+func (csm *connectivityStateManager) updateState(state connectivity.State) {
+	csm.mu.Lock()
+	defer csm.mu.Unlock()
+	if csm.state == connectivity.Shutdown {
+		return
+	}
+	if csm.state == state {
+		return
+	}
+	csm.state = state
+	if channelz.IsOn() {
+		channelz.AddTraceEvent(csm.channelzID, &channelz.TraceEventDesc{
+			Desc:     fmt.Sprintf("Channel Connectivity change to %v", state),
+			Severity: channelz.CtINFO,
+		})
+	}
+	if csm.notifyChan != nil {
+		// There are other goroutines waiting on this channel.
+		close(csm.notifyChan)
+		csm.notifyChan = nil
+	}
+}
+
+func (csm *connectivityStateManager) getState() connectivity.State {
+	csm.mu.Lock()
+	defer csm.mu.Unlock()
+	return csm.state
+}
+
+func (csm *connectivityStateManager) getNotifyChan() <-chan struct{} {
+	csm.mu.Lock()
+	defer csm.mu.Unlock()
+	if csm.notifyChan == nil {
+		csm.notifyChan = make(chan struct{})
+	}
+	return csm.notifyChan
+}
+
+// ClientConn represents a client connection to an RPC server.
+type ClientConn struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	target       string
+	parsedTarget resolver.Target
+	authority    string
+	dopts        dialOptions
+	csMgr        *connectivityStateManager
+
+	balancerBuildOpts balancer.BuildOptions
+	resolverWrapper   *ccResolverWrapper
+	blockingpicker    *pickerWrapper
+
+	mu    sync.RWMutex
+	sc    ServiceConfig
+	scRaw string
+	conns map[*addrConn]struct{}
+	// Keepalive parameter can be updated if a GoAway is received.
+	mkp             keepalive.ClientParameters
+	curBalancerName string
+	preBalancerName string // previous balancer name.
+	curAddresses    []resolver.Address
+	balancerWrapper *ccBalancerWrapper
+	retryThrottler  atomic.Value
+
+	channelzID int64 // channelz unique identification number
+	czData     *channelzData
+}
+
+// WaitForStateChange waits until the connectivity.State of ClientConn changes from sourceState or
+// ctx expires. A true value is returned in former case and false in latter.
+// This is an EXPERIMENTAL API.
+func (cc *ClientConn) WaitForStateChange(ctx context.Context, sourceState connectivity.State) bool {
+	ch := cc.csMgr.getNotifyChan()
+	if cc.csMgr.getState() != sourceState {
+		return true
+	}
+	select {
+	case <-ctx.Done():
+		return false
+	case <-ch:
+		return true
+	}
+}
+
+// GetState returns the connectivity.State of ClientConn.
+// This is an EXPERIMENTAL API.
+func (cc *ClientConn) GetState() connectivity.State {
+	return cc.csMgr.getState()
+}
+
+func (cc *ClientConn) scWatcher() {
+	for {
+		select {
+		case sc, ok := <-cc.dopts.scChan:
+			if !ok {
+				return
+			}
+			cc.mu.Lock()
+			// TODO: load balance policy runtime change is ignored.
+			// We may revist this decision in the future.
+			cc.sc = sc
+			cc.scRaw = ""
+			cc.mu.Unlock()
+		case <-cc.ctx.Done():
+			return
+		}
+	}
+}
+
+func (cc *ClientConn) handleResolvedAddrs(addrs []resolver.Address, err error) {
+	cc.mu.Lock()
+	defer cc.mu.Unlock()
+	if cc.conns == nil {
+		// cc was closed.
+		return
+	}
+
+	if reflect.DeepEqual(cc.curAddresses, addrs) {
+		return
+	}
+
+	cc.curAddresses = addrs
+
+	if cc.dopts.balancerBuilder == nil {
+		// Only look at balancer types and switch balancer if balancer dial
+		// option is not set.
+		var isGRPCLB bool
+		for _, a := range addrs {
+			if a.Type == resolver.GRPCLB {
+				isGRPCLB = true
+				break
+			}
+		}
+		var newBalancerName string
+		if isGRPCLB {
+			newBalancerName = grpclbName
+		} else {
+			// Address list doesn't contain grpclb address. Try to pick a
+			// non-grpclb balancer.
+			newBalancerName = cc.curBalancerName
+			// If current balancer is grpclb, switch to the previous one.
+			if newBalancerName == grpclbName {
+				newBalancerName = cc.preBalancerName
+			}
+			// The following could be true in two cases:
+			// - the first time handling resolved addresses
+			//   (curBalancerName="")
+			// - the first time handling non-grpclb addresses
+			//   (curBalancerName="grpclb", preBalancerName="")
+			if newBalancerName == "" {
+				newBalancerName = PickFirstBalancerName
+			}
+		}
+		cc.switchBalancer(newBalancerName)
+	} else if cc.balancerWrapper == nil {
+		// Balancer dial option was set, and this is the first time handling
+		// resolved addresses. Build a balancer with dopts.balancerBuilder.
+		cc.balancerWrapper = newCCBalancerWrapper(cc, cc.dopts.balancerBuilder, cc.balancerBuildOpts)
+	}
+
+	cc.balancerWrapper.handleResolvedAddrs(addrs, nil)
+}
+
+// switchBalancer starts the switching from current balancer to the balancer
+// with the given name.
+//
+// It will NOT send the current address list to the new balancer. If needed,
+// caller of this function should send address list to the new balancer after
+// this function returns.
+//
+// Caller must hold cc.mu.
+func (cc *ClientConn) switchBalancer(name string) {
+	if cc.conns == nil {
+		return
+	}
+
+	if strings.ToLower(cc.curBalancerName) == strings.ToLower(name) {
+		return
+	}
+
+	grpclog.Infof("ClientConn switching balancer to %q", name)
+	if cc.dopts.balancerBuilder != nil {
+		grpclog.Infoln("ignoring balancer switching: Balancer DialOption used instead")
+		return
+	}
+	// TODO(bar switching) change this to two steps: drain and close.
+	// Keep track of sc in wrapper.
+	if cc.balancerWrapper != nil {
+		cc.balancerWrapper.close()
+	}
+
+	builder := balancer.Get(name)
+	// TODO(yuxuanli): If user send a service config that does not contain a valid balancer name, should
+	// we reuse previous one?
+	if channelz.IsOn() {
+		if builder == nil {
+			channelz.AddTraceEvent(cc.channelzID, &channelz.TraceEventDesc{
+				Desc:     fmt.Sprintf("Channel switches to new LB policy %q due to fallback from invalid balancer name", PickFirstBalancerName),
+				Severity: channelz.CtWarning,
+			})
+		} else {
+			channelz.AddTraceEvent(cc.channelzID, &channelz.TraceEventDesc{
+				Desc:     fmt.Sprintf("Channel switches to new LB policy %q", name),
+				Severity: channelz.CtINFO,
+			})
+		}
+	}
+	if builder == nil {
+		grpclog.Infof("failed to get balancer builder for: %v, using pick_first instead", name)
+		builder = newPickfirstBuilder()
+	}
+
+	cc.preBalancerName = cc.curBalancerName
+	cc.curBalancerName = builder.Name()
+	cc.balancerWrapper = newCCBalancerWrapper(cc, builder, cc.balancerBuildOpts)
+}
+
+func (cc *ClientConn) handleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+	cc.mu.Lock()
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return
+	}
+	// TODO(bar switching) send updates to all balancer wrappers when balancer
+	// gracefully switching is supported.
+	cc.balancerWrapper.handleSubConnStateChange(sc, s)
+	cc.mu.Unlock()
+}
+
+// newAddrConn creates an addrConn for addrs and adds it to cc.conns.
+//
+// Caller needs to make sure len(addrs) > 0.
+func (cc *ClientConn) newAddrConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (*addrConn, error) {
+	ac := &addrConn{
+		cc:                  cc,
+		addrs:               addrs,
+		scopts:              opts,
+		dopts:               cc.dopts,
+		czData:              new(channelzData),
+		successfulHandshake: true, // make the first nextAddr() call _not_ move addrIdx up by 1
+		resetBackoff:        make(chan struct{}),
+	}
+	ac.ctx, ac.cancel = context.WithCancel(cc.ctx)
+	// Track ac in cc. This needs to be done before any getTransport(...) is called.
+	cc.mu.Lock()
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return nil, ErrClientConnClosing
+	}
+	if channelz.IsOn() {
+		ac.channelzID = channelz.RegisterSubChannel(ac, cc.channelzID, "")
+		channelz.AddTraceEvent(ac.channelzID, &channelz.TraceEventDesc{
+			Desc:     "Subchannel Created",
+			Severity: channelz.CtINFO,
+			Parent: &channelz.TraceEventDesc{
+				Desc:     fmt.Sprintf("Subchannel(id:%d) created", ac.channelzID),
+				Severity: channelz.CtINFO,
+			},
+		})
+	}
+	cc.conns[ac] = struct{}{}
+	cc.mu.Unlock()
+	return ac, nil
+}
+
+// removeAddrConn removes the addrConn in the subConn from clientConn.
+// It also tears down the ac with the given error.
+func (cc *ClientConn) removeAddrConn(ac *addrConn, err error) {
+	cc.mu.Lock()
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return
+	}
+	delete(cc.conns, ac)
+	cc.mu.Unlock()
+	ac.tearDown(err)
+}
+
+func (cc *ClientConn) channelzMetric() *channelz.ChannelInternalMetric {
+	return &channelz.ChannelInternalMetric{
+		State:                    cc.GetState(),
+		Target:                   cc.target,
+		CallsStarted:             atomic.LoadInt64(&cc.czData.callsStarted),
+		CallsSucceeded:           atomic.LoadInt64(&cc.czData.callsSucceeded),
+		CallsFailed:              atomic.LoadInt64(&cc.czData.callsFailed),
+		LastCallStartedTimestamp: time.Unix(0, atomic.LoadInt64(&cc.czData.lastCallStartedTime)),
+	}
+}
+
+// Target returns the target string of the ClientConn.
+// This is an EXPERIMENTAL API.
+func (cc *ClientConn) Target() string {
+	return cc.target
+}
+
+func (cc *ClientConn) incrCallsStarted() {
+	atomic.AddInt64(&cc.czData.callsStarted, 1)
+	atomic.StoreInt64(&cc.czData.lastCallStartedTime, time.Now().UnixNano())
+}
+
+func (cc *ClientConn) incrCallsSucceeded() {
+	atomic.AddInt64(&cc.czData.callsSucceeded, 1)
+}
+
+func (cc *ClientConn) incrCallsFailed() {
+	atomic.AddInt64(&cc.czData.callsFailed, 1)
+}
+
+// connect starts creating a transport.
+// It does nothing if the ac is not IDLE.
+// TODO(bar) Move this to the addrConn section.
+func (ac *addrConn) connect() error {
+	ac.mu.Lock()
+	if ac.state == connectivity.Shutdown {
+		ac.mu.Unlock()
+		return errConnClosing
+	}
+	if ac.state != connectivity.Idle {
+		ac.mu.Unlock()
+		return nil
+	}
+	ac.updateConnectivityState(connectivity.Connecting)
+	ac.cc.handleSubConnStateChange(ac.acbw, ac.state)
+	ac.mu.Unlock()
+
+	// Start a goroutine connecting to the server asynchronously.
+	go ac.resetTransport(false)
+	return nil
+}
+
+// tryUpdateAddrs tries to update ac.addrs with the new addresses list.
+//
+// It checks whether current connected address of ac is in the new addrs list.
+//  - If true, it updates ac.addrs and returns true. The ac will keep using
+//    the existing connection.
+//  - If false, it does nothing and returns false.
+func (ac *addrConn) tryUpdateAddrs(addrs []resolver.Address) bool {
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	grpclog.Infof("addrConn: tryUpdateAddrs curAddr: %v, addrs: %v", ac.curAddr, addrs)
+	if ac.state == connectivity.Shutdown {
+		ac.addrs = addrs
+		return true
+	}
+
+	var curAddrFound bool
+	for _, a := range addrs {
+		if reflect.DeepEqual(ac.curAddr, a) {
+			curAddrFound = true
+			break
+		}
+	}
+	grpclog.Infof("addrConn: tryUpdateAddrs curAddrFound: %v", curAddrFound)
+	if curAddrFound {
+		ac.addrs = addrs
+		ac.addrIdx = 0 // Start reconnecting from beginning in the new list.
+	}
+
+	return curAddrFound
+}
+
+// GetMethodConfig gets the method config of the input method.
+// If there's an exact match for input method (i.e. /service/method), we return
+// the corresponding MethodConfig.
+// If there isn't an exact match for the input method, we look for the default config
+// under the service (i.e /service/). If there is a default MethodConfig for
+// the service, we return it.
+// Otherwise, we return an empty MethodConfig.
+func (cc *ClientConn) GetMethodConfig(method string) MethodConfig {
+	// TODO: Avoid the locking here.
+	cc.mu.RLock()
+	defer cc.mu.RUnlock()
+	m, ok := cc.sc.Methods[method]
+	if !ok {
+		i := strings.LastIndex(method, "/")
+		m = cc.sc.Methods[method[:i+1]]
+	}
+	return m
+}
+
+func (cc *ClientConn) getTransport(ctx context.Context, failfast bool, method string) (transport.ClientTransport, func(balancer.DoneInfo), error) {
+	hdr, _ := metadata.FromOutgoingContext(ctx)
+	t, done, err := cc.blockingpicker.pick(ctx, failfast, balancer.PickOptions{
+		FullMethodName: method,
+		Header:         hdr,
+	})
+	if err != nil {
+		return nil, nil, toRPCErr(err)
+	}
+	return t, done, nil
+}
+
+// handleServiceConfig parses the service config string in JSON format to Go native
+// struct ServiceConfig, and store both the struct and the JSON string in ClientConn.
+func (cc *ClientConn) handleServiceConfig(js string) error {
+	if cc.dopts.disableServiceConfig {
+		return nil
+	}
+	if cc.scRaw == js {
+		return nil
+	}
+	if channelz.IsOn() {
+		channelz.AddTraceEvent(cc.channelzID, &channelz.TraceEventDesc{
+			// The special formatting of \"%s\" instead of %q is to provide nice printing of service config
+			// for human consumption.
+			Desc:     fmt.Sprintf("Channel has a new service config \"%s\"", js),
+			Severity: channelz.CtINFO,
+		})
+	}
+	sc, err := parseServiceConfig(js)
+	if err != nil {
+		return err
+	}
+	cc.mu.Lock()
+	// Check if the ClientConn is already closed. Some fields (e.g.
+	// balancerWrapper) are set to nil when closing the ClientConn, and could
+	// cause nil pointer panic if we don't have this check.
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return nil
+	}
+	cc.scRaw = js
+	cc.sc = sc
+
+	if sc.retryThrottling != nil {
+		newThrottler := &retryThrottler{
+			tokens: sc.retryThrottling.MaxTokens,
+			max:    sc.retryThrottling.MaxTokens,
+			thresh: sc.retryThrottling.MaxTokens / 2,
+			ratio:  sc.retryThrottling.TokenRatio,
+		}
+		cc.retryThrottler.Store(newThrottler)
+	} else {
+		cc.retryThrottler.Store((*retryThrottler)(nil))
+	}
+
+	if sc.LB != nil && *sc.LB != grpclbName { // "grpclb" is not a valid balancer option in service config.
+		if cc.curBalancerName == grpclbName {
+			// If current balancer is grpclb, there's at least one grpclb
+			// balancer address in the resolved list. Don't switch the balancer,
+			// but change the previous balancer name, so if a new resolved
+			// address list doesn't contain grpclb address, balancer will be
+			// switched to *sc.LB.
+			cc.preBalancerName = *sc.LB
+		} else {
+			cc.switchBalancer(*sc.LB)
+			cc.balancerWrapper.handleResolvedAddrs(cc.curAddresses, nil)
+		}
+	}
+
+	cc.mu.Unlock()
+	return nil
+}
+
+func (cc *ClientConn) resolveNow(o resolver.ResolveNowOption) {
+	cc.mu.RLock()
+	r := cc.resolverWrapper
+	cc.mu.RUnlock()
+	if r == nil {
+		return
+	}
+	go r.resolveNow(o)
+}
+
+// ResetConnectBackoff wakes up all subchannels in transient failure and causes
+// them to attempt another connection immediately.  It also resets the backoff
+// times used for subsequent attempts regardless of the current state.
+//
+// In general, this function should not be used.  Typical service or network
+// outages result in a reasonable client reconnection strategy by default.
+// However, if a previously unavailable network becomes available, this may be
+// used to trigger an immediate reconnect.
+//
+// This API is EXPERIMENTAL.
+func (cc *ClientConn) ResetConnectBackoff() {
+	cc.mu.Lock()
+	defer cc.mu.Unlock()
+	for ac := range cc.conns {
+		ac.resetConnectBackoff()
+	}
+}
+
+// Close tears down the ClientConn and all underlying connections.
+func (cc *ClientConn) Close() error {
+	defer cc.cancel()
+
+	cc.mu.Lock()
+	if cc.conns == nil {
+		cc.mu.Unlock()
+		return ErrClientConnClosing
+	}
+	conns := cc.conns
+	cc.conns = nil
+	cc.csMgr.updateState(connectivity.Shutdown)
+
+	rWrapper := cc.resolverWrapper
+	cc.resolverWrapper = nil
+	bWrapper := cc.balancerWrapper
+	cc.balancerWrapper = nil
+	cc.mu.Unlock()
+
+	cc.blockingpicker.close()
+
+	if rWrapper != nil {
+		rWrapper.close()
+	}
+	if bWrapper != nil {
+		bWrapper.close()
+	}
+
+	for ac := range conns {
+		ac.tearDown(ErrClientConnClosing)
+	}
+	if channelz.IsOn() {
+		ted := &channelz.TraceEventDesc{
+			Desc:     "Channel Deleted",
+			Severity: channelz.CtINFO,
+		}
+		if cc.dopts.channelzParentID != 0 {
+			ted.Parent = &channelz.TraceEventDesc{
+				Desc:     fmt.Sprintf("Nested channel(id:%d) deleted", cc.channelzID),
+				Severity: channelz.CtINFO,
+			}
+		}
+		channelz.AddTraceEvent(cc.channelzID, ted)
+		// TraceEvent needs to be called before RemoveEntry, as TraceEvent may add trace reference to
+		// the entity beng deleted, and thus prevent it from being deleted right away.
+		channelz.RemoveEntry(cc.channelzID)
+	}
+	return nil
+}
+
+// addrConn is a network connection to a given address.
+type addrConn struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	cc     *ClientConn
+	dopts  dialOptions
+	acbw   balancer.SubConn
+	scopts balancer.NewSubConnOptions
+
+	transport transport.ClientTransport // The current transport.
+
+	mu      sync.Mutex
+	addrIdx int                // The index in addrs list to start reconnecting from.
+	curAddr resolver.Address   // The current address.
+	addrs   []resolver.Address // All addresses that the resolver resolved to.
+
+	// Use updateConnectivityState for updating addrConn's connectivity state.
+	state connectivity.State
+
+	tearDownErr error // The reason this addrConn is torn down.
+
+	backoffIdx int
+	// backoffDeadline is the time until which resetTransport needs to
+	// wait before increasing backoffIdx count.
+	backoffDeadline time.Time
+	// connectDeadline is the time by which all connection
+	// negotiations must complete.
+	connectDeadline time.Time
+
+	resetBackoff chan struct{}
+
+	channelzID int64 // channelz unique identification number
+	czData     *channelzData
+
+	successfulHandshake bool
+}
+
+// Note: this requires a lock on ac.mu.
+func (ac *addrConn) updateConnectivityState(s connectivity.State) {
+	ac.state = s
+	if channelz.IsOn() {
+		channelz.AddTraceEvent(ac.channelzID, &channelz.TraceEventDesc{
+			Desc:     fmt.Sprintf("Subchannel Connectivity change to %v", s),
+			Severity: channelz.CtINFO,
+		})
+	}
+}
+
+// adjustParams updates parameters used to create transports upon
+// receiving a GoAway.
+func (ac *addrConn) adjustParams(r transport.GoAwayReason) {
+	switch r {
+	case transport.GoAwayTooManyPings:
+		v := 2 * ac.dopts.copts.KeepaliveParams.Time
+		ac.cc.mu.Lock()
+		if v > ac.cc.mkp.Time {
+			ac.cc.mkp.Time = v
+		}
+		ac.cc.mu.Unlock()
+	}
+}
+
+// resetTransport makes sure that a healthy ac.transport exists.
+//
+// The transport will close itself when it encounters an error, or on GOAWAY, or on deadline waiting for handshake, or
+// when the clientconn is closed. Each iteration creating a new transport will try a different address that the balancer
+// assigned to the addrConn, until it has tried all addresses. Once it has tried all addresses, it will re-resolve to
+// get a new address list. If an error is received, the list is re-resolved and the next reset attempt will try from the
+// beginning. This method has backoff built in. The backoff amount starts at 0 and increases each time resolution occurs
+// (addresses are exhausted). The backoff amount is reset to 0 each time a handshake is received.
+//
+// If the DialOption WithWaitForHandshake was set, resetTransport returns successfully only after handshake is received.
+func (ac *addrConn) resetTransport(resolveNow bool) {
+	for {
+		// If this is the first in a line of resets, we want to resolve immediately. The only other time we
+		// want to reset is if we have tried all the addresses handed to us.
+		if resolveNow {
+			ac.mu.Lock()
+			ac.cc.resolveNow(resolver.ResolveNowOption{})
+			ac.mu.Unlock()
+		}
+
+		ac.mu.Lock()
+		if ac.state == connectivity.Shutdown {
+			ac.mu.Unlock()
+			return
+		}
+
+		// If the connection is READY, a failure must have occurred.
+		// Otherwise, we'll consider this is a transient failure when:
+		//   We've exhausted all addresses
+		//   We're in CONNECTING
+		//   And it's not the very first addr to try TODO(deklerk) find a better way to do this than checking ac.successfulHandshake
+		if ac.state == connectivity.Ready || (ac.addrIdx == len(ac.addrs)-1 && ac.state == connectivity.Connecting && !ac.successfulHandshake) {
+			ac.updateConnectivityState(connectivity.TransientFailure)
+			ac.cc.handleSubConnStateChange(ac.acbw, ac.state)
+		}
+		ac.transport = nil
+		ac.mu.Unlock()
+
+		if err := ac.nextAddr(); err != nil {
+			return
+		}
+
+		ac.mu.Lock()
+		if ac.state == connectivity.Shutdown {
+			ac.mu.Unlock()
+			return
+		}
+
+		backoffIdx := ac.backoffIdx
+		backoffFor := ac.dopts.bs.Backoff(backoffIdx)
+
+		// This will be the duration that dial gets to finish.
+		dialDuration := getMinConnectTimeout()
+		if backoffFor > dialDuration {
+			// Give dial more time as we keep failing to connect.
+			dialDuration = backoffFor
+		}
+		start := time.Now()
+		connectDeadline := start.Add(dialDuration)
+		ac.backoffDeadline = start.Add(backoffFor)
+		ac.connectDeadline = connectDeadline
+
+		ac.mu.Unlock()
+
+		ac.cc.mu.RLock()
+		ac.dopts.copts.KeepaliveParams = ac.cc.mkp
+		ac.cc.mu.RUnlock()
+
+		ac.mu.Lock()
+
+		if ac.state == connectivity.Shutdown {
+			ac.mu.Unlock()
+			return
+		}
+
+		if ac.state != connectivity.Connecting {
+			ac.updateConnectivityState(connectivity.Connecting)
+			ac.cc.handleSubConnStateChange(ac.acbw, ac.state)
+		}
+
+		addr := ac.addrs[ac.addrIdx]
+		copts := ac.dopts.copts
+		if ac.scopts.CredsBundle != nil {
+			copts.CredsBundle = ac.scopts.CredsBundle
+		}
+		ac.mu.Unlock()
+
+		if channelz.IsOn() {
+			channelz.AddTraceEvent(ac.channelzID, &channelz.TraceEventDesc{
+				Desc:     fmt.Sprintf("Subchannel picks a new address %q to connect", addr.Addr),
+				Severity: channelz.CtINFO,
+			})
+		}
+
+		if err := ac.createTransport(backoffIdx, addr, copts, connectDeadline); err != nil {
+			continue
+		}
+
+		return
+	}
+}
+
+// createTransport creates a connection to one of the backends in addrs.
+func (ac *addrConn) createTransport(backoffNum int, addr resolver.Address, copts transport.ConnectOptions, connectDeadline time.Time) error {
+	oneReset := sync.Once{}
+	skipReset := make(chan struct{})
+	allowedToReset := make(chan struct{})
+	prefaceReceived := make(chan struct{})
+	onCloseCalled := make(chan struct{})
+
+	var prefaceMu sync.Mutex
+	var serverPrefaceReceived bool
+	var clientPrefaceWrote bool
+
+	onGoAway := func(r transport.GoAwayReason) {
+		ac.mu.Lock()
+		ac.adjustParams(r)
+		ac.mu.Unlock()
+		select {
+		case <-skipReset: // The outer resetTransport loop will handle reconnection.
+			return
+		case <-allowedToReset: // We're in the clear to reset.
+			go oneReset.Do(func() { ac.resetTransport(false) })
+		}
+	}
+
+	prefaceTimer := time.NewTimer(connectDeadline.Sub(time.Now()))
+
+	onClose := func() {
+		close(onCloseCalled)
+		prefaceTimer.Stop()
+
+		select {
+		case <-skipReset: // The outer resetTransport loop will handle reconnection.
+			return
+		case <-allowedToReset: // We're in the clear to reset.
+			oneReset.Do(func() { ac.resetTransport(false) })
+		}
+	}
+
+	target := transport.TargetInfo{
+		Addr:      addr.Addr,
+		Metadata:  addr.Metadata,
+		Authority: ac.cc.authority,
+	}
+
+	onPrefaceReceipt := func() {
+		close(prefaceReceived)
+		prefaceTimer.Stop()
+
+		// TODO(deklerk): optimization; does anyone else actually use this lock? maybe we can just remove it for this scope
+		ac.mu.Lock()
+
+		prefaceMu.Lock()
+		serverPrefaceReceived = true
+		if clientPrefaceWrote {
+			ac.successfulHandshake = true
+			ac.backoffDeadline = time.Time{}
+			ac.connectDeadline = time.Time{}
+			ac.addrIdx = 0
+			ac.backoffIdx = 0
+		}
+		prefaceMu.Unlock()
+
+		ac.mu.Unlock()
+	}
+
+	// Do not cancel in the success path because of this issue in Go1.6: https://github.com/golang/go/issues/15078.
+	connectCtx, cancel := context.WithDeadline(ac.ctx, connectDeadline)
+	if channelz.IsOn() {
+		copts.ChannelzParentID = ac.channelzID
+	}
+
+	newTr, err := transport.NewClientTransport(connectCtx, ac.cc.ctx, target, copts, onPrefaceReceipt, onGoAway, onClose)
+
+	if err == nil {
+		prefaceMu.Lock()
+		clientPrefaceWrote = true
+		if serverPrefaceReceived {
+			ac.successfulHandshake = true
+		}
+		prefaceMu.Unlock()
+
+		if ac.dopts.waitForHandshake {
+			select {
+			case <-prefaceTimer.C:
+				// We didn't get the preface in time.
+				newTr.Close()
+				err = errors.New("timed out waiting for server handshake")
+			case <-prefaceReceived:
+				// We got the preface - huzzah! things are good.
+			case <-onCloseCalled:
+				// The transport has already closed - noop.
+				close(allowedToReset)
+				return nil
+			}
+		} else {
+			go func() {
+				select {
+				case <-prefaceTimer.C:
+					// We didn't get the preface in time.
+					newTr.Close()
+				case <-prefaceReceived:
+					// We got the preface just in the nick of time - huzzah!
+				case <-onCloseCalled:
+					// The transport has already closed - noop.
+				}
+			}()
+		}
+	}
+
+	if err != nil {
+		// newTr is either nil, or closed.
+		cancel()
+		ac.cc.blockingpicker.updateConnectionError(err)
+		ac.mu.Lock()
+		if ac.state == connectivity.Shutdown {
+			// ac.tearDown(...) has been invoked.
+			ac.mu.Unlock()
+
+			// We don't want to reset during this close because we prefer to kick out of this function and let the loop
+			// in resetTransport take care of reconnecting.
+			close(skipReset)
+
+			return errConnClosing
+		}
+		ac.mu.Unlock()
+		grpclog.Warningf("grpc: addrConn.createTransport failed to connect to %v. Err :%v. Reconnecting...", addr, err)
+
+		// We don't want to reset during this close because we prefer to kick out of this function and let the loop
+		// in resetTransport take care of reconnecting.
+		close(skipReset)
+
+		return err
+	}
+
+	ac.mu.Lock()
+
+	if ac.state == connectivity.Shutdown {
+		ac.mu.Unlock()
+
+		// We don't want to reset during this close because we prefer to kick out of this function and let the loop
+		// in resetTransport take care of reconnecting.
+		close(skipReset)
+
+		newTr.Close()
+		return errConnClosing
+	}
+
+	ac.updateConnectivityState(connectivity.Ready)
+	ac.cc.handleSubConnStateChange(ac.acbw, ac.state)
+	ac.transport = newTr
+	ac.curAddr = addr
+
+	ac.mu.Unlock()
+
+	// Ok, _now_ we will finally let the transport reset if it encounters a closable error. Without this, the reader
+	// goroutine failing races with all the code in this method that sets the connection to "ready".
+	close(allowedToReset)
+	return nil
+}
+
+// nextAddr increments the addrIdx if there are more addresses to try. If
+// there are no more addrs to try it will re-resolve, set addrIdx to 0, and
+// increment the backoffIdx.
+//
+// nextAddr must be called without ac.mu being held.
+func (ac *addrConn) nextAddr() error {
+	ac.mu.Lock()
+
+	// If a handshake has been observed, we expect the counters to have manually
+	// been reset so we'll just return, since we want the next usage to start
+	// at index 0.
+	if ac.successfulHandshake {
+		ac.successfulHandshake = false
+		ac.mu.Unlock()
+		return nil
+	}
+
+	if ac.addrIdx < len(ac.addrs)-1 {
+		ac.addrIdx++
+		ac.mu.Unlock()
+		return nil
+	}
+
+	ac.addrIdx = 0
+	ac.backoffIdx++
+
+	if ac.state == connectivity.Shutdown {
+		ac.mu.Unlock()
+		return errConnClosing
+	}
+	ac.cc.resolveNow(resolver.ResolveNowOption{})
+	backoffDeadline := ac.backoffDeadline
+	b := ac.resetBackoff
+	ac.mu.Unlock()
+	timer := time.NewTimer(backoffDeadline.Sub(time.Now()))
+	select {
+	case <-timer.C:
+	case <-b:
+		timer.Stop()
+	case <-ac.ctx.Done():
+		timer.Stop()
+		return ac.ctx.Err()
+	}
+	return nil
+}
+
+func (ac *addrConn) resetConnectBackoff() {
+	ac.mu.Lock()
+	close(ac.resetBackoff)
+	ac.backoffIdx = 0
+	ac.resetBackoff = make(chan struct{})
+	ac.mu.Unlock()
+}
+
+// getReadyTransport returns the transport if ac's state is READY.
+// Otherwise it returns nil, false.
+// If ac's state is IDLE, it will trigger ac to connect.
+func (ac *addrConn) getReadyTransport() (transport.ClientTransport, bool) {
+	ac.mu.Lock()
+	if ac.state == connectivity.Ready && ac.transport != nil {
+		t := ac.transport
+		ac.mu.Unlock()
+		return t, true
+	}
+	var idle bool
+	if ac.state == connectivity.Idle {
+		idle = true
+	}
+	ac.mu.Unlock()
+	// Trigger idle ac to connect.
+	if idle {
+		ac.connect()
+	}
+	return nil, false
+}
+
+// tearDown starts to tear down the addrConn.
+// TODO(zhaoq): Make this synchronous to avoid unbounded memory consumption in
+// some edge cases (e.g., the caller opens and closes many addrConn's in a
+// tight loop.
+// tearDown doesn't remove ac from ac.cc.conns.
+func (ac *addrConn) tearDown(err error) {
+	ac.mu.Lock()
+	if ac.state == connectivity.Shutdown {
+		ac.mu.Unlock()
+		return
+	}
+	// We have to set the state to Shutdown before anything else to prevent races
+	// between setting the state and logic that waits on context cancelation / etc.
+	ac.updateConnectivityState(connectivity.Shutdown)
+	ac.cancel()
+	ac.tearDownErr = err
+	ac.cc.handleSubConnStateChange(ac.acbw, ac.state)
+	ac.curAddr = resolver.Address{}
+	if err == errConnDrain && ac.transport != nil {
+		// GracefulClose(...) may be executed multiple times when
+		// i) receiving multiple GoAway frames from the server; or
+		// ii) there are concurrent name resolver/Balancer triggered
+		// address removal and GoAway.
+		// We have to unlock and re-lock here because GracefulClose => Close => onClose, which requires locking ac.mu.
+		ac.mu.Unlock()
+		ac.transport.GracefulClose()
+		ac.mu.Lock()
+	}
+	if channelz.IsOn() {
+		channelz.AddTraceEvent(ac.channelzID, &channelz.TraceEventDesc{
+			Desc:     "Subchannel Deleted",
+			Severity: channelz.CtINFO,
+			Parent: &channelz.TraceEventDesc{
+				Desc:     fmt.Sprintf("Subchanel(id:%d) deleted", ac.channelzID),
+				Severity: channelz.CtINFO,
+			},
+		})
+		// TraceEvent needs to be called before RemoveEntry, as TraceEvent may add trace reference to
+		// the entity beng deleted, and thus prevent it from being deleted right away.
+		channelz.RemoveEntry(ac.channelzID)
+	}
+	ac.mu.Unlock()
+}
+
+func (ac *addrConn) getState() connectivity.State {
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	return ac.state
+}
+
+func (ac *addrConn) ChannelzMetric() *channelz.ChannelInternalMetric {
+	ac.mu.Lock()
+	addr := ac.curAddr.Addr
+	ac.mu.Unlock()
+	return &channelz.ChannelInternalMetric{
+		State:                    ac.getState(),
+		Target:                   addr,
+		CallsStarted:             atomic.LoadInt64(&ac.czData.callsStarted),
+		CallsSucceeded:           atomic.LoadInt64(&ac.czData.callsSucceeded),
+		CallsFailed:              atomic.LoadInt64(&ac.czData.callsFailed),
+		LastCallStartedTimestamp: time.Unix(0, atomic.LoadInt64(&ac.czData.lastCallStartedTime)),
+	}
+}
+
+func (ac *addrConn) incrCallsStarted() {
+	atomic.AddInt64(&ac.czData.callsStarted, 1)
+	atomic.StoreInt64(&ac.czData.lastCallStartedTime, time.Now().UnixNano())
+}
+
+func (ac *addrConn) incrCallsSucceeded() {
+	atomic.AddInt64(&ac.czData.callsSucceeded, 1)
+}
+
+func (ac *addrConn) incrCallsFailed() {
+	atomic.AddInt64(&ac.czData.callsFailed, 1)
+}
+
+type retryThrottler struct {
+	max    float64
+	thresh float64
+	ratio  float64
+
+	mu     sync.Mutex
+	tokens float64 // TODO(dfawley): replace with atomic and remove lock.
+}
+
+// throttle subtracts a retry token from the pool and returns whether a retry
+// should be throttled (disallowed) based upon the retry throttling policy in
+// the service config.
+func (rt *retryThrottler) throttle() bool {
+	if rt == nil {
+		return false
+	}
+	rt.mu.Lock()
+	defer rt.mu.Unlock()
+	rt.tokens--
+	if rt.tokens < 0 {
+		rt.tokens = 0
+	}
+	return rt.tokens <= rt.thresh
+}
+
+func (rt *retryThrottler) successfulRPC() {
+	if rt == nil {
+		return
+	}
+	rt.mu.Lock()
+	defer rt.mu.Unlock()
+	rt.tokens += rt.ratio
+	if rt.tokens > rt.max {
+		rt.tokens = rt.max
+	}
+}
+
+type channelzChannel struct {
+	cc *ClientConn
+}
+
+func (c *channelzChannel) ChannelzMetric() *channelz.ChannelInternalMetric {
+	return c.cc.channelzMetric()
+}
+
+// ErrClientConnTimeout indicates that the ClientConn cannot establish the
+// underlying connections within the specified timeout.
+//
+// Deprecated: This error is never returned by grpc and should not be
+// referenced by users.
+var ErrClientConnTimeout = errors.New("grpc: timed out when dialing")
diff --git a/go/vendor/google.golang.org/grpc/codec.go b/go/vendor/google.golang.org/grpc/codec.go
new file mode 100644
index 0000000..1297765
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/codec.go
@@ -0,0 +1,50 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"google.golang.org/grpc/encoding"
+	_ "google.golang.org/grpc/encoding/proto" // to register the Codec for "proto"
+)
+
+// baseCodec contains the functionality of both Codec and encoding.Codec, but
+// omits the name/string, which vary between the two and are not needed for
+// anything besides the registry in the encoding package.
+type baseCodec interface {
+	Marshal(v interface{}) ([]byte, error)
+	Unmarshal(data []byte, v interface{}) error
+}
+
+var _ baseCodec = Codec(nil)
+var _ baseCodec = encoding.Codec(nil)
+
+// Codec defines the interface gRPC uses to encode and decode messages.
+// Note that implementations of this interface must be thread safe;
+// a Codec's methods can be called from concurrent goroutines.
+//
+// Deprecated: use encoding.Codec instead.
+type Codec interface {
+	// Marshal returns the wire format of v.
+	Marshal(v interface{}) ([]byte, error)
+	// Unmarshal parses the wire format into v.
+	Unmarshal(data []byte, v interface{}) error
+	// String returns the name of the Codec implementation.  This is unused by
+	// gRPC.
+	String() string
+}
diff --git a/go/vendor/google.golang.org/grpc/codegen.sh b/go/vendor/google.golang.org/grpc/codegen.sh
new file mode 100755
index 0000000..4cdc6ba
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/codegen.sh
@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+# This script serves as an example to demonstrate how to generate the gRPC-Go
+# interface and the related messages from .proto file.
+#
+# It assumes the installation of i) Google proto buffer compiler at
+# https://github.com/google/protobuf (after v2.6.1) and ii) the Go codegen
+# plugin at https://github.com/golang/protobuf (after 2015-02-20). If you have
+# not, please install them first.
+#
+# We recommend running this script at $GOPATH/src.
+#
+# If this is not what you need, feel free to make your own scripts. Again, this
+# script is for demonstration purpose.
+#
+proto=$1
+protoc --go_out=plugins=grpc:. $proto
diff --git a/go/vendor/google.golang.org/grpc/codes/code_string.go b/go/vendor/google.golang.org/grpc/codes/code_string.go
new file mode 100644
index 0000000..0b206a5
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/codes/code_string.go
@@ -0,0 +1,62 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package codes
+
+import "strconv"
+
+func (c Code) String() string {
+	switch c {
+	case OK:
+		return "OK"
+	case Canceled:
+		return "Canceled"
+	case Unknown:
+		return "Unknown"
+	case InvalidArgument:
+		return "InvalidArgument"
+	case DeadlineExceeded:
+		return "DeadlineExceeded"
+	case NotFound:
+		return "NotFound"
+	case AlreadyExists:
+		return "AlreadyExists"
+	case PermissionDenied:
+		return "PermissionDenied"
+	case ResourceExhausted:
+		return "ResourceExhausted"
+	case FailedPrecondition:
+		return "FailedPrecondition"
+	case Aborted:
+		return "Aborted"
+	case OutOfRange:
+		return "OutOfRange"
+	case Unimplemented:
+		return "Unimplemented"
+	case Internal:
+		return "Internal"
+	case Unavailable:
+		return "Unavailable"
+	case DataLoss:
+		return "DataLoss"
+	case Unauthenticated:
+		return "Unauthenticated"
+	default:
+		return "Code(" + strconv.FormatInt(int64(c), 10) + ")"
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/codes/codes.go b/go/vendor/google.golang.org/grpc/codes/codes.go
new file mode 100644
index 0000000..d9b9d57
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/codes/codes.go
@@ -0,0 +1,197 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package codes defines the canonical error codes used by gRPC. It is
+// consistent across various languages.
+package codes // import "google.golang.org/grpc/codes"
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// A Code is an unsigned 32-bit error code as defined in the gRPC spec.
+type Code uint32
+
+const (
+	// OK is returned on success.
+	OK Code = 0
+
+	// Canceled indicates the operation was canceled (typically by the caller).
+	Canceled Code = 1
+
+	// Unknown error. An example of where this error may be returned is
+	// if a Status value received from another address space belongs to
+	// an error-space that is not known in this address space. Also
+	// errors raised by APIs that do not return enough error information
+	// may be converted to this error.
+	Unknown Code = 2
+
+	// InvalidArgument indicates client specified an invalid argument.
+	// Note that this differs from FailedPrecondition. It indicates arguments
+	// that are problematic regardless of the state of the system
+	// (e.g., a malformed file name).
+	InvalidArgument Code = 3
+
+	// DeadlineExceeded means operation expired before completion.
+	// For operations that change the state of the system, this error may be
+	// returned even if the operation has completed successfully. For
+	// example, a successful response from a server could have been delayed
+	// long enough for the deadline to expire.
+	DeadlineExceeded Code = 4
+
+	// NotFound means some requested entity (e.g., file or directory) was
+	// not found.
+	NotFound Code = 5
+
+	// AlreadyExists means an attempt to create an entity failed because one
+	// already exists.
+	AlreadyExists Code = 6
+
+	// PermissionDenied indicates the caller does not have permission to
+	// execute the specified operation. It must not be used for rejections
+	// caused by exhausting some resource (use ResourceExhausted
+	// instead for those errors). It must not be
+	// used if the caller cannot be identified (use Unauthenticated
+	// instead for those errors).
+	PermissionDenied Code = 7
+
+	// ResourceExhausted indicates some resource has been exhausted, perhaps
+	// a per-user quota, or perhaps the entire file system is out of space.
+	ResourceExhausted Code = 8
+
+	// FailedPrecondition indicates operation was rejected because the
+	// system is not in a state required for the operation's execution.
+	// For example, directory to be deleted may be non-empty, an rmdir
+	// operation is applied to a non-directory, etc.
+	//
+	// A litmus test that may help a service implementor in deciding
+	// between FailedPrecondition, Aborted, and Unavailable:
+	//  (a) Use Unavailable if the client can retry just the failing call.
+	//  (b) Use Aborted if the client should retry at a higher-level
+	//      (e.g., restarting a read-modify-write sequence).
+	//  (c) Use FailedPrecondition if the client should not retry until
+	//      the system state has been explicitly fixed. E.g., if an "rmdir"
+	//      fails because the directory is non-empty, FailedPrecondition
+	//      should be returned since the client should not retry unless
+	//      they have first fixed up the directory by deleting files from it.
+	//  (d) Use FailedPrecondition if the client performs conditional
+	//      REST Get/Update/Delete on a resource and the resource on the
+	//      server does not match the condition. E.g., conflicting
+	//      read-modify-write on the same resource.
+	FailedPrecondition Code = 9
+
+	// Aborted indicates the operation was aborted, typically due to a
+	// concurrency issue like sequencer check failures, transaction aborts,
+	// etc.
+	//
+	// See litmus test above for deciding between FailedPrecondition,
+	// Aborted, and Unavailable.
+	Aborted Code = 10
+
+	// OutOfRange means operation was attempted past the valid range.
+	// E.g., seeking or reading past end of file.
+	//
+	// Unlike InvalidArgument, this error indicates a problem that may
+	// be fixed if the system state changes. For example, a 32-bit file
+	// system will generate InvalidArgument if asked to read at an
+	// offset that is not in the range [0,2^32-1], but it will generate
+	// OutOfRange if asked to read from an offset past the current
+	// file size.
+	//
+	// There is a fair bit of overlap between FailedPrecondition and
+	// OutOfRange. We recommend using OutOfRange (the more specific
+	// error) when it applies so that callers who are iterating through
+	// a space can easily look for an OutOfRange error to detect when
+	// they are done.
+	OutOfRange Code = 11
+
+	// Unimplemented indicates operation is not implemented or not
+	// supported/enabled in this service.
+	Unimplemented Code = 12
+
+	// Internal errors. Means some invariants expected by underlying
+	// system has been broken. If you see one of these errors,
+	// something is very broken.
+	Internal Code = 13
+
+	// Unavailable indicates the service is currently unavailable.
+	// This is a most likely a transient condition and may be corrected
+	// by retrying with a backoff.
+	//
+	// See litmus test above for deciding between FailedPrecondition,
+	// Aborted, and Unavailable.
+	Unavailable Code = 14
+
+	// DataLoss indicates unrecoverable data loss or corruption.
+	DataLoss Code = 15
+
+	// Unauthenticated indicates the request does not have valid
+	// authentication credentials for the operation.
+	Unauthenticated Code = 16
+
+	_maxCode = 17
+)
+
+var strToCode = map[string]Code{
+	`"OK"`: OK,
+	`"CANCELLED"`:/* [sic] */ Canceled,
+	`"UNKNOWN"`:             Unknown,
+	`"INVALID_ARGUMENT"`:    InvalidArgument,
+	`"DEADLINE_EXCEEDED"`:   DeadlineExceeded,
+	`"NOT_FOUND"`:           NotFound,
+	`"ALREADY_EXISTS"`:      AlreadyExists,
+	`"PERMISSION_DENIED"`:   PermissionDenied,
+	`"RESOURCE_EXHAUSTED"`:  ResourceExhausted,
+	`"FAILED_PRECONDITION"`: FailedPrecondition,
+	`"ABORTED"`:             Aborted,
+	`"OUT_OF_RANGE"`:        OutOfRange,
+	`"UNIMPLEMENTED"`:       Unimplemented,
+	`"INTERNAL"`:            Internal,
+	`"UNAVAILABLE"`:         Unavailable,
+	`"DATA_LOSS"`:           DataLoss,
+	`"UNAUTHENTICATED"`:     Unauthenticated,
+}
+
+// UnmarshalJSON unmarshals b into the Code.
+func (c *Code) UnmarshalJSON(b []byte) error {
+	// From json.Unmarshaler: By convention, to approximate the behavior of
+	// Unmarshal itself, Unmarshalers implement UnmarshalJSON([]byte("null")) as
+	// a no-op.
+	if string(b) == "null" {
+		return nil
+	}
+	if c == nil {
+		return fmt.Errorf("nil receiver passed to UnmarshalJSON")
+	}
+
+	if ci, err := strconv.ParseUint(string(b), 10, 32); err == nil {
+		if ci >= _maxCode {
+			return fmt.Errorf("invalid code: %q", ci)
+		}
+
+		*c = Code(ci)
+		return nil
+	}
+
+	if jc, ok := strToCode[string(b)]; ok {
+		*c = jc
+		return nil
+	}
+	return fmt.Errorf("invalid code: %q", string(b))
+}
diff --git a/go/vendor/google.golang.org/grpc/connectivity/connectivity.go b/go/vendor/google.golang.org/grpc/connectivity/connectivity.go
new file mode 100644
index 0000000..568ef5d
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/connectivity/connectivity.go
@@ -0,0 +1,72 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package connectivity defines connectivity semantics.
+// For details, see https://github.com/grpc/grpc/blob/master/doc/connectivity-semantics-and-api.md.
+// All APIs in this package are experimental.
+package connectivity
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/grpclog"
+)
+
+// State indicates the state of connectivity.
+// It can be the state of a ClientConn or SubConn.
+type State int
+
+func (s State) String() string {
+	switch s {
+	case Idle:
+		return "IDLE"
+	case Connecting:
+		return "CONNECTING"
+	case Ready:
+		return "READY"
+	case TransientFailure:
+		return "TRANSIENT_FAILURE"
+	case Shutdown:
+		return "SHUTDOWN"
+	default:
+		grpclog.Errorf("unknown connectivity state: %d", s)
+		return "Invalid-State"
+	}
+}
+
+const (
+	// Idle indicates the ClientConn is idle.
+	Idle State = iota
+	// Connecting indicates the ClienConn is connecting.
+	Connecting
+	// Ready indicates the ClientConn is ready for work.
+	Ready
+	// TransientFailure indicates the ClientConn has seen a failure but expects to recover.
+	TransientFailure
+	// Shutdown indicates the ClientConn has started shutting down.
+	Shutdown
+)
+
+// Reporter reports the connectivity states.
+type Reporter interface {
+	// CurrentState returns the current state of the reporter.
+	CurrentState() State
+	// WaitForStateChange blocks until the reporter's state is different from the given state,
+	// and returns true.
+	// It returns false if <-ctx.Done() can proceed (ctx got timeout or got canceled).
+	WaitForStateChange(context.Context, State) bool
+}
diff --git a/go/vendor/google.golang.org/grpc/credentials/credentials.go b/go/vendor/google.golang.org/grpc/credentials/credentials.go
new file mode 100644
index 0000000..6c2b811
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/credentials/credentials.go
@@ -0,0 +1,312 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package credentials implements various credentials supported by gRPC library,
+// which encapsulate all the state needed by a client to authenticate with a
+// server and make various assertions, e.g., about the client's identity, role,
+// or whether it is authorized to make a particular call.
+package credentials // import "google.golang.org/grpc/credentials"
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"strings"
+
+	"github.com/golang/protobuf/proto"
+	"golang.org/x/net/context"
+)
+
+// alpnProtoStr are the specified application level protocols for gRPC.
+var alpnProtoStr = []string{"h2"}
+
+// PerRPCCredentials defines the common interface for the credentials which need to
+// attach security information to every RPC (e.g., oauth2).
+type PerRPCCredentials interface {
+	// GetRequestMetadata gets the current request metadata, refreshing
+	// tokens if required. This should be called by the transport layer on
+	// each request, and the data should be populated in headers or other
+	// context. If a status code is returned, it will be used as the status
+	// for the RPC. uri is the URI of the entry point for the request.
+	// When supported by the underlying implementation, ctx can be used for
+	// timeout and cancellation.
+	// TODO(zhaoq): Define the set of the qualified keys instead of leaving
+	// it as an arbitrary string.
+	GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error)
+	// RequireTransportSecurity indicates whether the credentials requires
+	// transport security.
+	RequireTransportSecurity() bool
+}
+
+// ProtocolInfo provides information regarding the gRPC wire protocol version,
+// security protocol, security protocol version in use, server name, etc.
+type ProtocolInfo struct {
+	// ProtocolVersion is the gRPC wire protocol version.
+	ProtocolVersion string
+	// SecurityProtocol is the security protocol in use.
+	SecurityProtocol string
+	// SecurityVersion is the security protocol version.
+	SecurityVersion string
+	// ServerName is the user-configured server name.
+	ServerName string
+}
+
+// AuthInfo defines the common interface for the auth information the users are interested in.
+type AuthInfo interface {
+	AuthType() string
+}
+
+// ErrConnDispatched indicates that rawConn has been dispatched out of gRPC
+// and the caller should not close rawConn.
+var ErrConnDispatched = errors.New("credentials: rawConn is dispatched out of gRPC")
+
+// TransportCredentials defines the common interface for all the live gRPC wire
+// protocols and supported transport security protocols (e.g., TLS, SSL).
+type TransportCredentials interface {
+	// ClientHandshake does the authentication handshake specified by the corresponding
+	// authentication protocol on rawConn for clients. It returns the authenticated
+	// connection and the corresponding auth information about the connection.
+	// Implementations must use the provided context to implement timely cancellation.
+	// gRPC will try to reconnect if the error returned is a temporary error
+	// (io.EOF, context.DeadlineExceeded or err.Temporary() == true).
+	// If the returned error is a wrapper error, implementations should make sure that
+	// the error implements Temporary() to have the correct retry behaviors.
+	//
+	// If the returned net.Conn is closed, it MUST close the net.Conn provided.
+	ClientHandshake(context.Context, string, net.Conn) (net.Conn, AuthInfo, error)
+	// ServerHandshake does the authentication handshake for servers. It returns
+	// the authenticated connection and the corresponding auth information about
+	// the connection.
+	//
+	// If the returned net.Conn is closed, it MUST close the net.Conn provided.
+	ServerHandshake(net.Conn) (net.Conn, AuthInfo, error)
+	// Info provides the ProtocolInfo of this TransportCredentials.
+	Info() ProtocolInfo
+	// Clone makes a copy of this TransportCredentials.
+	Clone() TransportCredentials
+	// OverrideServerName overrides the server name used to verify the hostname on the returned certificates from the server.
+	// gRPC internals also use it to override the virtual hosting name if it is set.
+	// It must be called before dialing. Currently, this is only used by grpclb.
+	OverrideServerName(string) error
+}
+
+// Bundle is a combination of TransportCredentials and PerRPCCredentials.
+//
+// It also contains a mode switching method, so it can be used as a combination
+// of different credential policies.
+//
+// Bundle cannot be used together with individual TransportCredentials.
+// PerRPCCredentials from Bundle will be appended to other PerRPCCredentials.
+//
+// This API is experimental.
+type Bundle interface {
+	TransportCredentials() TransportCredentials
+	PerRPCCredentials() PerRPCCredentials
+	// NewWithMode should make a copy of Bundle, and switch mode. Modifying the
+	// existing Bundle may cause races.
+	//
+	// NewWithMode returns nil if the requested mode is not supported.
+	NewWithMode(mode string) (Bundle, error)
+}
+
+// TLSInfo contains the auth information for a TLS authenticated connection.
+// It implements the AuthInfo interface.
+type TLSInfo struct {
+	State tls.ConnectionState
+}
+
+// AuthType returns the type of TLSInfo as a string.
+func (t TLSInfo) AuthType() string {
+	return "tls"
+}
+
+// GetChannelzSecurityValue returns security info requested by channelz.
+func (t TLSInfo) GetChannelzSecurityValue() ChannelzSecurityValue {
+	v := &TLSChannelzSecurityValue{
+		StandardName: cipherSuiteLookup[t.State.CipherSuite],
+	}
+	// Currently there's no way to get LocalCertificate info from tls package.
+	if len(t.State.PeerCertificates) > 0 {
+		v.RemoteCertificate = t.State.PeerCertificates[0].Raw
+	}
+	return v
+}
+
+// tlsCreds is the credentials required for authenticating a connection using TLS.
+type tlsCreds struct {
+	// TLS configuration
+	config *tls.Config
+}
+
+func (c tlsCreds) Info() ProtocolInfo {
+	return ProtocolInfo{
+		SecurityProtocol: "tls",
+		SecurityVersion:  "1.2",
+		ServerName:       c.config.ServerName,
+	}
+}
+
+func (c *tlsCreds) ClientHandshake(ctx context.Context, authority string, rawConn net.Conn) (_ net.Conn, _ AuthInfo, err error) {
+	// use local cfg to avoid clobbering ServerName if using multiple endpoints
+	cfg := cloneTLSConfig(c.config)
+	if cfg.ServerName == "" {
+		colonPos := strings.LastIndex(authority, ":")
+		if colonPos == -1 {
+			colonPos = len(authority)
+		}
+		cfg.ServerName = authority[:colonPos]
+	}
+	conn := tls.Client(rawConn, cfg)
+	errChannel := make(chan error, 1)
+	go func() {
+		errChannel <- conn.Handshake()
+	}()
+	select {
+	case err := <-errChannel:
+		if err != nil {
+			return nil, nil, err
+		}
+	case <-ctx.Done():
+		return nil, nil, ctx.Err()
+	}
+	return tlsConn{Conn: conn, rawConn: rawConn}, TLSInfo{conn.ConnectionState()}, nil
+}
+
+func (c *tlsCreds) ServerHandshake(rawConn net.Conn) (net.Conn, AuthInfo, error) {
+	conn := tls.Server(rawConn, c.config)
+	if err := conn.Handshake(); err != nil {
+		return nil, nil, err
+	}
+	return tlsConn{Conn: conn, rawConn: rawConn}, TLSInfo{conn.ConnectionState()}, nil
+}
+
+func (c *tlsCreds) Clone() TransportCredentials {
+	return NewTLS(c.config)
+}
+
+func (c *tlsCreds) OverrideServerName(serverNameOverride string) error {
+	c.config.ServerName = serverNameOverride
+	return nil
+}
+
+// NewTLS uses c to construct a TransportCredentials based on TLS.
+func NewTLS(c *tls.Config) TransportCredentials {
+	tc := &tlsCreds{cloneTLSConfig(c)}
+	tc.config.NextProtos = alpnProtoStr
+	return tc
+}
+
+// NewClientTLSFromCert constructs TLS credentials from the input certificate for client.
+// serverNameOverride is for testing only. If set to a non empty string,
+// it will override the virtual host name of authority (e.g. :authority header field) in requests.
+func NewClientTLSFromCert(cp *x509.CertPool, serverNameOverride string) TransportCredentials {
+	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp})
+}
+
+// NewClientTLSFromFile constructs TLS credentials from the input certificate file for client.
+// serverNameOverride is for testing only. If set to a non empty string,
+// it will override the virtual host name of authority (e.g. :authority header field) in requests.
+func NewClientTLSFromFile(certFile, serverNameOverride string) (TransportCredentials, error) {
+	b, err := ioutil.ReadFile(certFile)
+	if err != nil {
+		return nil, err
+	}
+	cp := x509.NewCertPool()
+	if !cp.AppendCertsFromPEM(b) {
+		return nil, fmt.Errorf("credentials: failed to append certificates")
+	}
+	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp}), nil
+}
+
+// NewServerTLSFromCert constructs TLS credentials from the input certificate for server.
+func NewServerTLSFromCert(cert *tls.Certificate) TransportCredentials {
+	return NewTLS(&tls.Config{Certificates: []tls.Certificate{*cert}})
+}
+
+// NewServerTLSFromFile constructs TLS credentials from the input certificate file and key
+// file for server.
+func NewServerTLSFromFile(certFile, keyFile string) (TransportCredentials, error) {
+	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
+	if err != nil {
+		return nil, err
+	}
+	return NewTLS(&tls.Config{Certificates: []tls.Certificate{cert}}), nil
+}
+
+// ChannelzSecurityInfo defines the interface that security protocols should implement
+// in order to provide security info to channelz.
+type ChannelzSecurityInfo interface {
+	GetSecurityValue() ChannelzSecurityValue
+}
+
+// ChannelzSecurityValue defines the interface that GetSecurityValue() return value
+// should satisfy. This interface should only be satisfied by *TLSChannelzSecurityValue
+// and *OtherChannelzSecurityValue.
+type ChannelzSecurityValue interface {
+	isChannelzSecurityValue()
+}
+
+// TLSChannelzSecurityValue defines the struct that TLS protocol should return
+// from GetSecurityValue(), containing security info like cipher and certificate used.
+type TLSChannelzSecurityValue struct {
+	StandardName      string
+	LocalCertificate  []byte
+	RemoteCertificate []byte
+}
+
+func (*TLSChannelzSecurityValue) isChannelzSecurityValue() {}
+
+// OtherChannelzSecurityValue defines the struct that non-TLS protocol should return
+// from GetSecurityValue(), which contains protocol specific security info. Note
+// the Value field will be sent to users of channelz requesting channel info, and
+// thus sensitive info should better be avoided.
+type OtherChannelzSecurityValue struct {
+	Name  string
+	Value proto.Message
+}
+
+func (*OtherChannelzSecurityValue) isChannelzSecurityValue() {}
+
+type tlsConn struct {
+	*tls.Conn
+	rawConn net.Conn
+}
+
+var cipherSuiteLookup = map[uint16]string{
+	tls.TLS_RSA_WITH_RC4_128_SHA:                "TLS_RSA_WITH_RC4_128_SHA",
+	tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA:           "TLS_RSA_WITH_3DES_EDE_CBC_SHA",
+	tls.TLS_RSA_WITH_AES_128_CBC_SHA:            "TLS_RSA_WITH_AES_128_CBC_SHA",
+	tls.TLS_RSA_WITH_AES_256_CBC_SHA:            "TLS_RSA_WITH_AES_256_CBC_SHA",
+	tls.TLS_RSA_WITH_AES_128_GCM_SHA256:         "TLS_RSA_WITH_AES_128_GCM_SHA256",
+	tls.TLS_RSA_WITH_AES_256_GCM_SHA384:         "TLS_RSA_WITH_AES_256_GCM_SHA384",
+	tls.TLS_ECDHE_ECDSA_WITH_RC4_128_SHA:        "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA:    "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA:    "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA:          "TLS_ECDHE_RSA_WITH_RC4_128_SHA",
+	tls.TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA:     "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA:      "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA:      "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:   "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
+	tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384:   "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384: "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
+	tls.TLS_FALLBACK_SCSV:                       "TLS_FALLBACK_SCSV",
+}
diff --git a/go/vendor/google.golang.org/grpc/credentials/go16.go b/go/vendor/google.golang.org/grpc/credentials/go16.go
new file mode 100644
index 0000000..d6bbcc9
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/credentials/go16.go
@@ -0,0 +1,57 @@
+// +build !go1.7
+
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package credentials
+
+import (
+	"crypto/tls"
+)
+
+// cloneTLSConfig returns a shallow clone of the exported
+// fields of cfg, ignoring the unexported sync.Once, which
+// contains a mutex and must not be copied.
+//
+// If cfg is nil, a new zero tls.Config is returned.
+func cloneTLSConfig(cfg *tls.Config) *tls.Config {
+	if cfg == nil {
+		return &tls.Config{}
+	}
+	return &tls.Config{
+		Rand:                     cfg.Rand,
+		Time:                     cfg.Time,
+		Certificates:             cfg.Certificates,
+		NameToCertificate:        cfg.NameToCertificate,
+		GetCertificate:           cfg.GetCertificate,
+		RootCAs:                  cfg.RootCAs,
+		NextProtos:               cfg.NextProtos,
+		ServerName:               cfg.ServerName,
+		ClientAuth:               cfg.ClientAuth,
+		ClientCAs:                cfg.ClientCAs,
+		InsecureSkipVerify:       cfg.InsecureSkipVerify,
+		CipherSuites:             cfg.CipherSuites,
+		PreferServerCipherSuites: cfg.PreferServerCipherSuites,
+		SessionTicketsDisabled:   cfg.SessionTicketsDisabled,
+		SessionTicketKey:         cfg.SessionTicketKey,
+		ClientSessionCache:       cfg.ClientSessionCache,
+		MinVersion:               cfg.MinVersion,
+		MaxVersion:               cfg.MaxVersion,
+		CurvePreferences:         cfg.CurvePreferences,
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/credentials/go17.go b/go/vendor/google.golang.org/grpc/credentials/go17.go
new file mode 100644
index 0000000..fbd5000
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/credentials/go17.go
@@ -0,0 +1,59 @@
+// +build go1.7,!go1.8
+
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package credentials
+
+import (
+	"crypto/tls"
+)
+
+// cloneTLSConfig returns a shallow clone of the exported
+// fields of cfg, ignoring the unexported sync.Once, which
+// contains a mutex and must not be copied.
+//
+// If cfg is nil, a new zero tls.Config is returned.
+func cloneTLSConfig(cfg *tls.Config) *tls.Config {
+	if cfg == nil {
+		return &tls.Config{}
+	}
+	return &tls.Config{
+		Rand:                        cfg.Rand,
+		Time:                        cfg.Time,
+		Certificates:                cfg.Certificates,
+		NameToCertificate:           cfg.NameToCertificate,
+		GetCertificate:              cfg.GetCertificate,
+		RootCAs:                     cfg.RootCAs,
+		NextProtos:                  cfg.NextProtos,
+		ServerName:                  cfg.ServerName,
+		ClientAuth:                  cfg.ClientAuth,
+		ClientCAs:                   cfg.ClientCAs,
+		InsecureSkipVerify:          cfg.InsecureSkipVerify,
+		CipherSuites:                cfg.CipherSuites,
+		PreferServerCipherSuites:    cfg.PreferServerCipherSuites,
+		SessionTicketsDisabled:      cfg.SessionTicketsDisabled,
+		SessionTicketKey:            cfg.SessionTicketKey,
+		ClientSessionCache:          cfg.ClientSessionCache,
+		MinVersion:                  cfg.MinVersion,
+		MaxVersion:                  cfg.MaxVersion,
+		CurvePreferences:            cfg.CurvePreferences,
+		DynamicRecordSizingDisabled: cfg.DynamicRecordSizingDisabled,
+		Renegotiation:               cfg.Renegotiation,
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/credentials/go18.go b/go/vendor/google.golang.org/grpc/credentials/go18.go
new file mode 100644
index 0000000..db30d46
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/credentials/go18.go
@@ -0,0 +1,46 @@
+// +build go1.8
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package credentials
+
+import (
+	"crypto/tls"
+)
+
+func init() {
+	cipherSuiteLookup[tls.TLS_RSA_WITH_AES_128_CBC_SHA256] = "TLS_RSA_WITH_AES_128_CBC_SHA256"
+	cipherSuiteLookup[tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256] = "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256"
+	cipherSuiteLookup[tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256] = "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256"
+	cipherSuiteLookup[tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305] = "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305"
+	cipherSuiteLookup[tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305] = "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305"
+}
+
+// cloneTLSConfig returns a shallow clone of the exported
+// fields of cfg, ignoring the unexported sync.Once, which
+// contains a mutex and must not be copied.
+//
+// If cfg is nil, a new zero tls.Config is returned.
+func cloneTLSConfig(cfg *tls.Config) *tls.Config {
+	if cfg == nil {
+		return &tls.Config{}
+	}
+
+	return cfg.Clone()
+}
diff --git a/go/vendor/google.golang.org/grpc/credentials/go19.go b/go/vendor/google.golang.org/grpc/credentials/go19.go
new file mode 100644
index 0000000..2a4ca1a
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/credentials/go19.go
@@ -0,0 +1,35 @@
+// +build go1.9,!appengine
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package credentials
+
+import (
+	"errors"
+	"syscall"
+)
+
+// implements the syscall.Conn interface
+func (c tlsConn) SyscallConn() (syscall.RawConn, error) {
+	conn, ok := c.rawConn.(syscall.Conn)
+	if !ok {
+		return nil, errors.New("RawConn does not implement syscall.Conn")
+	}
+	return conn.SyscallConn()
+}
diff --git a/go/vendor/google.golang.org/grpc/dialoptions.go b/go/vendor/google.golang.org/grpc/dialoptions.go
new file mode 100644
index 0000000..99b4952
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/dialoptions.go
@@ -0,0 +1,465 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"fmt"
+	"net"
+	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/internal/backoff"
+	"google.golang.org/grpc/internal/envconfig"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/stats"
+)
+
+// dialOptions configure a Dial call. dialOptions are set by the DialOption
+// values passed to Dial.
+type dialOptions struct {
+	unaryInt    UnaryClientInterceptor
+	streamInt   StreamClientInterceptor
+	cp          Compressor
+	dc          Decompressor
+	bs          backoff.Strategy
+	block       bool
+	insecure    bool
+	timeout     time.Duration
+	scChan      <-chan ServiceConfig
+	authority   string
+	copts       transport.ConnectOptions
+	callOptions []CallOption
+	// This is used by v1 balancer dial option WithBalancer to support v1
+	// balancer, and also by WithBalancerName dial option.
+	balancerBuilder balancer.Builder
+	// This is to support grpclb.
+	resolverBuilder      resolver.Builder
+	waitForHandshake     bool
+	channelzParentID     int64
+	disableServiceConfig bool
+	disableRetry         bool
+}
+
+// DialOption configures how we set up the connection.
+type DialOption interface {
+	apply(*dialOptions)
+}
+
+// EmptyDialOption does not alter the dial configuration. It can be embedded in
+// another structure to build custom dial options.
+//
+// This API is EXPERIMENTAL.
+type EmptyDialOption struct{}
+
+func (EmptyDialOption) apply(*dialOptions) {}
+
+// funcDialOption wraps a function that modifies dialOptions into an
+// implementation of the DialOption interface.
+type funcDialOption struct {
+	f func(*dialOptions)
+}
+
+func (fdo *funcDialOption) apply(do *dialOptions) {
+	fdo.f(do)
+}
+
+func newFuncDialOption(f func(*dialOptions)) *funcDialOption {
+	return &funcDialOption{
+		f: f,
+	}
+}
+
+// WithWaitForHandshake blocks until the initial settings frame is received from
+// the server before assigning RPCs to the connection. Experimental API.
+func WithWaitForHandshake() DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.waitForHandshake = true
+	})
+}
+
+// WithWriteBufferSize determines how much data can be batched before doing a
+// write on the wire. The corresponding memory allocation for this buffer will
+// be twice the size to keep syscalls low. The default value for this buffer is
+// 32KB.
+//
+// Zero will disable the write buffer such that each write will be on underlying
+// connection. Note: A Send call may not directly translate to a write.
+func WithWriteBufferSize(s int) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.WriteBufferSize = s
+	})
+}
+
+// WithReadBufferSize lets you set the size of read buffer, this determines how
+// much data can be read at most for each read syscall.
+//
+// The default value for this buffer is 32KB. Zero will disable read buffer for
+// a connection so data framer can access the underlying conn directly.
+func WithReadBufferSize(s int) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.ReadBufferSize = s
+	})
+}
+
+// WithInitialWindowSize returns a DialOption which sets the value for initial
+// window size on a stream. The lower bound for window size is 64K and any value
+// smaller than that will be ignored.
+func WithInitialWindowSize(s int32) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.InitialWindowSize = s
+	})
+}
+
+// WithInitialConnWindowSize returns a DialOption which sets the value for
+// initial window size on a connection. The lower bound for window size is 64K
+// and any value smaller than that will be ignored.
+func WithInitialConnWindowSize(s int32) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.InitialConnWindowSize = s
+	})
+}
+
+// WithMaxMsgSize returns a DialOption which sets the maximum message size the
+// client can receive.
+//
+// Deprecated: use WithDefaultCallOptions(MaxCallRecvMsgSize(s)) instead.
+func WithMaxMsgSize(s int) DialOption {
+	return WithDefaultCallOptions(MaxCallRecvMsgSize(s))
+}
+
+// WithDefaultCallOptions returns a DialOption which sets the default
+// CallOptions for calls over the connection.
+func WithDefaultCallOptions(cos ...CallOption) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.callOptions = append(o.callOptions, cos...)
+	})
+}
+
+// WithCodec returns a DialOption which sets a codec for message marshaling and
+// unmarshaling.
+//
+// Deprecated: use WithDefaultCallOptions(CallCustomCodec(c)) instead.
+func WithCodec(c Codec) DialOption {
+	return WithDefaultCallOptions(CallCustomCodec(c))
+}
+
+// WithCompressor returns a DialOption which sets a Compressor to use for
+// message compression. It has lower priority than the compressor set by the
+// UseCompressor CallOption.
+//
+// Deprecated: use UseCompressor instead.
+func WithCompressor(cp Compressor) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.cp = cp
+	})
+}
+
+// WithDecompressor returns a DialOption which sets a Decompressor to use for
+// incoming message decompression.  If incoming response messages are encoded
+// using the decompressor's Type(), it will be used.  Otherwise, the message
+// encoding will be used to look up the compressor registered via
+// encoding.RegisterCompressor, which will then be used to decompress the
+// message.  If no compressor is registered for the encoding, an Unimplemented
+// status error will be returned.
+//
+// Deprecated: use encoding.RegisterCompressor instead.
+func WithDecompressor(dc Decompressor) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.dc = dc
+	})
+}
+
+// WithBalancer returns a DialOption which sets a load balancer with the v1 API.
+// Name resolver will be ignored if this DialOption is specified.
+//
+// Deprecated: use the new balancer APIs in balancer package and
+// WithBalancerName.
+func WithBalancer(b Balancer) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.balancerBuilder = &balancerWrapperBuilder{
+			b: b,
+		}
+	})
+}
+
+// WithBalancerName sets the balancer that the ClientConn will be initialized
+// with. Balancer registered with balancerName will be used. This function
+// panics if no balancer was registered by balancerName.
+//
+// The balancer cannot be overridden by balancer option specified by service
+// config.
+//
+// This is an EXPERIMENTAL API.
+func WithBalancerName(balancerName string) DialOption {
+	builder := balancer.Get(balancerName)
+	if builder == nil {
+		panic(fmt.Sprintf("grpc.WithBalancerName: no balancer is registered for name %v", balancerName))
+	}
+	return newFuncDialOption(func(o *dialOptions) {
+		o.balancerBuilder = builder
+	})
+}
+
+// withResolverBuilder is only for grpclb.
+func withResolverBuilder(b resolver.Builder) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.resolverBuilder = b
+	})
+}
+
+// WithServiceConfig returns a DialOption which has a channel to read the
+// service configuration.
+//
+// Deprecated: service config should be received through name resolver, as
+// specified here.
+// https://github.com/grpc/grpc/blob/master/doc/service_config.md
+func WithServiceConfig(c <-chan ServiceConfig) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.scChan = c
+	})
+}
+
+// WithBackoffMaxDelay configures the dialer to use the provided maximum delay
+// when backing off after failed connection attempts.
+func WithBackoffMaxDelay(md time.Duration) DialOption {
+	return WithBackoffConfig(BackoffConfig{MaxDelay: md})
+}
+
+// WithBackoffConfig configures the dialer to use the provided backoff
+// parameters after connection failures.
+//
+// Use WithBackoffMaxDelay until more parameters on BackoffConfig are opened up
+// for use.
+func WithBackoffConfig(b BackoffConfig) DialOption {
+	return withBackoff(backoff.Exponential{
+		MaxDelay: b.MaxDelay,
+	})
+}
+
+// withBackoff sets the backoff strategy used for connectRetryNum after a failed
+// connection attempt.
+//
+// This can be exported if arbitrary backoff strategies are allowed by gRPC.
+func withBackoff(bs backoff.Strategy) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.bs = bs
+	})
+}
+
+// WithBlock returns a DialOption which makes caller of Dial blocks until the
+// underlying connection is up. Without this, Dial returns immediately and
+// connecting the server happens in background.
+func WithBlock() DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.block = true
+	})
+}
+
+// WithInsecure returns a DialOption which disables transport security for this
+// ClientConn. Note that transport security is required unless WithInsecure is
+// set.
+func WithInsecure() DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.insecure = true
+	})
+}
+
+// WithTransportCredentials returns a DialOption which configures a connection
+// level security credentials (e.g., TLS/SSL). This should not be used together
+// with WithCredentialsBundle.
+func WithTransportCredentials(creds credentials.TransportCredentials) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.TransportCredentials = creds
+	})
+}
+
+// WithPerRPCCredentials returns a DialOption which sets credentials and places
+// auth state on each outbound RPC.
+func WithPerRPCCredentials(creds credentials.PerRPCCredentials) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.PerRPCCredentials = append(o.copts.PerRPCCredentials, creds)
+	})
+}
+
+// WithCredentialsBundle returns a DialOption to set a credentials bundle for
+// the ClientConn.WithCreds. This should not be used together with
+// WithTransportCredentials.
+//
+// This API is experimental.
+func WithCredentialsBundle(b credentials.Bundle) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.CredsBundle = b
+	})
+}
+
+// WithTimeout returns a DialOption that configures a timeout for dialing a
+// ClientConn initially. This is valid if and only if WithBlock() is present.
+//
+// Deprecated: use DialContext and context.WithTimeout instead.
+func WithTimeout(d time.Duration) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.timeout = d
+	})
+}
+
+func withContextDialer(f func(context.Context, string) (net.Conn, error)) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.Dialer = f
+	})
+}
+
+func init() {
+	internal.WithContextDialer = withContextDialer
+	internal.WithResolverBuilder = withResolverBuilder
+}
+
+// WithDialer returns a DialOption that specifies a function to use for dialing
+// network addresses. If FailOnNonTempDialError() is set to true, and an error
+// is returned by f, gRPC checks the error's Temporary() method to decide if it
+// should try to reconnect to the network address.
+func WithDialer(f func(string, time.Duration) (net.Conn, error)) DialOption {
+	return withContextDialer(
+		func(ctx context.Context, addr string) (net.Conn, error) {
+			if deadline, ok := ctx.Deadline(); ok {
+				return f(addr, deadline.Sub(time.Now()))
+			}
+			return f(addr, 0)
+		})
+}
+
+// WithStatsHandler returns a DialOption that specifies the stats handler for
+// all the RPCs and underlying network connections in this ClientConn.
+func WithStatsHandler(h stats.Handler) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.StatsHandler = h
+	})
+}
+
+// FailOnNonTempDialError returns a DialOption that specifies if gRPC fails on
+// non-temporary dial errors. If f is true, and dialer returns a non-temporary
+// error, gRPC will fail the connection to the network address and won't try to
+// reconnect. The default value of FailOnNonTempDialError is false.
+//
+// FailOnNonTempDialError only affects the initial dial, and does not do
+// anything useful unless you are also using WithBlock().
+//
+// This is an EXPERIMENTAL API.
+func FailOnNonTempDialError(f bool) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.FailOnNonTempDialError = f
+	})
+}
+
+// WithUserAgent returns a DialOption that specifies a user agent string for all
+// the RPCs.
+func WithUserAgent(s string) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.UserAgent = s
+	})
+}
+
+// WithKeepaliveParams returns a DialOption that specifies keepalive parameters
+// for the client transport.
+func WithKeepaliveParams(kp keepalive.ClientParameters) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.KeepaliveParams = kp
+	})
+}
+
+// WithUnaryInterceptor returns a DialOption that specifies the interceptor for
+// unary RPCs.
+func WithUnaryInterceptor(f UnaryClientInterceptor) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.unaryInt = f
+	})
+}
+
+// WithStreamInterceptor returns a DialOption that specifies the interceptor for
+// streaming RPCs.
+func WithStreamInterceptor(f StreamClientInterceptor) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.streamInt = f
+	})
+}
+
+// WithAuthority returns a DialOption that specifies the value to be used as the
+// :authority pseudo-header. This value only works with WithInsecure and has no
+// effect if TransportCredentials are present.
+func WithAuthority(a string) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.authority = a
+	})
+}
+
+// WithChannelzParentID returns a DialOption that specifies the channelz ID of
+// current ClientConn's parent. This function is used in nested channel creation
+// (e.g. grpclb dial).
+func WithChannelzParentID(id int64) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.channelzParentID = id
+	})
+}
+
+// WithDisableServiceConfig returns a DialOption that causes grpc to ignore any
+// service config provided by the resolver and provides a hint to the resolver
+// to not fetch service configs.
+func WithDisableServiceConfig() DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.disableServiceConfig = true
+	})
+}
+
+// WithDisableRetry returns a DialOption that disables retries, even if the
+// service config enables them.  This does not impact transparent retries, which
+// will happen automatically if no data is written to the wire or if the RPC is
+// unprocessed by the remote server.
+//
+// Retry support is currently disabled by default, but will be enabled by
+// default in the future.  Until then, it may be enabled by setting the
+// environment variable "GRPC_GO_RETRY" to "on".
+//
+// This API is EXPERIMENTAL.
+func WithDisableRetry() DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.disableRetry = true
+	})
+}
+
+// WithMaxHeaderListSize returns a DialOption that specifies the maximum
+// (uncompressed) size of header list that the client is prepared to accept.
+func WithMaxHeaderListSize(s uint32) DialOption {
+	return newFuncDialOption(func(o *dialOptions) {
+		o.copts.MaxHeaderListSize = &s
+	})
+}
+
+func defaultDialOptions() dialOptions {
+	return dialOptions{
+		disableRetry: !envconfig.Retry,
+		copts: transport.ConnectOptions{
+			WriteBufferSize: defaultWriteBufSize,
+			ReadBufferSize:  defaultReadBufSize,
+		},
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/doc.go b/go/vendor/google.golang.org/grpc/doc.go
new file mode 100644
index 0000000..187adbb
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/doc.go
@@ -0,0 +1,24 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+/*
+Package grpc implements an RPC system called gRPC.
+
+See grpc.io for more information about gRPC.
+*/
+package grpc // import "google.golang.org/grpc"
diff --git a/go/vendor/google.golang.org/grpc/encoding/encoding.go b/go/vendor/google.golang.org/grpc/encoding/encoding.go
new file mode 100644
index 0000000..ade8b7c
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/encoding/encoding.go
@@ -0,0 +1,118 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package encoding defines the interface for the compressor and codec, and
+// functions to register and retrieve compressors and codecs.
+//
+// This package is EXPERIMENTAL.
+package encoding
+
+import (
+	"io"
+	"strings"
+)
+
+// Identity specifies the optional encoding for uncompressed streams.
+// It is intended for grpc internal use only.
+const Identity = "identity"
+
+// Compressor is used for compressing and decompressing when sending or
+// receiving messages.
+type Compressor interface {
+	// Compress writes the data written to wc to w after compressing it.  If an
+	// error occurs while initializing the compressor, that error is returned
+	// instead.
+	Compress(w io.Writer) (io.WriteCloser, error)
+	// Decompress reads data from r, decompresses it, and provides the
+	// uncompressed data via the returned io.Reader.  If an error occurs while
+	// initializing the decompressor, that error is returned instead.
+	Decompress(r io.Reader) (io.Reader, error)
+	// Name is the name of the compression codec and is used to set the content
+	// coding header.  The result must be static; the result cannot change
+	// between calls.
+	Name() string
+}
+
+var registeredCompressor = make(map[string]Compressor)
+
+// RegisterCompressor registers the compressor with gRPC by its name.  It can
+// be activated when sending an RPC via grpc.UseCompressor().  It will be
+// automatically accessed when receiving a message based on the content coding
+// header.  Servers also use it to send a response with the same encoding as
+// the request.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe.  If multiple Compressors are
+// registered with the same name, the one registered last will take effect.
+func RegisterCompressor(c Compressor) {
+	registeredCompressor[c.Name()] = c
+}
+
+// GetCompressor returns Compressor for the given compressor name.
+func GetCompressor(name string) Compressor {
+	return registeredCompressor[name]
+}
+
+// Codec defines the interface gRPC uses to encode and decode messages.  Note
+// that implementations of this interface must be thread safe; a Codec's
+// methods can be called from concurrent goroutines.
+type Codec interface {
+	// Marshal returns the wire format of v.
+	Marshal(v interface{}) ([]byte, error)
+	// Unmarshal parses the wire format into v.
+	Unmarshal(data []byte, v interface{}) error
+	// Name returns the name of the Codec implementation. The returned string
+	// will be used as part of content type in transmission.  The result must be
+	// static; the result cannot change between calls.
+	Name() string
+}
+
+var registeredCodecs = make(map[string]Codec)
+
+// RegisterCodec registers the provided Codec for use with all gRPC clients and
+// servers.
+//
+// The Codec will be stored and looked up by result of its Name() method, which
+// should match the content-subtype of the encoding handled by the Codec.  This
+// is case-insensitive, and is stored and looked up as lowercase.  If the
+// result of calling Name() is an empty string, RegisterCodec will panic. See
+// Content-Type on
+// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
+// more details.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe.  If multiple Compressors are
+// registered with the same name, the one registered last will take effect.
+func RegisterCodec(codec Codec) {
+	if codec == nil {
+		panic("cannot register a nil Codec")
+	}
+	contentSubtype := strings.ToLower(codec.Name())
+	if contentSubtype == "" {
+		panic("cannot register Codec with empty string result for String()")
+	}
+	registeredCodecs[contentSubtype] = codec
+}
+
+// GetCodec gets a registered Codec by content-subtype, or nil if no Codec is
+// registered for the content-subtype.
+//
+// The content-subtype is expected to be lowercase.
+func GetCodec(contentSubtype string) Codec {
+	return registeredCodecs[contentSubtype]
+}
diff --git a/go/vendor/google.golang.org/grpc/encoding/proto/proto.go b/go/vendor/google.golang.org/grpc/encoding/proto/proto.go
new file mode 100644
index 0000000..66b97a6
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/encoding/proto/proto.go
@@ -0,0 +1,110 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package proto defines the protobuf codec. Importing this package will
+// register the codec.
+package proto
+
+import (
+	"math"
+	"sync"
+
+	"github.com/golang/protobuf/proto"
+	"google.golang.org/grpc/encoding"
+)
+
+// Name is the name registered for the proto compressor.
+const Name = "proto"
+
+func init() {
+	encoding.RegisterCodec(codec{})
+}
+
+// codec is a Codec implementation with protobuf. It is the default codec for gRPC.
+type codec struct{}
+
+type cachedProtoBuffer struct {
+	lastMarshaledSize uint32
+	proto.Buffer
+}
+
+func capToMaxInt32(val int) uint32 {
+	if val > math.MaxInt32 {
+		return uint32(math.MaxInt32)
+	}
+	return uint32(val)
+}
+
+func marshal(v interface{}, cb *cachedProtoBuffer) ([]byte, error) {
+	protoMsg := v.(proto.Message)
+	newSlice := make([]byte, 0, cb.lastMarshaledSize)
+
+	cb.SetBuf(newSlice)
+	cb.Reset()
+	if err := cb.Marshal(protoMsg); err != nil {
+		return nil, err
+	}
+	out := cb.Bytes()
+	cb.lastMarshaledSize = capToMaxInt32(len(out))
+	return out, nil
+}
+
+func (codec) Marshal(v interface{}) ([]byte, error) {
+	if pm, ok := v.(proto.Marshaler); ok {
+		// object can marshal itself, no need for buffer
+		return pm.Marshal()
+	}
+
+	cb := protoBufferPool.Get().(*cachedProtoBuffer)
+	out, err := marshal(v, cb)
+
+	// put back buffer and lose the ref to the slice
+	cb.SetBuf(nil)
+	protoBufferPool.Put(cb)
+	return out, err
+}
+
+func (codec) Unmarshal(data []byte, v interface{}) error {
+	protoMsg := v.(proto.Message)
+	protoMsg.Reset()
+
+	if pu, ok := protoMsg.(proto.Unmarshaler); ok {
+		// object can unmarshal itself, no need for buffer
+		return pu.Unmarshal(data)
+	}
+
+	cb := protoBufferPool.Get().(*cachedProtoBuffer)
+	cb.SetBuf(data)
+	err := cb.Unmarshal(protoMsg)
+	cb.SetBuf(nil)
+	protoBufferPool.Put(cb)
+	return err
+}
+
+func (codec) Name() string {
+	return Name
+}
+
+var protoBufferPool = &sync.Pool{
+	New: func() interface{} {
+		return &cachedProtoBuffer{
+			Buffer:            proto.Buffer{},
+			lastMarshaledSize: 16,
+		}
+	},
+}
diff --git a/go/vendor/google.golang.org/grpc/go.mod b/go/vendor/google.golang.org/grpc/go.mod
new file mode 100644
index 0000000..1d16f5d
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/go.mod
@@ -0,0 +1,21 @@
+module google.golang.org/grpc
+
+require (
+	cloud.google.com/go v0.26.0 // indirect
+	github.com/client9/misspell v0.3.4
+	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
+	github.com/golang/lint v0.0.0-20180702182130-06c8688daad7
+	github.com/golang/mock v1.1.1
+	github.com/golang/protobuf v1.2.0
+	github.com/kisielk/gotool v1.0.0 // indirect
+	golang.org/x/lint v0.0.0-20180702182130-06c8688daad7 // indirect
+	golang.org/x/net v0.0.0-20180826012351-8a410e7b638d
+	golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be
+	golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f // indirect
+	golang.org/x/sys v0.0.0-20180830151530-49385e6e1522
+	golang.org/x/text v0.3.0 // indirect
+	golang.org/x/tools v0.0.0-20180828015842-6cd1fcedba52
+	google.golang.org/appengine v1.1.0 // indirect
+	google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8
+	honnef.co/go/tools v0.0.0-20180728063816-88497007e858
+)
diff --git a/go/vendor/google.golang.org/grpc/go.sum b/go/vendor/google.golang.org/grpc/go.sum
new file mode 100644
index 0000000..6b70e58
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/go.sum
@@ -0,0 +1,34 @@
+cloud.google.com/go v0.26.0 h1:e0WKqKTd5BnrG8aKH3J3h+QvEIQtSUcf2n5UZ5ZgLtQ=
+cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/client9/misspell v0.3.4 h1:ta993UF76GwbvJcIo3Y68y/M3WxlpEHPWIGDkJYwzJI=
+github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
+github.com/golang/lint v0.0.0-20180702182130-06c8688daad7 h1:2hRPrmiwPrp3fQX967rNJIhQPtiGXdlQWAxKbKw3VHA=
+github.com/golang/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:tluoj9z5200jBnyusfRPU2LqT6J+DAorxEvtC7LHB+E=
+github.com/golang/mock v1.1.1 h1:G5FRp8JnTd7RQH5kemVNlMeyXQAztQ3mOWV95KxsXH8=
+github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
+github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/kisielk/gotool v1.0.0 h1:AV2c/EiW3KqPNT9ZKl07ehoAGi4C5/01Cfbblndcapg=
+github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
+golang.org/x/lint v0.0.0-20180702182130-06c8688daad7 h1:00BeQWmeaGazuOrq8Q5K5d3/cHaGuFrZzpaHBXfrsUA=
+golang.org/x/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
+golang.org/x/net v0.0.0-20180826012351-8a410e7b638d h1:g9qWBGx4puODJTMVyoPrpoxPFgVGd+z1DZwjfRu4d0I=
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+golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
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+golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
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+google.golang.org/appengine v1.1.0 h1:igQkv0AAhEIvTEpD5LIpAfav2eeVO9HBTjvKHVJPRSs=
+google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
+google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8 h1:Nw54tB0rB7hY/N0NQvRW8DG4Yk3Q6T9cu9RcFQDu1tc=
+google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
+honnef.co/go/tools v0.0.0-20180728063816-88497007e858 h1:wN+eVZ7U+gqdqkec6C6VXR1OFf9a5Ul9ETzeYsYv20g=
+honnef.co/go/tools v0.0.0-20180728063816-88497007e858/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
diff --git a/go/vendor/google.golang.org/grpc/go16.go b/go/vendor/google.golang.org/grpc/go16.go
new file mode 100644
index 0000000..b1db21a
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/go16.go
@@ -0,0 +1,71 @@
+// +build go1.6,!go1.7
+
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/status"
+)
+
+// dialContext connects to the address on the named network.
+func dialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	return (&net.Dialer{Cancel: ctx.Done()}).Dial(network, address)
+}
+
+func sendHTTPRequest(ctx context.Context, req *http.Request, conn net.Conn) error {
+	req.Cancel = ctx.Done()
+	if err := req.Write(conn); err != nil {
+		return fmt.Errorf("failed to write the HTTP request: %v", err)
+	}
+	return nil
+}
+
+// toRPCErr converts an error into an error from the status package.
+func toRPCErr(err error) error {
+	if err == nil || err == io.EOF {
+		return err
+	}
+	if err == io.ErrUnexpectedEOF {
+		return status.Error(codes.Internal, err.Error())
+	}
+	if _, ok := status.FromError(err); ok {
+		return err
+	}
+	switch e := err.(type) {
+	case transport.ConnectionError:
+		return status.Error(codes.Unavailable, e.Desc)
+	default:
+		switch err {
+		case context.DeadlineExceeded:
+			return status.Error(codes.DeadlineExceeded, err.Error())
+		case context.Canceled:
+			return status.Error(codes.Canceled, err.Error())
+		}
+	}
+	return status.Error(codes.Unknown, err.Error())
+}
diff --git a/go/vendor/google.golang.org/grpc/go17.go b/go/vendor/google.golang.org/grpc/go17.go
new file mode 100644
index 0000000..71a72e8
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/go17.go
@@ -0,0 +1,72 @@
+// +build go1.7
+
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+
+	netctx "golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/status"
+)
+
+// dialContext connects to the address on the named network.
+func dialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	return (&net.Dialer{}).DialContext(ctx, network, address)
+}
+
+func sendHTTPRequest(ctx context.Context, req *http.Request, conn net.Conn) error {
+	req = req.WithContext(ctx)
+	if err := req.Write(conn); err != nil {
+		return fmt.Errorf("failed to write the HTTP request: %v", err)
+	}
+	return nil
+}
+
+// toRPCErr converts an error into an error from the status package.
+func toRPCErr(err error) error {
+	if err == nil || err == io.EOF {
+		return err
+	}
+	if err == io.ErrUnexpectedEOF {
+		return status.Error(codes.Internal, err.Error())
+	}
+	if _, ok := status.FromError(err); ok {
+		return err
+	}
+	switch e := err.(type) {
+	case transport.ConnectionError:
+		return status.Error(codes.Unavailable, e.Desc)
+	default:
+		switch err {
+		case context.DeadlineExceeded, netctx.DeadlineExceeded:
+			return status.Error(codes.DeadlineExceeded, err.Error())
+		case context.Canceled, netctx.Canceled:
+			return status.Error(codes.Canceled, err.Error())
+		}
+	}
+	return status.Error(codes.Unknown, err.Error())
+}
diff --git a/go/vendor/google.golang.org/grpc/grpclog/grpclog.go b/go/vendor/google.golang.org/grpc/grpclog/grpclog.go
new file mode 100644
index 0000000..1fabb11
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/grpclog/grpclog.go
@@ -0,0 +1,126 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package grpclog defines logging for grpc.
+//
+// All logs in transport package only go to verbose level 2.
+// All logs in other packages in grpc are logged in spite of the verbosity level.
+//
+// In the default logger,
+// severity level can be set by environment variable GRPC_GO_LOG_SEVERITY_LEVEL,
+// verbosity level can be set by GRPC_GO_LOG_VERBOSITY_LEVEL.
+package grpclog // import "google.golang.org/grpc/grpclog"
+
+import "os"
+
+var logger = newLoggerV2()
+
+// V reports whether verbosity level l is at least the requested verbose level.
+func V(l int) bool {
+	return logger.V(l)
+}
+
+// Info logs to the INFO log.
+func Info(args ...interface{}) {
+	logger.Info(args...)
+}
+
+// Infof logs to the INFO log. Arguments are handled in the manner of fmt.Printf.
+func Infof(format string, args ...interface{}) {
+	logger.Infof(format, args...)
+}
+
+// Infoln logs to the INFO log. Arguments are handled in the manner of fmt.Println.
+func Infoln(args ...interface{}) {
+	logger.Infoln(args...)
+}
+
+// Warning logs to the WARNING log.
+func Warning(args ...interface{}) {
+	logger.Warning(args...)
+}
+
+// Warningf logs to the WARNING log. Arguments are handled in the manner of fmt.Printf.
+func Warningf(format string, args ...interface{}) {
+	logger.Warningf(format, args...)
+}
+
+// Warningln logs to the WARNING log. Arguments are handled in the manner of fmt.Println.
+func Warningln(args ...interface{}) {
+	logger.Warningln(args...)
+}
+
+// Error logs to the ERROR log.
+func Error(args ...interface{}) {
+	logger.Error(args...)
+}
+
+// Errorf logs to the ERROR log. Arguments are handled in the manner of fmt.Printf.
+func Errorf(format string, args ...interface{}) {
+	logger.Errorf(format, args...)
+}
+
+// Errorln logs to the ERROR log. Arguments are handled in the manner of fmt.Println.
+func Errorln(args ...interface{}) {
+	logger.Errorln(args...)
+}
+
+// Fatal logs to the FATAL log. Arguments are handled in the manner of fmt.Print.
+// It calls os.Exit() with exit code 1.
+func Fatal(args ...interface{}) {
+	logger.Fatal(args...)
+	// Make sure fatal logs will exit.
+	os.Exit(1)
+}
+
+// Fatalf logs to the FATAL log. Arguments are handled in the manner of fmt.Printf.
+// It calles os.Exit() with exit code 1.
+func Fatalf(format string, args ...interface{}) {
+	logger.Fatalf(format, args...)
+	// Make sure fatal logs will exit.
+	os.Exit(1)
+}
+
+// Fatalln logs to the FATAL log. Arguments are handled in the manner of fmt.Println.
+// It calle os.Exit()) with exit code 1.
+func Fatalln(args ...interface{}) {
+	logger.Fatalln(args...)
+	// Make sure fatal logs will exit.
+	os.Exit(1)
+}
+
+// Print prints to the logger. Arguments are handled in the manner of fmt.Print.
+//
+// Deprecated: use Info.
+func Print(args ...interface{}) {
+	logger.Info(args...)
+}
+
+// Printf prints to the logger. Arguments are handled in the manner of fmt.Printf.
+//
+// Deprecated: use Infof.
+func Printf(format string, args ...interface{}) {
+	logger.Infof(format, args...)
+}
+
+// Println prints to the logger. Arguments are handled in the manner of fmt.Println.
+//
+// Deprecated: use Infoln.
+func Println(args ...interface{}) {
+	logger.Infoln(args...)
+}
diff --git a/go/vendor/google.golang.org/grpc/grpclog/logger.go b/go/vendor/google.golang.org/grpc/grpclog/logger.go
new file mode 100644
index 0000000..097494f
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/grpclog/logger.go
@@ -0,0 +1,85 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpclog
+
+// Logger mimics golang's standard Logger as an interface.
+//
+// Deprecated: use LoggerV2.
+type Logger interface {
+	Fatal(args ...interface{})
+	Fatalf(format string, args ...interface{})
+	Fatalln(args ...interface{})
+	Print(args ...interface{})
+	Printf(format string, args ...interface{})
+	Println(args ...interface{})
+}
+
+// SetLogger sets the logger that is used in grpc. Call only from
+// init() functions.
+//
+// Deprecated: use SetLoggerV2.
+func SetLogger(l Logger) {
+	logger = &loggerWrapper{Logger: l}
+}
+
+// loggerWrapper wraps Logger into a LoggerV2.
+type loggerWrapper struct {
+	Logger
+}
+
+func (g *loggerWrapper) Info(args ...interface{}) {
+	g.Logger.Print(args...)
+}
+
+func (g *loggerWrapper) Infoln(args ...interface{}) {
+	g.Logger.Println(args...)
+}
+
+func (g *loggerWrapper) Infof(format string, args ...interface{}) {
+	g.Logger.Printf(format, args...)
+}
+
+func (g *loggerWrapper) Warning(args ...interface{}) {
+	g.Logger.Print(args...)
+}
+
+func (g *loggerWrapper) Warningln(args ...interface{}) {
+	g.Logger.Println(args...)
+}
+
+func (g *loggerWrapper) Warningf(format string, args ...interface{}) {
+	g.Logger.Printf(format, args...)
+}
+
+func (g *loggerWrapper) Error(args ...interface{}) {
+	g.Logger.Print(args...)
+}
+
+func (g *loggerWrapper) Errorln(args ...interface{}) {
+	g.Logger.Println(args...)
+}
+
+func (g *loggerWrapper) Errorf(format string, args ...interface{}) {
+	g.Logger.Printf(format, args...)
+}
+
+func (g *loggerWrapper) V(l int) bool {
+	// Returns true for all verbose level.
+	return true
+}
diff --git a/go/vendor/google.golang.org/grpc/grpclog/loggerv2.go b/go/vendor/google.golang.org/grpc/grpclog/loggerv2.go
new file mode 100644
index 0000000..d493257
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/grpclog/loggerv2.go
@@ -0,0 +1,195 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpclog
+
+import (
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"strconv"
+)
+
+// LoggerV2 does underlying logging work for grpclog.
+type LoggerV2 interface {
+	// Info logs to INFO log. Arguments are handled in the manner of fmt.Print.
+	Info(args ...interface{})
+	// Infoln logs to INFO log. Arguments are handled in the manner of fmt.Println.
+	Infoln(args ...interface{})
+	// Infof logs to INFO log. Arguments are handled in the manner of fmt.Printf.
+	Infof(format string, args ...interface{})
+	// Warning logs to WARNING log. Arguments are handled in the manner of fmt.Print.
+	Warning(args ...interface{})
+	// Warningln logs to WARNING log. Arguments are handled in the manner of fmt.Println.
+	Warningln(args ...interface{})
+	// Warningf logs to WARNING log. Arguments are handled in the manner of fmt.Printf.
+	Warningf(format string, args ...interface{})
+	// Error logs to ERROR log. Arguments are handled in the manner of fmt.Print.
+	Error(args ...interface{})
+	// Errorln logs to ERROR log. Arguments are handled in the manner of fmt.Println.
+	Errorln(args ...interface{})
+	// Errorf logs to ERROR log. Arguments are handled in the manner of fmt.Printf.
+	Errorf(format string, args ...interface{})
+	// Fatal logs to ERROR log. Arguments are handled in the manner of fmt.Print.
+	// gRPC ensures that all Fatal logs will exit with os.Exit(1).
+	// Implementations may also call os.Exit() with a non-zero exit code.
+	Fatal(args ...interface{})
+	// Fatalln logs to ERROR log. Arguments are handled in the manner of fmt.Println.
+	// gRPC ensures that all Fatal logs will exit with os.Exit(1).
+	// Implementations may also call os.Exit() with a non-zero exit code.
+	Fatalln(args ...interface{})
+	// Fatalf logs to ERROR log. Arguments are handled in the manner of fmt.Printf.
+	// gRPC ensures that all Fatal logs will exit with os.Exit(1).
+	// Implementations may also call os.Exit() with a non-zero exit code.
+	Fatalf(format string, args ...interface{})
+	// V reports whether verbosity level l is at least the requested verbose level.
+	V(l int) bool
+}
+
+// SetLoggerV2 sets logger that is used in grpc to a V2 logger.
+// Not mutex-protected, should be called before any gRPC functions.
+func SetLoggerV2(l LoggerV2) {
+	logger = l
+}
+
+const (
+	// infoLog indicates Info severity.
+	infoLog int = iota
+	// warningLog indicates Warning severity.
+	warningLog
+	// errorLog indicates Error severity.
+	errorLog
+	// fatalLog indicates Fatal severity.
+	fatalLog
+)
+
+// severityName contains the string representation of each severity.
+var severityName = []string{
+	infoLog:    "INFO",
+	warningLog: "WARNING",
+	errorLog:   "ERROR",
+	fatalLog:   "FATAL",
+}
+
+// loggerT is the default logger used by grpclog.
+type loggerT struct {
+	m []*log.Logger
+	v int
+}
+
+// NewLoggerV2 creates a loggerV2 with the provided writers.
+// Fatal logs will be written to errorW, warningW, infoW, followed by exit(1).
+// Error logs will be written to errorW, warningW and infoW.
+// Warning logs will be written to warningW and infoW.
+// Info logs will be written to infoW.
+func NewLoggerV2(infoW, warningW, errorW io.Writer) LoggerV2 {
+	return NewLoggerV2WithVerbosity(infoW, warningW, errorW, 0)
+}
+
+// NewLoggerV2WithVerbosity creates a loggerV2 with the provided writers and
+// verbosity level.
+func NewLoggerV2WithVerbosity(infoW, warningW, errorW io.Writer, v int) LoggerV2 {
+	var m []*log.Logger
+	m = append(m, log.New(infoW, severityName[infoLog]+": ", log.LstdFlags))
+	m = append(m, log.New(io.MultiWriter(infoW, warningW), severityName[warningLog]+": ", log.LstdFlags))
+	ew := io.MultiWriter(infoW, warningW, errorW) // ew will be used for error and fatal.
+	m = append(m, log.New(ew, severityName[errorLog]+": ", log.LstdFlags))
+	m = append(m, log.New(ew, severityName[fatalLog]+": ", log.LstdFlags))
+	return &loggerT{m: m, v: v}
+}
+
+// newLoggerV2 creates a loggerV2 to be used as default logger.
+// All logs are written to stderr.
+func newLoggerV2() LoggerV2 {
+	errorW := ioutil.Discard
+	warningW := ioutil.Discard
+	infoW := ioutil.Discard
+
+	logLevel := os.Getenv("GRPC_GO_LOG_SEVERITY_LEVEL")
+	switch logLevel {
+	case "", "ERROR", "error": // If env is unset, set level to ERROR.
+		errorW = os.Stderr
+	case "WARNING", "warning":
+		warningW = os.Stderr
+	case "INFO", "info":
+		infoW = os.Stderr
+	}
+
+	var v int
+	vLevel := os.Getenv("GRPC_GO_LOG_VERBOSITY_LEVEL")
+	if vl, err := strconv.Atoi(vLevel); err == nil {
+		v = vl
+	}
+	return NewLoggerV2WithVerbosity(infoW, warningW, errorW, v)
+}
+
+func (g *loggerT) Info(args ...interface{}) {
+	g.m[infoLog].Print(args...)
+}
+
+func (g *loggerT) Infoln(args ...interface{}) {
+	g.m[infoLog].Println(args...)
+}
+
+func (g *loggerT) Infof(format string, args ...interface{}) {
+	g.m[infoLog].Printf(format, args...)
+}
+
+func (g *loggerT) Warning(args ...interface{}) {
+	g.m[warningLog].Print(args...)
+}
+
+func (g *loggerT) Warningln(args ...interface{}) {
+	g.m[warningLog].Println(args...)
+}
+
+func (g *loggerT) Warningf(format string, args ...interface{}) {
+	g.m[warningLog].Printf(format, args...)
+}
+
+func (g *loggerT) Error(args ...interface{}) {
+	g.m[errorLog].Print(args...)
+}
+
+func (g *loggerT) Errorln(args ...interface{}) {
+	g.m[errorLog].Println(args...)
+}
+
+func (g *loggerT) Errorf(format string, args ...interface{}) {
+	g.m[errorLog].Printf(format, args...)
+}
+
+func (g *loggerT) Fatal(args ...interface{}) {
+	g.m[fatalLog].Fatal(args...)
+	// No need to call os.Exit() again because log.Logger.Fatal() calls os.Exit().
+}
+
+func (g *loggerT) Fatalln(args ...interface{}) {
+	g.m[fatalLog].Fatalln(args...)
+	// No need to call os.Exit() again because log.Logger.Fatal() calls os.Exit().
+}
+
+func (g *loggerT) Fatalf(format string, args ...interface{}) {
+	g.m[fatalLog].Fatalf(format, args...)
+	// No need to call os.Exit() again because log.Logger.Fatal() calls os.Exit().
+}
+
+func (g *loggerT) V(l int) bool {
+	return l <= g.v
+}
diff --git a/go/vendor/google.golang.org/grpc/install_gae.sh b/go/vendor/google.golang.org/grpc/install_gae.sh
new file mode 100755
index 0000000..7c7bcad
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/install_gae.sh
@@ -0,0 +1,6 @@
+#!/bin/bash
+
+TMP=$(mktemp -d /tmp/sdk.XXX) \
+&& curl -o $TMP.zip "https://storage.googleapis.com/appengine-sdks/featured/go_appengine_sdk_linux_amd64-1.9.68.zip" \
+&& unzip -q $TMP.zip -d $TMP \
+&& export PATH="$PATH:$TMP/go_appengine"
diff --git a/go/vendor/google.golang.org/grpc/interceptor.go b/go/vendor/google.golang.org/grpc/interceptor.go
new file mode 100644
index 0000000..1f6ef67
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/interceptor.go
@@ -0,0 +1,77 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"golang.org/x/net/context"
+)
+
+// UnaryInvoker is called by UnaryClientInterceptor to complete RPCs.
+type UnaryInvoker func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, opts ...CallOption) error
+
+// UnaryClientInterceptor intercepts the execution of a unary RPC on the client. invoker is the handler to complete the RPC
+// and it is the responsibility of the interceptor to call it.
+// This is an EXPERIMENTAL API.
+type UnaryClientInterceptor func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, invoker UnaryInvoker, opts ...CallOption) error
+
+// Streamer is called by StreamClientInterceptor to create a ClientStream.
+type Streamer func(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, opts ...CallOption) (ClientStream, error)
+
+// StreamClientInterceptor intercepts the creation of ClientStream. It may return a custom ClientStream to intercept all I/O
+// operations. streamer is the handler to create a ClientStream and it is the responsibility of the interceptor to call it.
+// This is an EXPERIMENTAL API.
+type StreamClientInterceptor func(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, streamer Streamer, opts ...CallOption) (ClientStream, error)
+
+// UnaryServerInfo consists of various information about a unary RPC on
+// server side. All per-rpc information may be mutated by the interceptor.
+type UnaryServerInfo struct {
+	// Server is the service implementation the user provides. This is read-only.
+	Server interface{}
+	// FullMethod is the full RPC method string, i.e., /package.service/method.
+	FullMethod string
+}
+
+// UnaryHandler defines the handler invoked by UnaryServerInterceptor to complete the normal
+// execution of a unary RPC. If a UnaryHandler returns an error, it should be produced by the
+// status package, or else gRPC will use codes.Unknown as the status code and err.Error() as
+// the status message of the RPC.
+type UnaryHandler func(ctx context.Context, req interface{}) (interface{}, error)
+
+// UnaryServerInterceptor provides a hook to intercept the execution of a unary RPC on the server. info
+// contains all the information of this RPC the interceptor can operate on. And handler is the wrapper
+// of the service method implementation. It is the responsibility of the interceptor to invoke handler
+// to complete the RPC.
+type UnaryServerInterceptor func(ctx context.Context, req interface{}, info *UnaryServerInfo, handler UnaryHandler) (resp interface{}, err error)
+
+// StreamServerInfo consists of various information about a streaming RPC on
+// server side. All per-rpc information may be mutated by the interceptor.
+type StreamServerInfo struct {
+	// FullMethod is the full RPC method string, i.e., /package.service/method.
+	FullMethod string
+	// IsClientStream indicates whether the RPC is a client streaming RPC.
+	IsClientStream bool
+	// IsServerStream indicates whether the RPC is a server streaming RPC.
+	IsServerStream bool
+}
+
+// StreamServerInterceptor provides a hook to intercept the execution of a streaming RPC on the server.
+// info contains all the information of this RPC the interceptor can operate on. And handler is the
+// service method implementation. It is the responsibility of the interceptor to invoke handler to
+// complete the RPC.
+type StreamServerInterceptor func(srv interface{}, ss ServerStream, info *StreamServerInfo, handler StreamHandler) error
diff --git a/go/vendor/google.golang.org/grpc/internal/backoff/backoff.go b/go/vendor/google.golang.org/grpc/internal/backoff/backoff.go
new file mode 100644
index 0000000..1bd0cce
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/backoff/backoff.go
@@ -0,0 +1,78 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package backoff implement the backoff strategy for gRPC.
+//
+// This is kept in internal until the gRPC project decides whether or not to
+// allow alternative backoff strategies.
+package backoff
+
+import (
+	"time"
+
+	"google.golang.org/grpc/internal/grpcrand"
+)
+
+// Strategy defines the methodology for backing off after a grpc connection
+// failure.
+//
+type Strategy interface {
+	// Backoff returns the amount of time to wait before the next retry given
+	// the number of consecutive failures.
+	Backoff(retries int) time.Duration
+}
+
+const (
+	// baseDelay is the amount of time to wait before retrying after the first
+	// failure.
+	baseDelay = 1.0 * time.Second
+	// factor is applied to the backoff after each retry.
+	factor = 1.6
+	// jitter provides a range to randomize backoff delays.
+	jitter = 0.2
+)
+
+// Exponential implements exponential backoff algorithm as defined in
+// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
+type Exponential struct {
+	// MaxDelay is the upper bound of backoff delay.
+	MaxDelay time.Duration
+}
+
+// Backoff returns the amount of time to wait before the next retry given the
+// number of retries.
+func (bc Exponential) Backoff(retries int) time.Duration {
+	if retries == 0 {
+		return baseDelay
+	}
+	backoff, max := float64(baseDelay), float64(bc.MaxDelay)
+	for backoff < max && retries > 0 {
+		backoff *= factor
+		retries--
+	}
+	if backoff > max {
+		backoff = max
+	}
+	// Randomize backoff delays so that if a cluster of requests start at
+	// the same time, they won't operate in lockstep.
+	backoff *= 1 + jitter*(grpcrand.Float64()*2-1)
+	if backoff < 0 {
+		return 0
+	}
+	return time.Duration(backoff)
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/channelz/funcs.go b/go/vendor/google.golang.org/grpc/internal/channelz/funcs.go
new file mode 100644
index 0000000..6e729fa
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/channelz/funcs.go
@@ -0,0 +1,662 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package channelz defines APIs for enabling channelz service, entry
+// registration/deletion, and accessing channelz data. It also defines channelz
+// metric struct formats.
+//
+// All APIs in this package are experimental.
+package channelz
+
+import (
+	"sort"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"google.golang.org/grpc/grpclog"
+)
+
+const (
+	defaultMaxTraceEntry int32 = 30
+)
+
+var (
+	db    dbWrapper
+	idGen idGenerator
+	// EntryPerPage defines the number of channelz entries to be shown on a web page.
+	EntryPerPage  = 50
+	curState      int32
+	maxTraceEntry = defaultMaxTraceEntry
+)
+
+// TurnOn turns on channelz data collection.
+func TurnOn() {
+	if !IsOn() {
+		NewChannelzStorage()
+		atomic.StoreInt32(&curState, 1)
+	}
+}
+
+// IsOn returns whether channelz data collection is on.
+func IsOn() bool {
+	return atomic.CompareAndSwapInt32(&curState, 1, 1)
+}
+
+// SetMaxTraceEntry sets maximum number of trace entry per entity (i.e. channel/subchannel).
+// Setting it to 0 will disable channel tracing.
+func SetMaxTraceEntry(i int32) {
+	atomic.StoreInt32(&maxTraceEntry, i)
+}
+
+// ResetMaxTraceEntryToDefault resets the maximum number of trace entry per entity to default.
+func ResetMaxTraceEntryToDefault() {
+	atomic.StoreInt32(&maxTraceEntry, defaultMaxTraceEntry)
+}
+
+func getMaxTraceEntry() int {
+	i := atomic.LoadInt32(&maxTraceEntry)
+	return int(i)
+}
+
+// dbWarpper wraps around a reference to internal channelz data storage, and
+// provide synchronized functionality to set and get the reference.
+type dbWrapper struct {
+	mu sync.RWMutex
+	DB *channelMap
+}
+
+func (d *dbWrapper) set(db *channelMap) {
+	d.mu.Lock()
+	d.DB = db
+	d.mu.Unlock()
+}
+
+func (d *dbWrapper) get() *channelMap {
+	d.mu.RLock()
+	defer d.mu.RUnlock()
+	return d.DB
+}
+
+// NewChannelzStorage initializes channelz data storage and id generator.
+//
+// Note: This function is exported for testing purpose only. User should not call
+// it in most cases.
+func NewChannelzStorage() {
+	db.set(&channelMap{
+		topLevelChannels: make(map[int64]struct{}),
+		channels:         make(map[int64]*channel),
+		listenSockets:    make(map[int64]*listenSocket),
+		normalSockets:    make(map[int64]*normalSocket),
+		servers:          make(map[int64]*server),
+		subChannels:      make(map[int64]*subChannel),
+	})
+	idGen.reset()
+}
+
+// GetTopChannels returns a slice of top channel's ChannelMetric, along with a
+// boolean indicating whether there's more top channels to be queried for.
+//
+// The arg id specifies that only top channel with id at or above it will be included
+// in the result. The returned slice is up to a length of EntryPerPage, and is
+// sorted in ascending id order.
+func GetTopChannels(id int64) ([]*ChannelMetric, bool) {
+	return db.get().GetTopChannels(id)
+}
+
+// GetServers returns a slice of server's ServerMetric, along with a
+// boolean indicating whether there's more servers to be queried for.
+//
+// The arg id specifies that only server with id at or above it will be included
+// in the result. The returned slice is up to a length of EntryPerPage, and is
+// sorted in ascending id order.
+func GetServers(id int64) ([]*ServerMetric, bool) {
+	return db.get().GetServers(id)
+}
+
+// GetServerSockets returns a slice of server's (identified by id) normal socket's
+// SocketMetric, along with a boolean indicating whether there's more sockets to
+// be queried for.
+//
+// The arg startID specifies that only sockets with id at or above it will be
+// included in the result. The returned slice is up to a length of EntryPerPage,
+// and is sorted in ascending id order.
+func GetServerSockets(id int64, startID int64) ([]*SocketMetric, bool) {
+	return db.get().GetServerSockets(id, startID)
+}
+
+// GetChannel returns the ChannelMetric for the channel (identified by id).
+func GetChannel(id int64) *ChannelMetric {
+	return db.get().GetChannel(id)
+}
+
+// GetSubChannel returns the SubChannelMetric for the subchannel (identified by id).
+func GetSubChannel(id int64) *SubChannelMetric {
+	return db.get().GetSubChannel(id)
+}
+
+// GetSocket returns the SocketInternalMetric for the socket (identified by id).
+func GetSocket(id int64) *SocketMetric {
+	return db.get().GetSocket(id)
+}
+
+// RegisterChannel registers the given channel c in channelz database with ref
+// as its reference name, and add it to the child list of its parent (identified
+// by pid). pid = 0 means no parent. It returns the unique channelz tracking id
+// assigned to this channel.
+func RegisterChannel(c Channel, pid int64, ref string) int64 {
+	id := idGen.genID()
+	cn := &channel{
+		refName:     ref,
+		c:           c,
+		subChans:    make(map[int64]string),
+		nestedChans: make(map[int64]string),
+		id:          id,
+		pid:         pid,
+		trace:       &channelTrace{createdTime: time.Now(), events: make([]*TraceEvent, 0, getMaxTraceEntry())},
+	}
+	if pid == 0 {
+		db.get().addChannel(id, cn, true, pid, ref)
+	} else {
+		db.get().addChannel(id, cn, false, pid, ref)
+	}
+	return id
+}
+
+// RegisterSubChannel registers the given channel c in channelz database with ref
+// as its reference name, and add it to the child list of its parent (identified
+// by pid). It returns the unique channelz tracking id assigned to this subchannel.
+func RegisterSubChannel(c Channel, pid int64, ref string) int64 {
+	if pid == 0 {
+		grpclog.Error("a SubChannel's parent id cannot be 0")
+		return 0
+	}
+	id := idGen.genID()
+	sc := &subChannel{
+		refName: ref,
+		c:       c,
+		sockets: make(map[int64]string),
+		id:      id,
+		pid:     pid,
+		trace:   &channelTrace{createdTime: time.Now(), events: make([]*TraceEvent, 0, getMaxTraceEntry())},
+	}
+	db.get().addSubChannel(id, sc, pid, ref)
+	return id
+}
+
+// RegisterServer registers the given server s in channelz database. It returns
+// the unique channelz tracking id assigned to this server.
+func RegisterServer(s Server, ref string) int64 {
+	id := idGen.genID()
+	svr := &server{
+		refName:       ref,
+		s:             s,
+		sockets:       make(map[int64]string),
+		listenSockets: make(map[int64]string),
+		id:            id,
+	}
+	db.get().addServer(id, svr)
+	return id
+}
+
+// RegisterListenSocket registers the given listen socket s in channelz database
+// with ref as its reference name, and add it to the child list of its parent
+// (identified by pid). It returns the unique channelz tracking id assigned to
+// this listen socket.
+func RegisterListenSocket(s Socket, pid int64, ref string) int64 {
+	if pid == 0 {
+		grpclog.Error("a ListenSocket's parent id cannot be 0")
+		return 0
+	}
+	id := idGen.genID()
+	ls := &listenSocket{refName: ref, s: s, id: id, pid: pid}
+	db.get().addListenSocket(id, ls, pid, ref)
+	return id
+}
+
+// RegisterNormalSocket registers the given normal socket s in channelz database
+// with ref as its reference name, and add it to the child list of its parent
+// (identified by pid). It returns the unique channelz tracking id assigned to
+// this normal socket.
+func RegisterNormalSocket(s Socket, pid int64, ref string) int64 {
+	if pid == 0 {
+		grpclog.Error("a NormalSocket's parent id cannot be 0")
+		return 0
+	}
+	id := idGen.genID()
+	ns := &normalSocket{refName: ref, s: s, id: id, pid: pid}
+	db.get().addNormalSocket(id, ns, pid, ref)
+	return id
+}
+
+// RemoveEntry removes an entry with unique channelz trakcing id to be id from
+// channelz database.
+func RemoveEntry(id int64) {
+	db.get().removeEntry(id)
+}
+
+// TraceEventDesc is what the caller of AddTraceEvent should provide to describe the event to be added
+// to the channel trace.
+// The Parent field is optional. It is used for event that will be recorded in the entity's parent
+// trace also.
+type TraceEventDesc struct {
+	Desc     string
+	Severity Severity
+	Parent   *TraceEventDesc
+}
+
+// AddTraceEvent adds trace related to the entity with specified id, using the provided TraceEventDesc.
+func AddTraceEvent(id int64, desc *TraceEventDesc) {
+	if getMaxTraceEntry() == 0 {
+		return
+	}
+	db.get().traceEvent(id, desc)
+}
+
+// channelMap is the storage data structure for channelz.
+// Methods of channelMap can be divided in two two categories with respect to locking.
+// 1. Methods acquire the global lock.
+// 2. Methods that can only be called when global lock is held.
+// A second type of method need always to be called inside a first type of method.
+type channelMap struct {
+	mu               sync.RWMutex
+	topLevelChannels map[int64]struct{}
+	servers          map[int64]*server
+	channels         map[int64]*channel
+	subChannels      map[int64]*subChannel
+	listenSockets    map[int64]*listenSocket
+	normalSockets    map[int64]*normalSocket
+}
+
+func (c *channelMap) addServer(id int64, s *server) {
+	c.mu.Lock()
+	s.cm = c
+	c.servers[id] = s
+	c.mu.Unlock()
+}
+
+func (c *channelMap) addChannel(id int64, cn *channel, isTopChannel bool, pid int64, ref string) {
+	c.mu.Lock()
+	cn.cm = c
+	cn.trace.cm = c
+	c.channels[id] = cn
+	if isTopChannel {
+		c.topLevelChannels[id] = struct{}{}
+	} else {
+		c.findEntry(pid).addChild(id, cn)
+	}
+	c.mu.Unlock()
+}
+
+func (c *channelMap) addSubChannel(id int64, sc *subChannel, pid int64, ref string) {
+	c.mu.Lock()
+	sc.cm = c
+	sc.trace.cm = c
+	c.subChannels[id] = sc
+	c.findEntry(pid).addChild(id, sc)
+	c.mu.Unlock()
+}
+
+func (c *channelMap) addListenSocket(id int64, ls *listenSocket, pid int64, ref string) {
+	c.mu.Lock()
+	ls.cm = c
+	c.listenSockets[id] = ls
+	c.findEntry(pid).addChild(id, ls)
+	c.mu.Unlock()
+}
+
+func (c *channelMap) addNormalSocket(id int64, ns *normalSocket, pid int64, ref string) {
+	c.mu.Lock()
+	ns.cm = c
+	c.normalSockets[id] = ns
+	c.findEntry(pid).addChild(id, ns)
+	c.mu.Unlock()
+}
+
+// removeEntry triggers the removal of an entry, which may not indeed delete the entry, if it has to
+// wait on the deletion of its children and until no other entity's channel trace references it.
+// It may lead to a chain of entry deletion. For example, deleting the last socket of a gracefully
+// shutting down server will lead to the server being also deleted.
+func (c *channelMap) removeEntry(id int64) {
+	c.mu.Lock()
+	c.findEntry(id).triggerDelete()
+	c.mu.Unlock()
+}
+
+// c.mu must be held by the caller
+func (c *channelMap) decrTraceRefCount(id int64) {
+	e := c.findEntry(id)
+	if v, ok := e.(tracedChannel); ok {
+		v.decrTraceRefCount()
+		e.deleteSelfIfReady()
+	}
+}
+
+// c.mu must be held by the caller.
+func (c *channelMap) findEntry(id int64) entry {
+	var v entry
+	var ok bool
+	if v, ok = c.channels[id]; ok {
+		return v
+	}
+	if v, ok = c.subChannels[id]; ok {
+		return v
+	}
+	if v, ok = c.servers[id]; ok {
+		return v
+	}
+	if v, ok = c.listenSockets[id]; ok {
+		return v
+	}
+	if v, ok = c.normalSockets[id]; ok {
+		return v
+	}
+	return &dummyEntry{idNotFound: id}
+}
+
+// c.mu must be held by the caller
+// deleteEntry simply deletes an entry from the channelMap. Before calling this
+// method, caller must check this entry is ready to be deleted, i.e removeEntry()
+// has been called on it, and no children still exist.
+// Conditionals are ordered by the expected frequency of deletion of each entity
+// type, in order to optimize performance.
+func (c *channelMap) deleteEntry(id int64) {
+	var ok bool
+	if _, ok = c.normalSockets[id]; ok {
+		delete(c.normalSockets, id)
+		return
+	}
+	if _, ok = c.subChannels[id]; ok {
+		delete(c.subChannels, id)
+		return
+	}
+	if _, ok = c.channels[id]; ok {
+		delete(c.channels, id)
+		delete(c.topLevelChannels, id)
+		return
+	}
+	if _, ok = c.listenSockets[id]; ok {
+		delete(c.listenSockets, id)
+		return
+	}
+	if _, ok = c.servers[id]; ok {
+		delete(c.servers, id)
+		return
+	}
+}
+
+func (c *channelMap) traceEvent(id int64, desc *TraceEventDesc) {
+	c.mu.Lock()
+	child := c.findEntry(id)
+	childTC, ok := child.(tracedChannel)
+	if !ok {
+		c.mu.Unlock()
+		return
+	}
+	childTC.getChannelTrace().append(&TraceEvent{Desc: desc.Desc, Severity: desc.Severity, Timestamp: time.Now()})
+	if desc.Parent != nil {
+		parent := c.findEntry(child.getParentID())
+		var chanType RefChannelType
+		switch child.(type) {
+		case *channel:
+			chanType = RefChannel
+		case *subChannel:
+			chanType = RefSubChannel
+		}
+		if parentTC, ok := parent.(tracedChannel); ok {
+			parentTC.getChannelTrace().append(&TraceEvent{
+				Desc:      desc.Parent.Desc,
+				Severity:  desc.Parent.Severity,
+				Timestamp: time.Now(),
+				RefID:     id,
+				RefName:   childTC.getRefName(),
+				RefType:   chanType,
+			})
+			childTC.incrTraceRefCount()
+		}
+	}
+	c.mu.Unlock()
+}
+
+type int64Slice []int64
+
+func (s int64Slice) Len() int           { return len(s) }
+func (s int64Slice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s int64Slice) Less(i, j int) bool { return s[i] < s[j] }
+
+func copyMap(m map[int64]string) map[int64]string {
+	n := make(map[int64]string)
+	for k, v := range m {
+		n[k] = v
+	}
+	return n
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func (c *channelMap) GetTopChannels(id int64) ([]*ChannelMetric, bool) {
+	c.mu.RLock()
+	l := len(c.topLevelChannels)
+	ids := make([]int64, 0, l)
+	cns := make([]*channel, 0, min(l, EntryPerPage))
+
+	for k := range c.topLevelChannels {
+		ids = append(ids, k)
+	}
+	sort.Sort(int64Slice(ids))
+	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= id })
+	count := 0
+	var end bool
+	var t []*ChannelMetric
+	for i, v := range ids[idx:] {
+		if count == EntryPerPage {
+			break
+		}
+		if cn, ok := c.channels[v]; ok {
+			cns = append(cns, cn)
+			t = append(t, &ChannelMetric{
+				NestedChans: copyMap(cn.nestedChans),
+				SubChans:    copyMap(cn.subChans),
+			})
+			count++
+		}
+		if i == len(ids[idx:])-1 {
+			end = true
+			break
+		}
+	}
+	c.mu.RUnlock()
+	if count == 0 {
+		end = true
+	}
+
+	for i, cn := range cns {
+		t[i].ChannelData = cn.c.ChannelzMetric()
+		t[i].ID = cn.id
+		t[i].RefName = cn.refName
+		t[i].Trace = cn.trace.dumpData()
+	}
+	return t, end
+}
+
+func (c *channelMap) GetServers(id int64) ([]*ServerMetric, bool) {
+	c.mu.RLock()
+	l := len(c.servers)
+	ids := make([]int64, 0, l)
+	ss := make([]*server, 0, min(l, EntryPerPage))
+	for k := range c.servers {
+		ids = append(ids, k)
+	}
+	sort.Sort(int64Slice(ids))
+	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= id })
+	count := 0
+	var end bool
+	var s []*ServerMetric
+	for i, v := range ids[idx:] {
+		if count == EntryPerPage {
+			break
+		}
+		if svr, ok := c.servers[v]; ok {
+			ss = append(ss, svr)
+			s = append(s, &ServerMetric{
+				ListenSockets: copyMap(svr.listenSockets),
+			})
+			count++
+		}
+		if i == len(ids[idx:])-1 {
+			end = true
+			break
+		}
+	}
+	c.mu.RUnlock()
+	if count == 0 {
+		end = true
+	}
+
+	for i, svr := range ss {
+		s[i].ServerData = svr.s.ChannelzMetric()
+		s[i].ID = svr.id
+		s[i].RefName = svr.refName
+	}
+	return s, end
+}
+
+func (c *channelMap) GetServerSockets(id int64, startID int64) ([]*SocketMetric, bool) {
+	var svr *server
+	var ok bool
+	c.mu.RLock()
+	if svr, ok = c.servers[id]; !ok {
+		// server with id doesn't exist.
+		c.mu.RUnlock()
+		return nil, true
+	}
+	svrskts := svr.sockets
+	l := len(svrskts)
+	ids := make([]int64, 0, l)
+	sks := make([]*normalSocket, 0, min(l, EntryPerPage))
+	for k := range svrskts {
+		ids = append(ids, k)
+	}
+	sort.Sort(int64Slice(ids))
+	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= id })
+	count := 0
+	var end bool
+	for i, v := range ids[idx:] {
+		if count == EntryPerPage {
+			break
+		}
+		if ns, ok := c.normalSockets[v]; ok {
+			sks = append(sks, ns)
+			count++
+		}
+		if i == len(ids[idx:])-1 {
+			end = true
+			break
+		}
+	}
+	c.mu.RUnlock()
+	if count == 0 {
+		end = true
+	}
+	var s []*SocketMetric
+	for _, ns := range sks {
+		sm := &SocketMetric{}
+		sm.SocketData = ns.s.ChannelzMetric()
+		sm.ID = ns.id
+		sm.RefName = ns.refName
+		s = append(s, sm)
+	}
+	return s, end
+}
+
+func (c *channelMap) GetChannel(id int64) *ChannelMetric {
+	cm := &ChannelMetric{}
+	var cn *channel
+	var ok bool
+	c.mu.RLock()
+	if cn, ok = c.channels[id]; !ok {
+		// channel with id doesn't exist.
+		c.mu.RUnlock()
+		return nil
+	}
+	cm.NestedChans = copyMap(cn.nestedChans)
+	cm.SubChans = copyMap(cn.subChans)
+	c.mu.RUnlock()
+	cm.ChannelData = cn.c.ChannelzMetric()
+	cm.ID = cn.id
+	cm.RefName = cn.refName
+	cm.Trace = cn.trace.dumpData()
+	return cm
+}
+
+func (c *channelMap) GetSubChannel(id int64) *SubChannelMetric {
+	cm := &SubChannelMetric{}
+	var sc *subChannel
+	var ok bool
+	c.mu.RLock()
+	if sc, ok = c.subChannels[id]; !ok {
+		// subchannel with id doesn't exist.
+		c.mu.RUnlock()
+		return nil
+	}
+	cm.Sockets = copyMap(sc.sockets)
+	c.mu.RUnlock()
+	cm.ChannelData = sc.c.ChannelzMetric()
+	cm.ID = sc.id
+	cm.RefName = sc.refName
+	cm.Trace = sc.trace.dumpData()
+	return cm
+}
+
+func (c *channelMap) GetSocket(id int64) *SocketMetric {
+	sm := &SocketMetric{}
+	c.mu.RLock()
+	if ls, ok := c.listenSockets[id]; ok {
+		c.mu.RUnlock()
+		sm.SocketData = ls.s.ChannelzMetric()
+		sm.ID = ls.id
+		sm.RefName = ls.refName
+		return sm
+	}
+	if ns, ok := c.normalSockets[id]; ok {
+		c.mu.RUnlock()
+		sm.SocketData = ns.s.ChannelzMetric()
+		sm.ID = ns.id
+		sm.RefName = ns.refName
+		return sm
+	}
+	c.mu.RUnlock()
+	return nil
+}
+
+type idGenerator struct {
+	id int64
+}
+
+func (i *idGenerator) reset() {
+	atomic.StoreInt64(&i.id, 0)
+}
+
+func (i *idGenerator) genID() int64 {
+	return atomic.AddInt64(&i.id, 1)
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/channelz/types.go b/go/vendor/google.golang.org/grpc/internal/channelz/types.go
new file mode 100644
index 0000000..17c2274
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/channelz/types.go
@@ -0,0 +1,702 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package channelz
+
+import (
+	"net"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+)
+
+// entry represents a node in the channelz database.
+type entry interface {
+	// addChild adds a child e, whose channelz id is id to child list
+	addChild(id int64, e entry)
+	// deleteChild deletes a child with channelz id to be id from child list
+	deleteChild(id int64)
+	// triggerDelete tries to delete self from channelz database. However, if child
+	// list is not empty, then deletion from the database is on hold until the last
+	// child is deleted from database.
+	triggerDelete()
+	// deleteSelfIfReady check whether triggerDelete() has been called before, and whether child
+	// list is now empty. If both conditions are met, then delete self from database.
+	deleteSelfIfReady()
+	// getParentID returns parent ID of the entry. 0 value parent ID means no parent.
+	getParentID() int64
+}
+
+// dummyEntry is a fake entry to handle entry not found case.
+type dummyEntry struct {
+	idNotFound int64
+}
+
+func (d *dummyEntry) addChild(id int64, e entry) {
+	// Note: It is possible for a normal program to reach here under race condition.
+	// For example, there could be a race between ClientConn.Close() info being propagated
+	// to addrConn and http2Client. ClientConn.Close() cancel the context and result
+	// in http2Client to error. The error info is then caught by transport monitor
+	// and before addrConn.tearDown() is called in side ClientConn.Close(). Therefore,
+	// the addrConn will create a new transport. And when registering the new transport in
+	// channelz, its parent addrConn could have already been torn down and deleted
+	// from channelz tracking, and thus reach the code here.
+	grpclog.Infof("attempt to add child of type %T with id %d to a parent (id=%d) that doesn't currently exist", e, id, d.idNotFound)
+}
+
+func (d *dummyEntry) deleteChild(id int64) {
+	// It is possible for a normal program to reach here under race condition.
+	// Refer to the example described in addChild().
+	grpclog.Infof("attempt to delete child with id %d from a parent (id=%d) that doesn't currently exist", id, d.idNotFound)
+}
+
+func (d *dummyEntry) triggerDelete() {
+	grpclog.Warningf("attempt to delete an entry (id=%d) that doesn't currently exist", d.idNotFound)
+}
+
+func (*dummyEntry) deleteSelfIfReady() {
+	// code should not reach here. deleteSelfIfReady is always called on an existing entry.
+}
+
+func (*dummyEntry) getParentID() int64 {
+	return 0
+}
+
+// ChannelMetric defines the info channelz provides for a specific Channel, which
+// includes ChannelInternalMetric and channelz-specific data, such as channelz id,
+// child list, etc.
+type ChannelMetric struct {
+	// ID is the channelz id of this channel.
+	ID int64
+	// RefName is the human readable reference string of this channel.
+	RefName string
+	// ChannelData contains channel internal metric reported by the channel through
+	// ChannelzMetric().
+	ChannelData *ChannelInternalMetric
+	// NestedChans tracks the nested channel type children of this channel in the format of
+	// a map from nested channel channelz id to corresponding reference string.
+	NestedChans map[int64]string
+	// SubChans tracks the subchannel type children of this channel in the format of a
+	// map from subchannel channelz id to corresponding reference string.
+	SubChans map[int64]string
+	// Sockets tracks the socket type children of this channel in the format of a map
+	// from socket channelz id to corresponding reference string.
+	// Note current grpc implementation doesn't allow channel having sockets directly,
+	// therefore, this is field is unused.
+	Sockets map[int64]string
+	// Trace contains the most recent traced events.
+	Trace *ChannelTrace
+}
+
+// SubChannelMetric defines the info channelz provides for a specific SubChannel,
+// which includes ChannelInternalMetric and channelz-specific data, such as
+// channelz id, child list, etc.
+type SubChannelMetric struct {
+	// ID is the channelz id of this subchannel.
+	ID int64
+	// RefName is the human readable reference string of this subchannel.
+	RefName string
+	// ChannelData contains subchannel internal metric reported by the subchannel
+	// through ChannelzMetric().
+	ChannelData *ChannelInternalMetric
+	// NestedChans tracks the nested channel type children of this subchannel in the format of
+	// a map from nested channel channelz id to corresponding reference string.
+	// Note current grpc implementation doesn't allow subchannel to have nested channels
+	// as children, therefore, this field is unused.
+	NestedChans map[int64]string
+	// SubChans tracks the subchannel type children of this subchannel in the format of a
+	// map from subchannel channelz id to corresponding reference string.
+	// Note current grpc implementation doesn't allow subchannel to have subchannels
+	// as children, therefore, this field is unused.
+	SubChans map[int64]string
+	// Sockets tracks the socket type children of this subchannel in the format of a map
+	// from socket channelz id to corresponding reference string.
+	Sockets map[int64]string
+	// Trace contains the most recent traced events.
+	Trace *ChannelTrace
+}
+
+// ChannelInternalMetric defines the struct that the implementor of Channel interface
+// should return from ChannelzMetric().
+type ChannelInternalMetric struct {
+	// current connectivity state of the channel.
+	State connectivity.State
+	// The target this channel originally tried to connect to.  May be absent
+	Target string
+	// The number of calls started on the channel.
+	CallsStarted int64
+	// The number of calls that have completed with an OK status.
+	CallsSucceeded int64
+	// The number of calls that have a completed with a non-OK status.
+	CallsFailed int64
+	// The last time a call was started on the channel.
+	LastCallStartedTimestamp time.Time
+}
+
+// ChannelTrace stores traced events on a channel/subchannel and related info.
+type ChannelTrace struct {
+	// EventNum is the number of events that ever got traced (i.e. including those that have been deleted)
+	EventNum int64
+	// CreationTime is the creation time of the trace.
+	CreationTime time.Time
+	// Events stores the most recent trace events (up to $maxTraceEntry, newer event will overwrite the
+	// oldest one)
+	Events []*TraceEvent
+}
+
+// TraceEvent represent a single trace event
+type TraceEvent struct {
+	// Desc is a simple description of the trace event.
+	Desc string
+	// Severity states the severity of this trace event.
+	Severity Severity
+	// Timestamp is the event time.
+	Timestamp time.Time
+	// RefID is the id of the entity that gets referenced in the event. RefID is 0 if no other entity is
+	// involved in this event.
+	// e.g. SubChannel (id: 4[]) Created. --> RefID = 4, RefName = "" (inside [])
+	RefID int64
+	// RefName is the reference name for the entity that gets referenced in the event.
+	RefName string
+	// RefType indicates the referenced entity type, i.e Channel or SubChannel.
+	RefType RefChannelType
+}
+
+// Channel is the interface that should be satisfied in order to be tracked by
+// channelz as Channel or SubChannel.
+type Channel interface {
+	ChannelzMetric() *ChannelInternalMetric
+}
+
+type dummyChannel struct{}
+
+func (d *dummyChannel) ChannelzMetric() *ChannelInternalMetric {
+	return &ChannelInternalMetric{}
+}
+
+type channel struct {
+	refName     string
+	c           Channel
+	closeCalled bool
+	nestedChans map[int64]string
+	subChans    map[int64]string
+	id          int64
+	pid         int64
+	cm          *channelMap
+	trace       *channelTrace
+	// traceRefCount is the number of trace events that reference this channel.
+	// Non-zero traceRefCount means the trace of this channel cannot be deleted.
+	traceRefCount int32
+}
+
+func (c *channel) addChild(id int64, e entry) {
+	switch v := e.(type) {
+	case *subChannel:
+		c.subChans[id] = v.refName
+	case *channel:
+		c.nestedChans[id] = v.refName
+	default:
+		grpclog.Errorf("cannot add a child (id = %d) of type %T to a channel", id, e)
+	}
+}
+
+func (c *channel) deleteChild(id int64) {
+	delete(c.subChans, id)
+	delete(c.nestedChans, id)
+	c.deleteSelfIfReady()
+}
+
+func (c *channel) triggerDelete() {
+	c.closeCalled = true
+	c.deleteSelfIfReady()
+}
+
+func (c *channel) getParentID() int64 {
+	return c.pid
+}
+
+// deleteSelfFromTree tries to delete the channel from the channelz entry relation tree, which means
+// deleting the channel reference from its parent's child list.
+//
+// In order for a channel to be deleted from the tree, it must meet the criteria that, removal of the
+// corresponding grpc object has been invoked, and the channel does not have any children left.
+//
+// The returned boolean value indicates whether the channel has been successfully deleted from tree.
+func (c *channel) deleteSelfFromTree() (deleted bool) {
+	if !c.closeCalled || len(c.subChans)+len(c.nestedChans) != 0 {
+		return false
+	}
+	// not top channel
+	if c.pid != 0 {
+		c.cm.findEntry(c.pid).deleteChild(c.id)
+	}
+	return true
+}
+
+// deleteSelfFromMap checks whether it is valid to delete the channel from the map, which means
+// deleting the channel from channelz's tracking entirely. Users can no longer use id to query the
+// channel, and its memory will be garbage collected.
+//
+// The trace reference count of the channel must be 0 in order to be deleted from the map. This is
+// specified in the channel tracing gRFC that as long as some other trace has reference to an entity,
+// the trace of the referenced entity must not be deleted. In order to release the resource allocated
+// by grpc, the reference to the grpc object is reset to a dummy object.
+//
+// deleteSelfFromMap must be called after deleteSelfFromTree returns true.
+//
+// It returns a bool to indicate whether the channel can be safely deleted from map.
+func (c *channel) deleteSelfFromMap() (delete bool) {
+	if c.getTraceRefCount() != 0 {
+		c.c = &dummyChannel{}
+		return false
+	}
+	return true
+}
+
+// deleteSelfIfReady tries to delete the channel itself from the channelz database.
+// The delete process includes two steps:
+// 1. delete the channel from the entry relation tree, i.e. delete the channel reference from its
+//    parent's child list.
+// 2. delete the channel from the map, i.e. delete the channel entirely from channelz. Lookup by id
+//    will return entry not found error.
+func (c *channel) deleteSelfIfReady() {
+	if !c.deleteSelfFromTree() {
+		return
+	}
+	if !c.deleteSelfFromMap() {
+		return
+	}
+	c.cm.deleteEntry(c.id)
+	c.trace.clear()
+}
+
+func (c *channel) getChannelTrace() *channelTrace {
+	return c.trace
+}
+
+func (c *channel) incrTraceRefCount() {
+	atomic.AddInt32(&c.traceRefCount, 1)
+}
+
+func (c *channel) decrTraceRefCount() {
+	atomic.AddInt32(&c.traceRefCount, -1)
+}
+
+func (c *channel) getTraceRefCount() int {
+	i := atomic.LoadInt32(&c.traceRefCount)
+	return int(i)
+}
+
+func (c *channel) getRefName() string {
+	return c.refName
+}
+
+type subChannel struct {
+	refName       string
+	c             Channel
+	closeCalled   bool
+	sockets       map[int64]string
+	id            int64
+	pid           int64
+	cm            *channelMap
+	trace         *channelTrace
+	traceRefCount int32
+}
+
+func (sc *subChannel) addChild(id int64, e entry) {
+	if v, ok := e.(*normalSocket); ok {
+		sc.sockets[id] = v.refName
+	} else {
+		grpclog.Errorf("cannot add a child (id = %d) of type %T to a subChannel", id, e)
+	}
+}
+
+func (sc *subChannel) deleteChild(id int64) {
+	delete(sc.sockets, id)
+	sc.deleteSelfIfReady()
+}
+
+func (sc *subChannel) triggerDelete() {
+	sc.closeCalled = true
+	sc.deleteSelfIfReady()
+}
+
+func (sc *subChannel) getParentID() int64 {
+	return sc.pid
+}
+
+// deleteSelfFromTree tries to delete the subchannel from the channelz entry relation tree, which
+// means deleting the subchannel reference from its parent's child list.
+//
+// In order for a subchannel to be deleted from the tree, it must meet the criteria that, removal of
+// the corresponding grpc object has been invoked, and the subchannel does not have any children left.
+//
+// The returned boolean value indicates whether the channel has been successfully deleted from tree.
+func (sc *subChannel) deleteSelfFromTree() (deleted bool) {
+	if !sc.closeCalled || len(sc.sockets) != 0 {
+		return false
+	}
+	sc.cm.findEntry(sc.pid).deleteChild(sc.id)
+	return true
+}
+
+// deleteSelfFromMap checks whether it is valid to delete the subchannel from the map, which means
+// deleting the subchannel from channelz's tracking entirely. Users can no longer use id to query
+// the subchannel, and its memory will be garbage collected.
+//
+// The trace reference count of the subchannel must be 0 in order to be deleted from the map. This is
+// specified in the channel tracing gRFC that as long as some other trace has reference to an entity,
+// the trace of the referenced entity must not be deleted. In order to release the resource allocated
+// by grpc, the reference to the grpc object is reset to a dummy object.
+//
+// deleteSelfFromMap must be called after deleteSelfFromTree returns true.
+//
+// It returns a bool to indicate whether the channel can be safely deleted from map.
+func (sc *subChannel) deleteSelfFromMap() (delete bool) {
+	if sc.getTraceRefCount() != 0 {
+		// free the grpc struct (i.e. addrConn)
+		sc.c = &dummyChannel{}
+		return false
+	}
+	return true
+}
+
+// deleteSelfIfReady tries to delete the subchannel itself from the channelz database.
+// The delete process includes two steps:
+// 1. delete the subchannel from the entry relation tree, i.e. delete the subchannel reference from
+//    its parent's child list.
+// 2. delete the subchannel from the map, i.e. delete the subchannel entirely from channelz. Lookup
+//    by id will return entry not found error.
+func (sc *subChannel) deleteSelfIfReady() {
+	if !sc.deleteSelfFromTree() {
+		return
+	}
+	if !sc.deleteSelfFromMap() {
+		return
+	}
+	sc.cm.deleteEntry(sc.id)
+	sc.trace.clear()
+}
+
+func (sc *subChannel) getChannelTrace() *channelTrace {
+	return sc.trace
+}
+
+func (sc *subChannel) incrTraceRefCount() {
+	atomic.AddInt32(&sc.traceRefCount, 1)
+}
+
+func (sc *subChannel) decrTraceRefCount() {
+	atomic.AddInt32(&sc.traceRefCount, -1)
+}
+
+func (sc *subChannel) getTraceRefCount() int {
+	i := atomic.LoadInt32(&sc.traceRefCount)
+	return int(i)
+}
+
+func (sc *subChannel) getRefName() string {
+	return sc.refName
+}
+
+// SocketMetric defines the info channelz provides for a specific Socket, which
+// includes SocketInternalMetric and channelz-specific data, such as channelz id, etc.
+type SocketMetric struct {
+	// ID is the channelz id of this socket.
+	ID int64
+	// RefName is the human readable reference string of this socket.
+	RefName string
+	// SocketData contains socket internal metric reported by the socket through
+	// ChannelzMetric().
+	SocketData *SocketInternalMetric
+}
+
+// SocketInternalMetric defines the struct that the implementor of Socket interface
+// should return from ChannelzMetric().
+type SocketInternalMetric struct {
+	// The number of streams that have been started.
+	StreamsStarted int64
+	// The number of streams that have ended successfully:
+	// On client side, receiving frame with eos bit set.
+	// On server side, sending frame with eos bit set.
+	StreamsSucceeded int64
+	// The number of streams that have ended unsuccessfully:
+	// On client side, termination without receiving frame with eos bit set.
+	// On server side, termination without sending frame with eos bit set.
+	StreamsFailed int64
+	// The number of messages successfully sent on this socket.
+	MessagesSent     int64
+	MessagesReceived int64
+	// The number of keep alives sent.  This is typically implemented with HTTP/2
+	// ping messages.
+	KeepAlivesSent int64
+	// The last time a stream was created by this endpoint.  Usually unset for
+	// servers.
+	LastLocalStreamCreatedTimestamp time.Time
+	// The last time a stream was created by the remote endpoint.  Usually unset
+	// for clients.
+	LastRemoteStreamCreatedTimestamp time.Time
+	// The last time a message was sent by this endpoint.
+	LastMessageSentTimestamp time.Time
+	// The last time a message was received by this endpoint.
+	LastMessageReceivedTimestamp time.Time
+	// The amount of window, granted to the local endpoint by the remote endpoint.
+	// This may be slightly out of date due to network latency.  This does NOT
+	// include stream level or TCP level flow control info.
+	LocalFlowControlWindow int64
+	// The amount of window, granted to the remote endpoint by the local endpoint.
+	// This may be slightly out of date due to network latency.  This does NOT
+	// include stream level or TCP level flow control info.
+	RemoteFlowControlWindow int64
+	// The locally bound address.
+	LocalAddr net.Addr
+	// The remote bound address.  May be absent.
+	RemoteAddr net.Addr
+	// Optional, represents the name of the remote endpoint, if different than
+	// the original target name.
+	RemoteName    string
+	SocketOptions *SocketOptionData
+	Security      credentials.ChannelzSecurityValue
+}
+
+// Socket is the interface that should be satisfied in order to be tracked by
+// channelz as Socket.
+type Socket interface {
+	ChannelzMetric() *SocketInternalMetric
+}
+
+type listenSocket struct {
+	refName string
+	s       Socket
+	id      int64
+	pid     int64
+	cm      *channelMap
+}
+
+func (ls *listenSocket) addChild(id int64, e entry) {
+	grpclog.Errorf("cannot add a child (id = %d) of type %T to a listen socket", id, e)
+}
+
+func (ls *listenSocket) deleteChild(id int64) {
+	grpclog.Errorf("cannot delete a child (id = %d) from a listen socket", id)
+}
+
+func (ls *listenSocket) triggerDelete() {
+	ls.cm.deleteEntry(ls.id)
+	ls.cm.findEntry(ls.pid).deleteChild(ls.id)
+}
+
+func (ls *listenSocket) deleteSelfIfReady() {
+	grpclog.Errorf("cannot call deleteSelfIfReady on a listen socket")
+}
+
+func (ls *listenSocket) getParentID() int64 {
+	return ls.pid
+}
+
+type normalSocket struct {
+	refName string
+	s       Socket
+	id      int64
+	pid     int64
+	cm      *channelMap
+}
+
+func (ns *normalSocket) addChild(id int64, e entry) {
+	grpclog.Errorf("cannot add a child (id = %d) of type %T to a normal socket", id, e)
+}
+
+func (ns *normalSocket) deleteChild(id int64) {
+	grpclog.Errorf("cannot delete a child (id = %d) from a normal socket", id)
+}
+
+func (ns *normalSocket) triggerDelete() {
+	ns.cm.deleteEntry(ns.id)
+	ns.cm.findEntry(ns.pid).deleteChild(ns.id)
+}
+
+func (ns *normalSocket) deleteSelfIfReady() {
+	grpclog.Errorf("cannot call deleteSelfIfReady on a normal socket")
+}
+
+func (ns *normalSocket) getParentID() int64 {
+	return ns.pid
+}
+
+// ServerMetric defines the info channelz provides for a specific Server, which
+// includes ServerInternalMetric and channelz-specific data, such as channelz id,
+// child list, etc.
+type ServerMetric struct {
+	// ID is the channelz id of this server.
+	ID int64
+	// RefName is the human readable reference string of this server.
+	RefName string
+	// ServerData contains server internal metric reported by the server through
+	// ChannelzMetric().
+	ServerData *ServerInternalMetric
+	// ListenSockets tracks the listener socket type children of this server in the
+	// format of a map from socket channelz id to corresponding reference string.
+	ListenSockets map[int64]string
+}
+
+// ServerInternalMetric defines the struct that the implementor of Server interface
+// should return from ChannelzMetric().
+type ServerInternalMetric struct {
+	// The number of incoming calls started on the server.
+	CallsStarted int64
+	// The number of incoming calls that have completed with an OK status.
+	CallsSucceeded int64
+	// The number of incoming calls that have a completed with a non-OK status.
+	CallsFailed int64
+	// The last time a call was started on the server.
+	LastCallStartedTimestamp time.Time
+}
+
+// Server is the interface to be satisfied in order to be tracked by channelz as
+// Server.
+type Server interface {
+	ChannelzMetric() *ServerInternalMetric
+}
+
+type server struct {
+	refName       string
+	s             Server
+	closeCalled   bool
+	sockets       map[int64]string
+	listenSockets map[int64]string
+	id            int64
+	cm            *channelMap
+}
+
+func (s *server) addChild(id int64, e entry) {
+	switch v := e.(type) {
+	case *normalSocket:
+		s.sockets[id] = v.refName
+	case *listenSocket:
+		s.listenSockets[id] = v.refName
+	default:
+		grpclog.Errorf("cannot add a child (id = %d) of type %T to a server", id, e)
+	}
+}
+
+func (s *server) deleteChild(id int64) {
+	delete(s.sockets, id)
+	delete(s.listenSockets, id)
+	s.deleteSelfIfReady()
+}
+
+func (s *server) triggerDelete() {
+	s.closeCalled = true
+	s.deleteSelfIfReady()
+}
+
+func (s *server) deleteSelfIfReady() {
+	if !s.closeCalled || len(s.sockets)+len(s.listenSockets) != 0 {
+		return
+	}
+	s.cm.deleteEntry(s.id)
+}
+
+func (s *server) getParentID() int64 {
+	return 0
+}
+
+type tracedChannel interface {
+	getChannelTrace() *channelTrace
+	incrTraceRefCount()
+	decrTraceRefCount()
+	getRefName() string
+}
+
+type channelTrace struct {
+	cm          *channelMap
+	createdTime time.Time
+	eventCount  int64
+	mu          sync.Mutex
+	events      []*TraceEvent
+}
+
+func (c *channelTrace) append(e *TraceEvent) {
+	c.mu.Lock()
+	if len(c.events) == getMaxTraceEntry() {
+		del := c.events[0]
+		c.events = c.events[1:]
+		if del.RefID != 0 {
+			// start recursive cleanup in a goroutine to not block the call originated from grpc.
+			go func() {
+				// need to acquire c.cm.mu lock to call the unlocked attemptCleanup func.
+				c.cm.mu.Lock()
+				c.cm.decrTraceRefCount(del.RefID)
+				c.cm.mu.Unlock()
+			}()
+		}
+	}
+	e.Timestamp = time.Now()
+	c.events = append(c.events, e)
+	c.eventCount++
+	c.mu.Unlock()
+}
+
+func (c *channelTrace) clear() {
+	c.mu.Lock()
+	for _, e := range c.events {
+		if e.RefID != 0 {
+			// caller should have already held the c.cm.mu lock.
+			c.cm.decrTraceRefCount(e.RefID)
+		}
+	}
+	c.mu.Unlock()
+}
+
+// Severity is the severity level of a trace event.
+// The canonical enumeration of all valid values is here:
+// https://github.com/grpc/grpc-proto/blob/9b13d199cc0d4703c7ea26c9c330ba695866eb23/grpc/channelz/v1/channelz.proto#L126.
+type Severity int
+
+const (
+	// CtUNKNOWN indicates unknown severity of a trace event.
+	CtUNKNOWN Severity = iota
+	// CtINFO indicates info level severity of a trace event.
+	CtINFO
+	// CtWarning indicates warning level severity of a trace event.
+	CtWarning
+	// CtError indicates error level severity of a trace event.
+	CtError
+)
+
+// RefChannelType is the type of the entity being referenced in a trace event.
+type RefChannelType int
+
+const (
+	// RefChannel indicates the referenced entity is a Channel.
+	RefChannel RefChannelType = iota
+	// RefSubChannel indicates the referenced entity is a SubChannel.
+	RefSubChannel
+)
+
+func (c *channelTrace) dumpData() *ChannelTrace {
+	c.mu.Lock()
+	ct := &ChannelTrace{EventNum: c.eventCount, CreationTime: c.createdTime}
+	ct.Events = c.events[:len(c.events)]
+	c.mu.Unlock()
+	return ct
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/channelz/types_linux.go b/go/vendor/google.golang.org/grpc/internal/channelz/types_linux.go
new file mode 100644
index 0000000..0721539
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/channelz/types_linux.go
@@ -0,0 +1,53 @@
+// +build !appengine,go1.7
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package channelz
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+// SocketOptionData defines the struct to hold socket option data, and related
+// getter function to obtain info from fd.
+type SocketOptionData struct {
+	Linger      *unix.Linger
+	RecvTimeout *unix.Timeval
+	SendTimeout *unix.Timeval
+	TCPInfo     *unix.TCPInfo
+}
+
+// Getsockopt defines the function to get socket options requested by channelz.
+// It is to be passed to syscall.RawConn.Control().
+func (s *SocketOptionData) Getsockopt(fd uintptr) {
+	if v, err := unix.GetsockoptLinger(int(fd), syscall.SOL_SOCKET, syscall.SO_LINGER); err == nil {
+		s.Linger = v
+	}
+	if v, err := unix.GetsockoptTimeval(int(fd), syscall.SOL_SOCKET, syscall.SO_RCVTIMEO); err == nil {
+		s.RecvTimeout = v
+	}
+	if v, err := unix.GetsockoptTimeval(int(fd), syscall.SOL_SOCKET, syscall.SO_SNDTIMEO); err == nil {
+		s.SendTimeout = v
+	}
+	if v, err := unix.GetsockoptTCPInfo(int(fd), syscall.SOL_TCP, syscall.TCP_INFO); err == nil {
+		s.TCPInfo = v
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/channelz/types_nonlinux.go b/go/vendor/google.golang.org/grpc/internal/channelz/types_nonlinux.go
new file mode 100644
index 0000000..b246004
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/channelz/types_nonlinux.go
@@ -0,0 +1,44 @@
+// +build !linux appengine !go1.7
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package channelz
+
+import (
+	"sync"
+
+	"google.golang.org/grpc/grpclog"
+)
+
+var once sync.Once
+
+// SocketOptionData defines the struct to hold socket option data, and related
+// getter function to obtain info from fd.
+// Windows OS doesn't support Socket Option
+type SocketOptionData struct {
+}
+
+// Getsockopt defines the function to get socket options requested by channelz.
+// It is to be passed to syscall.RawConn.Control().
+// Windows OS doesn't support Socket Option
+func (s *SocketOptionData) Getsockopt(fd uintptr) {
+	once.Do(func() {
+		grpclog.Warningln("Channelz: socket options are not supported on non-linux os and appengine.")
+	})
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/channelz/util_linux_go19.go b/go/vendor/google.golang.org/grpc/internal/channelz/util_linux_go19.go
new file mode 100644
index 0000000..e1e9e32
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/channelz/util_linux_go19.go
@@ -0,0 +1,39 @@
+// +build linux,go1.9,!appengine
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package channelz
+
+import (
+	"syscall"
+)
+
+// GetSocketOption gets the socket option info of the conn.
+func GetSocketOption(socket interface{}) *SocketOptionData {
+	c, ok := socket.(syscall.Conn)
+	if !ok {
+		return nil
+	}
+	data := &SocketOptionData{}
+	if rawConn, err := c.SyscallConn(); err == nil {
+		rawConn.Control(data.Getsockopt)
+		return data
+	}
+	return nil
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/channelz/util_nonlinux_pre_go19.go b/go/vendor/google.golang.org/grpc/internal/channelz/util_nonlinux_pre_go19.go
new file mode 100644
index 0000000..1d4da95
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/channelz/util_nonlinux_pre_go19.go
@@ -0,0 +1,26 @@
+// +build !linux !go1.9 appengine
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package channelz
+
+// GetSocketOption gets the socket option info of the conn.
+func GetSocketOption(c interface{}) *SocketOptionData {
+	return nil
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/envconfig/envconfig.go b/go/vendor/google.golang.org/grpc/internal/envconfig/envconfig.go
new file mode 100644
index 0000000..3ee8740
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/envconfig/envconfig.go
@@ -0,0 +1,35 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package envconfig contains grpc settings configured by environment variables.
+package envconfig
+
+import (
+	"os"
+	"strings"
+)
+
+const (
+	prefix   = "GRPC_GO_"
+	retryStr = prefix + "RETRY"
+)
+
+var (
+	// Retry is set if retry is explicitly enabled via "GRPC_GO_RETRY=on".
+	Retry = strings.EqualFold(os.Getenv(retryStr), "on")
+)
diff --git a/go/vendor/google.golang.org/grpc/internal/grpcrand/grpcrand.go b/go/vendor/google.golang.org/grpc/internal/grpcrand/grpcrand.go
new file mode 100644
index 0000000..200b115
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/grpcrand/grpcrand.go
@@ -0,0 +1,56 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package grpcrand implements math/rand functions in a concurrent-safe way
+// with a global random source, independent of math/rand's global source.
+package grpcrand
+
+import (
+	"math/rand"
+	"sync"
+	"time"
+)
+
+var (
+	r  = rand.New(rand.NewSource(time.Now().UnixNano()))
+	mu sync.Mutex
+)
+
+// Int63n implements rand.Int63n on the grpcrand global source.
+func Int63n(n int64) int64 {
+	mu.Lock()
+	res := r.Int63n(n)
+	mu.Unlock()
+	return res
+}
+
+// Intn implements rand.Intn on the grpcrand global source.
+func Intn(n int) int {
+	mu.Lock()
+	res := r.Intn(n)
+	mu.Unlock()
+	return res
+}
+
+// Float64 implements rand.Float64 on the grpcrand global source.
+func Float64() float64 {
+	mu.Lock()
+	res := r.Float64()
+	mu.Unlock()
+	return res
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/internal.go b/go/vendor/google.golang.org/grpc/internal/internal.go
new file mode 100644
index 0000000..41f8af6
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/internal.go
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package internal contains gRPC-internal code, to avoid polluting
+// the godoc of the top-level grpc package.  It must not import any grpc
+// symbols to avoid circular dependencies.
+package internal
+
+import "golang.org/x/net/context"
+
+var (
+	// WithContextDialer is exported by clientconn.go
+	WithContextDialer interface{} // func(context.Context, string) (net.Conn, error) grpc.DialOption
+	// WithResolverBuilder is exported by clientconn.go
+	WithResolverBuilder interface{} // func (resolver.Builder) grpc.DialOption
+	// HealthCheckFunc is used to provide client-side LB channel health checking
+	HealthCheckFunc func(ctx context.Context, newStream func() (interface{}, error), reportHealth func(bool), serviceName string) error
+)
+
+const (
+	// CredsBundleModeFallback switches GoogleDefaultCreds to fallback mode.
+	CredsBundleModeFallback = "fallback"
+	// CredsBundleModeBalancer switches GoogleDefaultCreds to grpclb balancer
+	// mode.
+	CredsBundleModeBalancer = "balancer"
+	// CredsBundleModeBackendFromBalancer switches GoogleDefaultCreds to mode
+	// that supports backend returned by grpclb balancer.
+	CredsBundleModeBackendFromBalancer = "backend-from-balancer"
+)
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/bdp_estimator.go b/go/vendor/google.golang.org/grpc/internal/transport/bdp_estimator.go
new file mode 100644
index 0000000..63cd262
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/bdp_estimator.go
@@ -0,0 +1,140 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"sync"
+	"time"
+)
+
+const (
+	// bdpLimit is the maximum value the flow control windows
+	// will be increased to.
+	bdpLimit = (1 << 20) * 4
+	// alpha is a constant factor used to keep a moving average
+	// of RTTs.
+	alpha = 0.9
+	// If the current bdp sample is greater than or equal to
+	// our beta * our estimated bdp and the current bandwidth
+	// sample is the maximum bandwidth observed so far, we
+	// increase our bbp estimate by a factor of gamma.
+	beta = 0.66
+	// To put our bdp to be smaller than or equal to twice the real BDP,
+	// we should multiply our current sample with 4/3, however to round things out
+	// we use 2 as the multiplication factor.
+	gamma = 2
+)
+
+// Adding arbitrary data to ping so that its ack can be identified.
+// Easter-egg: what does the ping message say?
+var bdpPing = &ping{data: [8]byte{2, 4, 16, 16, 9, 14, 7, 7}}
+
+type bdpEstimator struct {
+	// sentAt is the time when the ping was sent.
+	sentAt time.Time
+
+	mu sync.Mutex
+	// bdp is the current bdp estimate.
+	bdp uint32
+	// sample is the number of bytes received in one measurement cycle.
+	sample uint32
+	// bwMax is the maximum bandwidth noted so far (bytes/sec).
+	bwMax float64
+	// bool to keep track of the beginning of a new measurement cycle.
+	isSent bool
+	// Callback to update the window sizes.
+	updateFlowControl func(n uint32)
+	// sampleCount is the number of samples taken so far.
+	sampleCount uint64
+	// round trip time (seconds)
+	rtt float64
+}
+
+// timesnap registers the time bdp ping was sent out so that
+// network rtt can be calculated when its ack is received.
+// It is called (by controller) when the bdpPing is
+// being written on the wire.
+func (b *bdpEstimator) timesnap(d [8]byte) {
+	if bdpPing.data != d {
+		return
+	}
+	b.sentAt = time.Now()
+}
+
+// add adds bytes to the current sample for calculating bdp.
+// It returns true only if a ping must be sent. This can be used
+// by the caller (handleData) to make decision about batching
+// a window update with it.
+func (b *bdpEstimator) add(n uint32) bool {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.bdp == bdpLimit {
+		return false
+	}
+	if !b.isSent {
+		b.isSent = true
+		b.sample = n
+		b.sentAt = time.Time{}
+		b.sampleCount++
+		return true
+	}
+	b.sample += n
+	return false
+}
+
+// calculate is called when an ack for a bdp ping is received.
+// Here we calculate the current bdp and bandwidth sample and
+// decide if the flow control windows should go up.
+func (b *bdpEstimator) calculate(d [8]byte) {
+	// Check if the ping acked for was the bdp ping.
+	if bdpPing.data != d {
+		return
+	}
+	b.mu.Lock()
+	rttSample := time.Since(b.sentAt).Seconds()
+	if b.sampleCount < 10 {
+		// Bootstrap rtt with an average of first 10 rtt samples.
+		b.rtt += (rttSample - b.rtt) / float64(b.sampleCount)
+	} else {
+		// Heed to the recent past more.
+		b.rtt += (rttSample - b.rtt) * float64(alpha)
+	}
+	b.isSent = false
+	// The number of bytes accumulated so far in the sample is smaller
+	// than or equal to 1.5 times the real BDP on a saturated connection.
+	bwCurrent := float64(b.sample) / (b.rtt * float64(1.5))
+	if bwCurrent > b.bwMax {
+		b.bwMax = bwCurrent
+	}
+	// If the current sample (which is smaller than or equal to the 1.5 times the real BDP) is
+	// greater than or equal to 2/3rd our perceived bdp AND this is the maximum bandwidth seen so far, we
+	// should update our perception of the network BDP.
+	if float64(b.sample) >= beta*float64(b.bdp) && bwCurrent == b.bwMax && b.bdp != bdpLimit {
+		sampleFloat := float64(b.sample)
+		b.bdp = uint32(gamma * sampleFloat)
+		if b.bdp > bdpLimit {
+			b.bdp = bdpLimit
+		}
+		bdp := b.bdp
+		b.mu.Unlock()
+		b.updateFlowControl(bdp)
+		return
+	}
+	b.mu.Unlock()
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/controlbuf.go b/go/vendor/google.golang.org/grpc/internal/transport/controlbuf.go
new file mode 100644
index 0000000..204ba15
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/controlbuf.go
@@ -0,0 +1,852 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"bytes"
+	"fmt"
+	"runtime"
+	"sync"
+
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+)
+
+var updateHeaderTblSize = func(e *hpack.Encoder, v uint32) {
+	e.SetMaxDynamicTableSizeLimit(v)
+}
+
+type itemNode struct {
+	it   interface{}
+	next *itemNode
+}
+
+type itemList struct {
+	head *itemNode
+	tail *itemNode
+}
+
+func (il *itemList) enqueue(i interface{}) {
+	n := &itemNode{it: i}
+	if il.tail == nil {
+		il.head, il.tail = n, n
+		return
+	}
+	il.tail.next = n
+	il.tail = n
+}
+
+// peek returns the first item in the list without removing it from the
+// list.
+func (il *itemList) peek() interface{} {
+	return il.head.it
+}
+
+func (il *itemList) dequeue() interface{} {
+	if il.head == nil {
+		return nil
+	}
+	i := il.head.it
+	il.head = il.head.next
+	if il.head == nil {
+		il.tail = nil
+	}
+	return i
+}
+
+func (il *itemList) dequeueAll() *itemNode {
+	h := il.head
+	il.head, il.tail = nil, nil
+	return h
+}
+
+func (il *itemList) isEmpty() bool {
+	return il.head == nil
+}
+
+// The following defines various control items which could flow through
+// the control buffer of transport. They represent different aspects of
+// control tasks, e.g., flow control, settings, streaming resetting, etc.
+
+// registerStream is used to register an incoming stream with loopy writer.
+type registerStream struct {
+	streamID uint32
+	wq       *writeQuota
+}
+
+// headerFrame is also used to register stream on the client-side.
+type headerFrame struct {
+	streamID   uint32
+	hf         []hpack.HeaderField
+	endStream  bool                       // Valid on server side.
+	initStream func(uint32) (bool, error) // Used only on the client side.
+	onWrite    func()
+	wq         *writeQuota    // write quota for the stream created.
+	cleanup    *cleanupStream // Valid on the server side.
+	onOrphaned func(error)    // Valid on client-side
+}
+
+type cleanupStream struct {
+	streamID uint32
+	rst      bool
+	rstCode  http2.ErrCode
+	onWrite  func()
+}
+
+type dataFrame struct {
+	streamID  uint32
+	endStream bool
+	h         []byte
+	d         []byte
+	// onEachWrite is called every time
+	// a part of d is written out.
+	onEachWrite func()
+}
+
+type incomingWindowUpdate struct {
+	streamID  uint32
+	increment uint32
+}
+
+type outgoingWindowUpdate struct {
+	streamID  uint32
+	increment uint32
+}
+
+type incomingSettings struct {
+	ss []http2.Setting
+}
+
+type outgoingSettings struct {
+	ss []http2.Setting
+}
+
+type incomingGoAway struct {
+}
+
+type goAway struct {
+	code      http2.ErrCode
+	debugData []byte
+	headsUp   bool
+	closeConn bool
+}
+
+type ping struct {
+	ack  bool
+	data [8]byte
+}
+
+type outFlowControlSizeRequest struct {
+	resp chan uint32
+}
+
+type outStreamState int
+
+const (
+	active outStreamState = iota
+	empty
+	waitingOnStreamQuota
+)
+
+type outStream struct {
+	id               uint32
+	state            outStreamState
+	itl              *itemList
+	bytesOutStanding int
+	wq               *writeQuota
+
+	next *outStream
+	prev *outStream
+}
+
+func (s *outStream) deleteSelf() {
+	if s.prev != nil {
+		s.prev.next = s.next
+	}
+	if s.next != nil {
+		s.next.prev = s.prev
+	}
+	s.next, s.prev = nil, nil
+}
+
+type outStreamList struct {
+	// Following are sentinel objects that mark the
+	// beginning and end of the list. They do not
+	// contain any item lists. All valid objects are
+	// inserted in between them.
+	// This is needed so that an outStream object can
+	// deleteSelf() in O(1) time without knowing which
+	// list it belongs to.
+	head *outStream
+	tail *outStream
+}
+
+func newOutStreamList() *outStreamList {
+	head, tail := new(outStream), new(outStream)
+	head.next = tail
+	tail.prev = head
+	return &outStreamList{
+		head: head,
+		tail: tail,
+	}
+}
+
+func (l *outStreamList) enqueue(s *outStream) {
+	e := l.tail.prev
+	e.next = s
+	s.prev = e
+	s.next = l.tail
+	l.tail.prev = s
+}
+
+// remove from the beginning of the list.
+func (l *outStreamList) dequeue() *outStream {
+	b := l.head.next
+	if b == l.tail {
+		return nil
+	}
+	b.deleteSelf()
+	return b
+}
+
+// controlBuffer is a way to pass information to loopy.
+// Information is passed as specific struct types called control frames.
+// A control frame not only represents data, messages or headers to be sent out
+// but can also be used to instruct loopy to update its internal state.
+// It shouldn't be confused with an HTTP2 frame, although some of the control frames
+// like dataFrame and headerFrame do go out on wire as HTTP2 frames.
+type controlBuffer struct {
+	ch              chan struct{}
+	done            <-chan struct{}
+	mu              sync.Mutex
+	consumerWaiting bool
+	list            *itemList
+	err             error
+}
+
+func newControlBuffer(done <-chan struct{}) *controlBuffer {
+	return &controlBuffer{
+		ch:   make(chan struct{}, 1),
+		list: &itemList{},
+		done: done,
+	}
+}
+
+func (c *controlBuffer) put(it interface{}) error {
+	_, err := c.executeAndPut(nil, it)
+	return err
+}
+
+func (c *controlBuffer) executeAndPut(f func(it interface{}) bool, it interface{}) (bool, error) {
+	var wakeUp bool
+	c.mu.Lock()
+	if c.err != nil {
+		c.mu.Unlock()
+		return false, c.err
+	}
+	if f != nil {
+		if !f(it) { // f wasn't successful
+			c.mu.Unlock()
+			return false, nil
+		}
+	}
+	if c.consumerWaiting {
+		wakeUp = true
+		c.consumerWaiting = false
+	}
+	c.list.enqueue(it)
+	c.mu.Unlock()
+	if wakeUp {
+		select {
+		case c.ch <- struct{}{}:
+		default:
+		}
+	}
+	return true, nil
+}
+
+// Note argument f should never be nil.
+func (c *controlBuffer) execute(f func(it interface{}) bool, it interface{}) (bool, error) {
+	c.mu.Lock()
+	if c.err != nil {
+		c.mu.Unlock()
+		return false, c.err
+	}
+	if !f(it) { // f wasn't successful
+		c.mu.Unlock()
+		return false, nil
+	}
+	c.mu.Unlock()
+	return true, nil
+}
+
+func (c *controlBuffer) get(block bool) (interface{}, error) {
+	for {
+		c.mu.Lock()
+		if c.err != nil {
+			c.mu.Unlock()
+			return nil, c.err
+		}
+		if !c.list.isEmpty() {
+			h := c.list.dequeue()
+			c.mu.Unlock()
+			return h, nil
+		}
+		if !block {
+			c.mu.Unlock()
+			return nil, nil
+		}
+		c.consumerWaiting = true
+		c.mu.Unlock()
+		select {
+		case <-c.ch:
+		case <-c.done:
+			c.finish()
+			return nil, ErrConnClosing
+		}
+	}
+}
+
+func (c *controlBuffer) finish() {
+	c.mu.Lock()
+	if c.err != nil {
+		c.mu.Unlock()
+		return
+	}
+	c.err = ErrConnClosing
+	// There may be headers for streams in the control buffer.
+	// These streams need to be cleaned out since the transport
+	// is still not aware of these yet.
+	for head := c.list.dequeueAll(); head != nil; head = head.next {
+		hdr, ok := head.it.(*headerFrame)
+		if !ok {
+			continue
+		}
+		if hdr.onOrphaned != nil { // It will be nil on the server-side.
+			hdr.onOrphaned(ErrConnClosing)
+		}
+	}
+	c.mu.Unlock()
+}
+
+type side int
+
+const (
+	clientSide side = iota
+	serverSide
+)
+
+// Loopy receives frames from the control buffer.
+// Each frame is handled individually; most of the work done by loopy goes
+// into handling data frames. Loopy maintains a queue of active streams, and each
+// stream maintains a queue of data frames; as loopy receives data frames
+// it gets added to the queue of the relevant stream.
+// Loopy goes over this list of active streams by processing one node every iteration,
+// thereby closely resemebling to a round-robin scheduling over all streams. While
+// processing a stream, loopy writes out data bytes from this stream capped by the min
+// of http2MaxFrameLen, connection-level flow control and stream-level flow control.
+type loopyWriter struct {
+	side      side
+	cbuf      *controlBuffer
+	sendQuota uint32
+	oiws      uint32 // outbound initial window size.
+	// estdStreams is map of all established streams that are not cleaned-up yet.
+	// On client-side, this is all streams whose headers were sent out.
+	// On server-side, this is all streams whose headers were received.
+	estdStreams map[uint32]*outStream // Established streams.
+	// activeStreams is a linked-list of all streams that have data to send and some
+	// stream-level flow control quota.
+	// Each of these streams internally have a list of data items(and perhaps trailers
+	// on the server-side) to be sent out.
+	activeStreams *outStreamList
+	framer        *framer
+	hBuf          *bytes.Buffer  // The buffer for HPACK encoding.
+	hEnc          *hpack.Encoder // HPACK encoder.
+	bdpEst        *bdpEstimator
+	draining      bool
+
+	// Side-specific handlers
+	ssGoAwayHandler func(*goAway) (bool, error)
+}
+
+func newLoopyWriter(s side, fr *framer, cbuf *controlBuffer, bdpEst *bdpEstimator) *loopyWriter {
+	var buf bytes.Buffer
+	l := &loopyWriter{
+		side:          s,
+		cbuf:          cbuf,
+		sendQuota:     defaultWindowSize,
+		oiws:          defaultWindowSize,
+		estdStreams:   make(map[uint32]*outStream),
+		activeStreams: newOutStreamList(),
+		framer:        fr,
+		hBuf:          &buf,
+		hEnc:          hpack.NewEncoder(&buf),
+		bdpEst:        bdpEst,
+	}
+	return l
+}
+
+const minBatchSize = 1000
+
+// run should be run in a separate goroutine.
+// It reads control frames from controlBuf and processes them by:
+// 1. Updating loopy's internal state, or/and
+// 2. Writing out HTTP2 frames on the wire.
+//
+// Loopy keeps all active streams with data to send in a linked-list.
+// All streams in the activeStreams linked-list must have both:
+// 1. Data to send, and
+// 2. Stream level flow control quota available.
+//
+// In each iteration of run loop, other than processing the incoming control
+// frame, loopy calls processData, which processes one node from the activeStreams linked-list.
+// This results in writing of HTTP2 frames into an underlying write buffer.
+// When there's no more control frames to read from controlBuf, loopy flushes the write buffer.
+// As an optimization, to increase the batch size for each flush, loopy yields the processor, once
+// if the batch size is too low to give stream goroutines a chance to fill it up.
+func (l *loopyWriter) run() (err error) {
+	defer func() {
+		if err == ErrConnClosing {
+			// Don't log ErrConnClosing as error since it happens
+			// 1. When the connection is closed by some other known issue.
+			// 2. User closed the connection.
+			// 3. A graceful close of connection.
+			infof("transport: loopyWriter.run returning. %v", err)
+			err = nil
+		}
+	}()
+	for {
+		it, err := l.cbuf.get(true)
+		if err != nil {
+			return err
+		}
+		if err = l.handle(it); err != nil {
+			return err
+		}
+		if _, err = l.processData(); err != nil {
+			return err
+		}
+		gosched := true
+	hasdata:
+		for {
+			it, err := l.cbuf.get(false)
+			if err != nil {
+				return err
+			}
+			if it != nil {
+				if err = l.handle(it); err != nil {
+					return err
+				}
+				if _, err = l.processData(); err != nil {
+					return err
+				}
+				continue hasdata
+			}
+			isEmpty, err := l.processData()
+			if err != nil {
+				return err
+			}
+			if !isEmpty {
+				continue hasdata
+			}
+			if gosched {
+				gosched = false
+				if l.framer.writer.offset < minBatchSize {
+					runtime.Gosched()
+					continue hasdata
+				}
+			}
+			l.framer.writer.Flush()
+			break hasdata
+
+		}
+	}
+}
+
+func (l *loopyWriter) outgoingWindowUpdateHandler(w *outgoingWindowUpdate) error {
+	return l.framer.fr.WriteWindowUpdate(w.streamID, w.increment)
+}
+
+func (l *loopyWriter) incomingWindowUpdateHandler(w *incomingWindowUpdate) error {
+	// Otherwise update the quota.
+	if w.streamID == 0 {
+		l.sendQuota += w.increment
+		return nil
+	}
+	// Find the stream and update it.
+	if str, ok := l.estdStreams[w.streamID]; ok {
+		str.bytesOutStanding -= int(w.increment)
+		if strQuota := int(l.oiws) - str.bytesOutStanding; strQuota > 0 && str.state == waitingOnStreamQuota {
+			str.state = active
+			l.activeStreams.enqueue(str)
+			return nil
+		}
+	}
+	return nil
+}
+
+func (l *loopyWriter) outgoingSettingsHandler(s *outgoingSettings) error {
+	return l.framer.fr.WriteSettings(s.ss...)
+}
+
+func (l *loopyWriter) incomingSettingsHandler(s *incomingSettings) error {
+	if err := l.applySettings(s.ss); err != nil {
+		return err
+	}
+	return l.framer.fr.WriteSettingsAck()
+}
+
+func (l *loopyWriter) registerStreamHandler(h *registerStream) error {
+	str := &outStream{
+		id:    h.streamID,
+		state: empty,
+		itl:   &itemList{},
+		wq:    h.wq,
+	}
+	l.estdStreams[h.streamID] = str
+	return nil
+}
+
+func (l *loopyWriter) headerHandler(h *headerFrame) error {
+	if l.side == serverSide {
+		str, ok := l.estdStreams[h.streamID]
+		if !ok {
+			warningf("transport: loopy doesn't recognize the stream: %d", h.streamID)
+			return nil
+		}
+		// Case 1.A: Server is responding back with headers.
+		if !h.endStream {
+			return l.writeHeader(h.streamID, h.endStream, h.hf, h.onWrite)
+		}
+		// else:  Case 1.B: Server wants to close stream.
+
+		if str.state != empty { // either active or waiting on stream quota.
+			// add it str's list of items.
+			str.itl.enqueue(h)
+			return nil
+		}
+		if err := l.writeHeader(h.streamID, h.endStream, h.hf, h.onWrite); err != nil {
+			return err
+		}
+		return l.cleanupStreamHandler(h.cleanup)
+	}
+	// Case 2: Client wants to originate stream.
+	str := &outStream{
+		id:    h.streamID,
+		state: empty,
+		itl:   &itemList{},
+		wq:    h.wq,
+	}
+	str.itl.enqueue(h)
+	return l.originateStream(str)
+}
+
+func (l *loopyWriter) originateStream(str *outStream) error {
+	hdr := str.itl.dequeue().(*headerFrame)
+	sendPing, err := hdr.initStream(str.id)
+	if err != nil {
+		if err == ErrConnClosing {
+			return err
+		}
+		// Other errors(errStreamDrain) need not close transport.
+		return nil
+	}
+	if err = l.writeHeader(str.id, hdr.endStream, hdr.hf, hdr.onWrite); err != nil {
+		return err
+	}
+	l.estdStreams[str.id] = str
+	if sendPing {
+		return l.pingHandler(&ping{data: [8]byte{}})
+	}
+	return nil
+}
+
+func (l *loopyWriter) writeHeader(streamID uint32, endStream bool, hf []hpack.HeaderField, onWrite func()) error {
+	if onWrite != nil {
+		onWrite()
+	}
+	l.hBuf.Reset()
+	for _, f := range hf {
+		if err := l.hEnc.WriteField(f); err != nil {
+			warningf("transport: loopyWriter.writeHeader encountered error while encoding headers:", err)
+		}
+	}
+	var (
+		err               error
+		endHeaders, first bool
+	)
+	first = true
+	for !endHeaders {
+		size := l.hBuf.Len()
+		if size > http2MaxFrameLen {
+			size = http2MaxFrameLen
+		} else {
+			endHeaders = true
+		}
+		if first {
+			first = false
+			err = l.framer.fr.WriteHeaders(http2.HeadersFrameParam{
+				StreamID:      streamID,
+				BlockFragment: l.hBuf.Next(size),
+				EndStream:     endStream,
+				EndHeaders:    endHeaders,
+			})
+		} else {
+			err = l.framer.fr.WriteContinuation(
+				streamID,
+				endHeaders,
+				l.hBuf.Next(size),
+			)
+		}
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (l *loopyWriter) preprocessData(df *dataFrame) error {
+	str, ok := l.estdStreams[df.streamID]
+	if !ok {
+		return nil
+	}
+	// If we got data for a stream it means that
+	// stream was originated and the headers were sent out.
+	str.itl.enqueue(df)
+	if str.state == empty {
+		str.state = active
+		l.activeStreams.enqueue(str)
+	}
+	return nil
+}
+
+func (l *loopyWriter) pingHandler(p *ping) error {
+	if !p.ack {
+		l.bdpEst.timesnap(p.data)
+	}
+	return l.framer.fr.WritePing(p.ack, p.data)
+
+}
+
+func (l *loopyWriter) outFlowControlSizeRequestHandler(o *outFlowControlSizeRequest) error {
+	o.resp <- l.sendQuota
+	return nil
+}
+
+func (l *loopyWriter) cleanupStreamHandler(c *cleanupStream) error {
+	c.onWrite()
+	if str, ok := l.estdStreams[c.streamID]; ok {
+		// On the server side it could be a trailers-only response or
+		// a RST_STREAM before stream initialization thus the stream might
+		// not be established yet.
+		delete(l.estdStreams, c.streamID)
+		str.deleteSelf()
+	}
+	if c.rst { // If RST_STREAM needs to be sent.
+		if err := l.framer.fr.WriteRSTStream(c.streamID, c.rstCode); err != nil {
+			return err
+		}
+	}
+	if l.side == clientSide && l.draining && len(l.estdStreams) == 0 {
+		return ErrConnClosing
+	}
+	return nil
+}
+
+func (l *loopyWriter) incomingGoAwayHandler(*incomingGoAway) error {
+	if l.side == clientSide {
+		l.draining = true
+		if len(l.estdStreams) == 0 {
+			return ErrConnClosing
+		}
+	}
+	return nil
+}
+
+func (l *loopyWriter) goAwayHandler(g *goAway) error {
+	// Handling of outgoing GoAway is very specific to side.
+	if l.ssGoAwayHandler != nil {
+		draining, err := l.ssGoAwayHandler(g)
+		if err != nil {
+			return err
+		}
+		l.draining = draining
+	}
+	return nil
+}
+
+func (l *loopyWriter) handle(i interface{}) error {
+	switch i := i.(type) {
+	case *incomingWindowUpdate:
+		return l.incomingWindowUpdateHandler(i)
+	case *outgoingWindowUpdate:
+		return l.outgoingWindowUpdateHandler(i)
+	case *incomingSettings:
+		return l.incomingSettingsHandler(i)
+	case *outgoingSettings:
+		return l.outgoingSettingsHandler(i)
+	case *headerFrame:
+		return l.headerHandler(i)
+	case *registerStream:
+		return l.registerStreamHandler(i)
+	case *cleanupStream:
+		return l.cleanupStreamHandler(i)
+	case *incomingGoAway:
+		return l.incomingGoAwayHandler(i)
+	case *dataFrame:
+		return l.preprocessData(i)
+	case *ping:
+		return l.pingHandler(i)
+	case *goAway:
+		return l.goAwayHandler(i)
+	case *outFlowControlSizeRequest:
+		return l.outFlowControlSizeRequestHandler(i)
+	default:
+		return fmt.Errorf("transport: unknown control message type %T", i)
+	}
+}
+
+func (l *loopyWriter) applySettings(ss []http2.Setting) error {
+	for _, s := range ss {
+		switch s.ID {
+		case http2.SettingInitialWindowSize:
+			o := l.oiws
+			l.oiws = s.Val
+			if o < l.oiws {
+				// If the new limit is greater make all depleted streams active.
+				for _, stream := range l.estdStreams {
+					if stream.state == waitingOnStreamQuota {
+						stream.state = active
+						l.activeStreams.enqueue(stream)
+					}
+				}
+			}
+		case http2.SettingHeaderTableSize:
+			updateHeaderTblSize(l.hEnc, s.Val)
+		}
+	}
+	return nil
+}
+
+// processData removes the first stream from active streams, writes out at most 16KB
+// of its data and then puts it at the end of activeStreams if there's still more data
+// to be sent and stream has some stream-level flow control.
+func (l *loopyWriter) processData() (bool, error) {
+	if l.sendQuota == 0 {
+		return true, nil
+	}
+	str := l.activeStreams.dequeue() // Remove the first stream.
+	if str == nil {
+		return true, nil
+	}
+	dataItem := str.itl.peek().(*dataFrame) // Peek at the first data item this stream.
+	// A data item is represented by a dataFrame, since it later translates into
+	// multiple HTTP2 data frames.
+	// Every dataFrame has two buffers; h that keeps grpc-message header and d that is acutal data.
+	// As an optimization to keep wire traffic low, data from d is copied to h to make as big as the
+	// maximum possilbe HTTP2 frame size.
+
+	if len(dataItem.h) == 0 && len(dataItem.d) == 0 { // Empty data frame
+		// Client sends out empty data frame with endStream = true
+		if err := l.framer.fr.WriteData(dataItem.streamID, dataItem.endStream, nil); err != nil {
+			return false, err
+		}
+		str.itl.dequeue() // remove the empty data item from stream
+		if str.itl.isEmpty() {
+			str.state = empty
+		} else if trailer, ok := str.itl.peek().(*headerFrame); ok { // the next item is trailers.
+			if err := l.writeHeader(trailer.streamID, trailer.endStream, trailer.hf, trailer.onWrite); err != nil {
+				return false, err
+			}
+			if err := l.cleanupStreamHandler(trailer.cleanup); err != nil {
+				return false, nil
+			}
+		} else {
+			l.activeStreams.enqueue(str)
+		}
+		return false, nil
+	}
+	var (
+		idx int
+		buf []byte
+	)
+	if len(dataItem.h) != 0 { // data header has not been written out yet.
+		buf = dataItem.h
+	} else {
+		idx = 1
+		buf = dataItem.d
+	}
+	size := http2MaxFrameLen
+	if len(buf) < size {
+		size = len(buf)
+	}
+	if strQuota := int(l.oiws) - str.bytesOutStanding; strQuota <= 0 { // stream-level flow control.
+		str.state = waitingOnStreamQuota
+		return false, nil
+	} else if strQuota < size {
+		size = strQuota
+	}
+
+	if l.sendQuota < uint32(size) { // connection-level flow control.
+		size = int(l.sendQuota)
+	}
+	// Now that outgoing flow controls are checked we can replenish str's write quota
+	str.wq.replenish(size)
+	var endStream bool
+	// If this is the last data message on this stream and all of it can be written in this iteration.
+	if dataItem.endStream && size == len(buf) {
+		// buf contains either data or it contains header but data is empty.
+		if idx == 1 || len(dataItem.d) == 0 {
+			endStream = true
+		}
+	}
+	if dataItem.onEachWrite != nil {
+		dataItem.onEachWrite()
+	}
+	if err := l.framer.fr.WriteData(dataItem.streamID, endStream, buf[:size]); err != nil {
+		return false, err
+	}
+	buf = buf[size:]
+	str.bytesOutStanding += size
+	l.sendQuota -= uint32(size)
+	if idx == 0 {
+		dataItem.h = buf
+	} else {
+		dataItem.d = buf
+	}
+
+	if len(dataItem.h) == 0 && len(dataItem.d) == 0 { // All the data from that message was written out.
+		str.itl.dequeue()
+	}
+	if str.itl.isEmpty() {
+		str.state = empty
+	} else if trailer, ok := str.itl.peek().(*headerFrame); ok { // The next item is trailers.
+		if err := l.writeHeader(trailer.streamID, trailer.endStream, trailer.hf, trailer.onWrite); err != nil {
+			return false, err
+		}
+		if err := l.cleanupStreamHandler(trailer.cleanup); err != nil {
+			return false, err
+		}
+	} else if int(l.oiws)-str.bytesOutStanding <= 0 { // Ran out of stream quota.
+		str.state = waitingOnStreamQuota
+	} else { // Otherwise add it back to the list of active streams.
+		l.activeStreams.enqueue(str)
+	}
+	return false, nil
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/defaults.go b/go/vendor/google.golang.org/grpc/internal/transport/defaults.go
new file mode 100644
index 0000000..9fa306b
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/defaults.go
@@ -0,0 +1,49 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"math"
+	"time"
+)
+
+const (
+	// The default value of flow control window size in HTTP2 spec.
+	defaultWindowSize = 65535
+	// The initial window size for flow control.
+	initialWindowSize             = defaultWindowSize // for an RPC
+	infinity                      = time.Duration(math.MaxInt64)
+	defaultClientKeepaliveTime    = infinity
+	defaultClientKeepaliveTimeout = 20 * time.Second
+	defaultMaxStreamsClient       = 100
+	defaultMaxConnectionIdle      = infinity
+	defaultMaxConnectionAge       = infinity
+	defaultMaxConnectionAgeGrace  = infinity
+	defaultServerKeepaliveTime    = 2 * time.Hour
+	defaultServerKeepaliveTimeout = 20 * time.Second
+	defaultKeepalivePolicyMinTime = 5 * time.Minute
+	// max window limit set by HTTP2 Specs.
+	maxWindowSize = math.MaxInt32
+	// defaultWriteQuota is the default value for number of data
+	// bytes that each stream can schedule before some of it being
+	// flushed out.
+	defaultWriteQuota              = 64 * 1024
+	defaultClientMaxHeaderListSize = uint32(16 << 20)
+	defaultServerMaxHeaderListSize = uint32(16 << 20)
+)
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/flowcontrol.go b/go/vendor/google.golang.org/grpc/internal/transport/flowcontrol.go
new file mode 100644
index 0000000..5ea997a
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/flowcontrol.go
@@ -0,0 +1,218 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"fmt"
+	"math"
+	"sync"
+	"sync/atomic"
+)
+
+// writeQuota is a soft limit on the amount of data a stream can
+// schedule before some of it is written out.
+type writeQuota struct {
+	quota int32
+	// get waits on read from when quota goes less than or equal to zero.
+	// replenish writes on it when quota goes positive again.
+	ch chan struct{}
+	// done is triggered in error case.
+	done <-chan struct{}
+	// replenish is called by loopyWriter to give quota back to.
+	// It is implemented as a field so that it can be updated
+	// by tests.
+	replenish func(n int)
+}
+
+func newWriteQuota(sz int32, done <-chan struct{}) *writeQuota {
+	w := &writeQuota{
+		quota: sz,
+		ch:    make(chan struct{}, 1),
+		done:  done,
+	}
+	w.replenish = w.realReplenish
+	return w
+}
+
+func (w *writeQuota) get(sz int32) error {
+	for {
+		if atomic.LoadInt32(&w.quota) > 0 {
+			atomic.AddInt32(&w.quota, -sz)
+			return nil
+		}
+		select {
+		case <-w.ch:
+			continue
+		case <-w.done:
+			return errStreamDone
+		}
+	}
+}
+
+func (w *writeQuota) realReplenish(n int) {
+	sz := int32(n)
+	a := atomic.AddInt32(&w.quota, sz)
+	b := a - sz
+	if b <= 0 && a > 0 {
+		select {
+		case w.ch <- struct{}{}:
+		default:
+		}
+	}
+}
+
+type trInFlow struct {
+	limit               uint32
+	unacked             uint32
+	effectiveWindowSize uint32
+}
+
+func (f *trInFlow) newLimit(n uint32) uint32 {
+	d := n - f.limit
+	f.limit = n
+	f.updateEffectiveWindowSize()
+	return d
+}
+
+func (f *trInFlow) onData(n uint32) uint32 {
+	f.unacked += n
+	if f.unacked >= f.limit/4 {
+		w := f.unacked
+		f.unacked = 0
+		f.updateEffectiveWindowSize()
+		return w
+	}
+	f.updateEffectiveWindowSize()
+	return 0
+}
+
+func (f *trInFlow) reset() uint32 {
+	w := f.unacked
+	f.unacked = 0
+	f.updateEffectiveWindowSize()
+	return w
+}
+
+func (f *trInFlow) updateEffectiveWindowSize() {
+	atomic.StoreUint32(&f.effectiveWindowSize, f.limit-f.unacked)
+}
+
+func (f *trInFlow) getSize() uint32 {
+	return atomic.LoadUint32(&f.effectiveWindowSize)
+}
+
+// TODO(mmukhi): Simplify this code.
+// inFlow deals with inbound flow control
+type inFlow struct {
+	mu sync.Mutex
+	// The inbound flow control limit for pending data.
+	limit uint32
+	// pendingData is the overall data which have been received but not been
+	// consumed by applications.
+	pendingData uint32
+	// The amount of data the application has consumed but grpc has not sent
+	// window update for them. Used to reduce window update frequency.
+	pendingUpdate uint32
+	// delta is the extra window update given by receiver when an application
+	// is reading data bigger in size than the inFlow limit.
+	delta uint32
+}
+
+// newLimit updates the inflow window to a new value n.
+// It assumes that n is always greater than the old limit.
+func (f *inFlow) newLimit(n uint32) uint32 {
+	f.mu.Lock()
+	d := n - f.limit
+	f.limit = n
+	f.mu.Unlock()
+	return d
+}
+
+func (f *inFlow) maybeAdjust(n uint32) uint32 {
+	if n > uint32(math.MaxInt32) {
+		n = uint32(math.MaxInt32)
+	}
+	f.mu.Lock()
+	// estSenderQuota is the receiver's view of the maximum number of bytes the sender
+	// can send without a window update.
+	estSenderQuota := int32(f.limit - (f.pendingData + f.pendingUpdate))
+	// estUntransmittedData is the maximum number of bytes the sends might not have put
+	// on the wire yet. A value of 0 or less means that we have already received all or
+	// more bytes than the application is requesting to read.
+	estUntransmittedData := int32(n - f.pendingData) // Casting into int32 since it could be negative.
+	// This implies that unless we send a window update, the sender won't be able to send all the bytes
+	// for this message. Therefore we must send an update over the limit since there's an active read
+	// request from the application.
+	if estUntransmittedData > estSenderQuota {
+		// Sender's window shouldn't go more than 2^31 - 1 as specified in the HTTP spec.
+		if f.limit+n > maxWindowSize {
+			f.delta = maxWindowSize - f.limit
+		} else {
+			// Send a window update for the whole message and not just the difference between
+			// estUntransmittedData and estSenderQuota. This will be helpful in case the message
+			// is padded; We will fallback on the current available window(at least a 1/4th of the limit).
+			f.delta = n
+		}
+		f.mu.Unlock()
+		return f.delta
+	}
+	f.mu.Unlock()
+	return 0
+}
+
+// onData is invoked when some data frame is received. It updates pendingData.
+func (f *inFlow) onData(n uint32) error {
+	f.mu.Lock()
+	f.pendingData += n
+	if f.pendingData+f.pendingUpdate > f.limit+f.delta {
+		limit := f.limit
+		rcvd := f.pendingData + f.pendingUpdate
+		f.mu.Unlock()
+		return fmt.Errorf("received %d-bytes data exceeding the limit %d bytes", rcvd, limit)
+	}
+	f.mu.Unlock()
+	return nil
+}
+
+// onRead is invoked when the application reads the data. It returns the window size
+// to be sent to the peer.
+func (f *inFlow) onRead(n uint32) uint32 {
+	f.mu.Lock()
+	if f.pendingData == 0 {
+		f.mu.Unlock()
+		return 0
+	}
+	f.pendingData -= n
+	if n > f.delta {
+		n -= f.delta
+		f.delta = 0
+	} else {
+		f.delta -= n
+		n = 0
+	}
+	f.pendingUpdate += n
+	if f.pendingUpdate >= f.limit/4 {
+		wu := f.pendingUpdate
+		f.pendingUpdate = 0
+		f.mu.Unlock()
+		return wu
+	}
+	f.mu.Unlock()
+	return 0
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/go16.go b/go/vendor/google.golang.org/grpc/internal/transport/go16.go
new file mode 100644
index 0000000..e0d0011
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/go16.go
@@ -0,0 +1,52 @@
+// +build go1.6,!go1.7
+
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"net"
+	"net/http"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
+	"golang.org/x/net/context"
+)
+
+// dialContext connects to the address on the named network.
+func dialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	return (&net.Dialer{Cancel: ctx.Done()}).Dial(network, address)
+}
+
+// ContextErr converts the error from context package into a status error.
+func ContextErr(err error) error {
+	switch err {
+	case context.DeadlineExceeded:
+		return status.Error(codes.DeadlineExceeded, err.Error())
+	case context.Canceled:
+		return status.Error(codes.Canceled, err.Error())
+	}
+	return status.Errorf(codes.Internal, "Unexpected error from context packet: %v", err)
+}
+
+// contextFromRequest returns a background context.
+func contextFromRequest(r *http.Request) context.Context {
+	return context.Background()
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/go17.go b/go/vendor/google.golang.org/grpc/internal/transport/go17.go
new file mode 100644
index 0000000..4d515b0
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/go17.go
@@ -0,0 +1,53 @@
+// +build go1.7
+
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"context"
+	"net"
+	"net/http"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
+	netctx "golang.org/x/net/context"
+)
+
+// dialContext connects to the address on the named network.
+func dialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	return (&net.Dialer{}).DialContext(ctx, network, address)
+}
+
+// ContextErr converts the error from context package into a status error.
+func ContextErr(err error) error {
+	switch err {
+	case context.DeadlineExceeded, netctx.DeadlineExceeded:
+		return status.Error(codes.DeadlineExceeded, err.Error())
+	case context.Canceled, netctx.Canceled:
+		return status.Error(codes.Canceled, err.Error())
+	}
+	return status.Errorf(codes.Internal, "Unexpected error from context packet: %v", err)
+}
+
+// contextFromRequest returns a context from the HTTP Request.
+func contextFromRequest(r *http.Request) context.Context {
+	return r.Context()
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/handler_server.go b/go/vendor/google.golang.org/grpc/internal/transport/handler_server.go
new file mode 100644
index 0000000..c6fb4b9
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/handler_server.go
@@ -0,0 +1,449 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// This file is the implementation of a gRPC server using HTTP/2 which
+// uses the standard Go http2 Server implementation (via the
+// http.Handler interface), rather than speaking low-level HTTP/2
+// frames itself. It is the implementation of *grpc.Server.ServeHTTP.
+
+package transport
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/golang/protobuf/proto"
+	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+)
+
+// NewServerHandlerTransport returns a ServerTransport handling gRPC
+// from inside an http.Handler. It requires that the http Server
+// supports HTTP/2.
+func NewServerHandlerTransport(w http.ResponseWriter, r *http.Request, stats stats.Handler) (ServerTransport, error) {
+	if r.ProtoMajor != 2 {
+		return nil, errors.New("gRPC requires HTTP/2")
+	}
+	if r.Method != "POST" {
+		return nil, errors.New("invalid gRPC request method")
+	}
+	contentType := r.Header.Get("Content-Type")
+	// TODO: do we assume contentType is lowercase? we did before
+	contentSubtype, validContentType := contentSubtype(contentType)
+	if !validContentType {
+		return nil, errors.New("invalid gRPC request content-type")
+	}
+	if _, ok := w.(http.Flusher); !ok {
+		return nil, errors.New("gRPC requires a ResponseWriter supporting http.Flusher")
+	}
+	if _, ok := w.(http.CloseNotifier); !ok {
+		return nil, errors.New("gRPC requires a ResponseWriter supporting http.CloseNotifier")
+	}
+
+	st := &serverHandlerTransport{
+		rw:             w,
+		req:            r,
+		closedCh:       make(chan struct{}),
+		writes:         make(chan func()),
+		contentType:    contentType,
+		contentSubtype: contentSubtype,
+		stats:          stats,
+	}
+
+	if v := r.Header.Get("grpc-timeout"); v != "" {
+		to, err := decodeTimeout(v)
+		if err != nil {
+			return nil, status.Errorf(codes.Internal, "malformed time-out: %v", err)
+		}
+		st.timeoutSet = true
+		st.timeout = to
+	}
+
+	metakv := []string{"content-type", contentType}
+	if r.Host != "" {
+		metakv = append(metakv, ":authority", r.Host)
+	}
+	for k, vv := range r.Header {
+		k = strings.ToLower(k)
+		if isReservedHeader(k) && !isWhitelistedHeader(k) {
+			continue
+		}
+		for _, v := range vv {
+			v, err := decodeMetadataHeader(k, v)
+			if err != nil {
+				return nil, status.Errorf(codes.Internal, "malformed binary metadata: %v", err)
+			}
+			metakv = append(metakv, k, v)
+		}
+	}
+	st.headerMD = metadata.Pairs(metakv...)
+
+	return st, nil
+}
+
+// serverHandlerTransport is an implementation of ServerTransport
+// which replies to exactly one gRPC request (exactly one HTTP request),
+// using the net/http.Handler interface. This http.Handler is guaranteed
+// at this point to be speaking over HTTP/2, so it's able to speak valid
+// gRPC.
+type serverHandlerTransport struct {
+	rw               http.ResponseWriter
+	req              *http.Request
+	timeoutSet       bool
+	timeout          time.Duration
+	didCommonHeaders bool
+
+	headerMD metadata.MD
+
+	closeOnce sync.Once
+	closedCh  chan struct{} // closed on Close
+
+	// writes is a channel of code to run serialized in the
+	// ServeHTTP (HandleStreams) goroutine. The channel is closed
+	// when WriteStatus is called.
+	writes chan func()
+
+	// block concurrent WriteStatus calls
+	// e.g. grpc/(*serverStream).SendMsg/RecvMsg
+	writeStatusMu sync.Mutex
+
+	// we just mirror the request content-type
+	contentType string
+	// we store both contentType and contentSubtype so we don't keep recreating them
+	// TODO make sure this is consistent across handler_server and http2_server
+	contentSubtype string
+
+	stats stats.Handler
+}
+
+func (ht *serverHandlerTransport) Close() error {
+	ht.closeOnce.Do(ht.closeCloseChanOnce)
+	return nil
+}
+
+func (ht *serverHandlerTransport) closeCloseChanOnce() { close(ht.closedCh) }
+
+func (ht *serverHandlerTransport) RemoteAddr() net.Addr { return strAddr(ht.req.RemoteAddr) }
+
+// strAddr is a net.Addr backed by either a TCP "ip:port" string, or
+// the empty string if unknown.
+type strAddr string
+
+func (a strAddr) Network() string {
+	if a != "" {
+		// Per the documentation on net/http.Request.RemoteAddr, if this is
+		// set, it's set to the IP:port of the peer (hence, TCP):
+		// https://golang.org/pkg/net/http/#Request
+		//
+		// If we want to support Unix sockets later, we can
+		// add our own grpc-specific convention within the
+		// grpc codebase to set RemoteAddr to a different
+		// format, or probably better: we can attach it to the
+		// context and use that from serverHandlerTransport.RemoteAddr.
+		return "tcp"
+	}
+	return ""
+}
+
+func (a strAddr) String() string { return string(a) }
+
+// do runs fn in the ServeHTTP goroutine.
+func (ht *serverHandlerTransport) do(fn func()) error {
+	// Avoid a panic writing to closed channel. Imperfect but maybe good enough.
+	select {
+	case <-ht.closedCh:
+		return ErrConnClosing
+	default:
+		select {
+		case ht.writes <- fn:
+			return nil
+		case <-ht.closedCh:
+			return ErrConnClosing
+		}
+	}
+}
+
+func (ht *serverHandlerTransport) WriteStatus(s *Stream, st *status.Status) error {
+	ht.writeStatusMu.Lock()
+	defer ht.writeStatusMu.Unlock()
+
+	err := ht.do(func() {
+		ht.writeCommonHeaders(s)
+
+		// And flush, in case no header or body has been sent yet.
+		// This forces a separation of headers and trailers if this is the
+		// first call (for example, in end2end tests's TestNoService).
+		ht.rw.(http.Flusher).Flush()
+
+		h := ht.rw.Header()
+		h.Set("Grpc-Status", fmt.Sprintf("%d", st.Code()))
+		if m := st.Message(); m != "" {
+			h.Set("Grpc-Message", encodeGrpcMessage(m))
+		}
+
+		if p := st.Proto(); p != nil && len(p.Details) > 0 {
+			stBytes, err := proto.Marshal(p)
+			if err != nil {
+				// TODO: return error instead, when callers are able to handle it.
+				panic(err)
+			}
+
+			h.Set("Grpc-Status-Details-Bin", encodeBinHeader(stBytes))
+		}
+
+		if md := s.Trailer(); len(md) > 0 {
+			for k, vv := range md {
+				// Clients don't tolerate reading restricted headers after some non restricted ones were sent.
+				if isReservedHeader(k) {
+					continue
+				}
+				for _, v := range vv {
+					// http2 ResponseWriter mechanism to send undeclared Trailers after
+					// the headers have possibly been written.
+					h.Add(http2.TrailerPrefix+k, encodeMetadataHeader(k, v))
+				}
+			}
+		}
+	})
+
+	if err == nil { // transport has not been closed
+		if ht.stats != nil {
+			ht.stats.HandleRPC(s.Context(), &stats.OutTrailer{})
+		}
+		close(ht.writes)
+	}
+	ht.Close()
+	return err
+}
+
+// writeCommonHeaders sets common headers on the first write
+// call (Write, WriteHeader, or WriteStatus).
+func (ht *serverHandlerTransport) writeCommonHeaders(s *Stream) {
+	if ht.didCommonHeaders {
+		return
+	}
+	ht.didCommonHeaders = true
+
+	h := ht.rw.Header()
+	h["Date"] = nil // suppress Date to make tests happy; TODO: restore
+	h.Set("Content-Type", ht.contentType)
+
+	// Predeclare trailers we'll set later in WriteStatus (after the body).
+	// This is a SHOULD in the HTTP RFC, and the way you add (known)
+	// Trailers per the net/http.ResponseWriter contract.
+	// See https://golang.org/pkg/net/http/#ResponseWriter
+	// and https://golang.org/pkg/net/http/#example_ResponseWriter_trailers
+	h.Add("Trailer", "Grpc-Status")
+	h.Add("Trailer", "Grpc-Message")
+	h.Add("Trailer", "Grpc-Status-Details-Bin")
+
+	if s.sendCompress != "" {
+		h.Set("Grpc-Encoding", s.sendCompress)
+	}
+}
+
+func (ht *serverHandlerTransport) Write(s *Stream, hdr []byte, data []byte, opts *Options) error {
+	return ht.do(func() {
+		ht.writeCommonHeaders(s)
+		ht.rw.Write(hdr)
+		ht.rw.Write(data)
+		ht.rw.(http.Flusher).Flush()
+	})
+}
+
+func (ht *serverHandlerTransport) WriteHeader(s *Stream, md metadata.MD) error {
+	err := ht.do(func() {
+		ht.writeCommonHeaders(s)
+		h := ht.rw.Header()
+		for k, vv := range md {
+			// Clients don't tolerate reading restricted headers after some non restricted ones were sent.
+			if isReservedHeader(k) {
+				continue
+			}
+			for _, v := range vv {
+				v = encodeMetadataHeader(k, v)
+				h.Add(k, v)
+			}
+		}
+		ht.rw.WriteHeader(200)
+		ht.rw.(http.Flusher).Flush()
+	})
+
+	if err == nil {
+		if ht.stats != nil {
+			ht.stats.HandleRPC(s.Context(), &stats.OutHeader{})
+		}
+	}
+	return err
+}
+
+func (ht *serverHandlerTransport) HandleStreams(startStream func(*Stream), traceCtx func(context.Context, string) context.Context) {
+	// With this transport type there will be exactly 1 stream: this HTTP request.
+
+	ctx := contextFromRequest(ht.req)
+	var cancel context.CancelFunc
+	if ht.timeoutSet {
+		ctx, cancel = context.WithTimeout(ctx, ht.timeout)
+	} else {
+		ctx, cancel = context.WithCancel(ctx)
+	}
+
+	// requestOver is closed when either the request's context is done
+	// or the status has been written via WriteStatus.
+	requestOver := make(chan struct{})
+
+	// clientGone receives a single value if peer is gone, either
+	// because the underlying connection is dead or because the
+	// peer sends an http2 RST_STREAM.
+	clientGone := ht.rw.(http.CloseNotifier).CloseNotify()
+	go func() {
+		select {
+		case <-requestOver:
+		case <-ht.closedCh:
+		case <-clientGone:
+		}
+		cancel()
+		ht.Close()
+	}()
+
+	req := ht.req
+
+	s := &Stream{
+		id:             0, // irrelevant
+		requestRead:    func(int) {},
+		cancel:         cancel,
+		buf:            newRecvBuffer(),
+		st:             ht,
+		method:         req.URL.Path,
+		recvCompress:   req.Header.Get("grpc-encoding"),
+		contentSubtype: ht.contentSubtype,
+	}
+	pr := &peer.Peer{
+		Addr: ht.RemoteAddr(),
+	}
+	if req.TLS != nil {
+		pr.AuthInfo = credentials.TLSInfo{State: *req.TLS}
+	}
+	ctx = metadata.NewIncomingContext(ctx, ht.headerMD)
+	s.ctx = peer.NewContext(ctx, pr)
+	if ht.stats != nil {
+		s.ctx = ht.stats.TagRPC(s.ctx, &stats.RPCTagInfo{FullMethodName: s.method})
+		inHeader := &stats.InHeader{
+			FullMethod:  s.method,
+			RemoteAddr:  ht.RemoteAddr(),
+			Compression: s.recvCompress,
+		}
+		ht.stats.HandleRPC(s.ctx, inHeader)
+	}
+	s.trReader = &transportReader{
+		reader:        &recvBufferReader{ctx: s.ctx, ctxDone: s.ctx.Done(), recv: s.buf},
+		windowHandler: func(int) {},
+	}
+
+	// readerDone is closed when the Body.Read-ing goroutine exits.
+	readerDone := make(chan struct{})
+	go func() {
+		defer close(readerDone)
+
+		// TODO: minimize garbage, optimize recvBuffer code/ownership
+		const readSize = 8196
+		for buf := make([]byte, readSize); ; {
+			n, err := req.Body.Read(buf)
+			if n > 0 {
+				s.buf.put(recvMsg{data: buf[:n:n]})
+				buf = buf[n:]
+			}
+			if err != nil {
+				s.buf.put(recvMsg{err: mapRecvMsgError(err)})
+				return
+			}
+			if len(buf) == 0 {
+				buf = make([]byte, readSize)
+			}
+		}
+	}()
+
+	// startStream is provided by the *grpc.Server's serveStreams.
+	// It starts a goroutine serving s and exits immediately.
+	// The goroutine that is started is the one that then calls
+	// into ht, calling WriteHeader, Write, WriteStatus, Close, etc.
+	startStream(s)
+
+	ht.runStream()
+	close(requestOver)
+
+	// Wait for reading goroutine to finish.
+	req.Body.Close()
+	<-readerDone
+}
+
+func (ht *serverHandlerTransport) runStream() {
+	for {
+		select {
+		case fn, ok := <-ht.writes:
+			if !ok {
+				return
+			}
+			fn()
+		case <-ht.closedCh:
+			return
+		}
+	}
+}
+
+func (ht *serverHandlerTransport) IncrMsgSent() {}
+
+func (ht *serverHandlerTransport) IncrMsgRecv() {}
+
+func (ht *serverHandlerTransport) Drain() {
+	panic("Drain() is not implemented")
+}
+
+// mapRecvMsgError returns the non-nil err into the appropriate
+// error value as expected by callers of *grpc.parser.recvMsg.
+// In particular, in can only be:
+//   * io.EOF
+//   * io.ErrUnexpectedEOF
+//   * of type transport.ConnectionError
+//   * an error from the status package
+func mapRecvMsgError(err error) error {
+	if err == io.EOF || err == io.ErrUnexpectedEOF {
+		return err
+	}
+	if se, ok := err.(http2.StreamError); ok {
+		if code, ok := http2ErrConvTab[se.Code]; ok {
+			return status.Error(code, se.Error())
+		}
+	}
+	if strings.Contains(err.Error(), "body closed by handler") {
+		return status.Error(codes.Canceled, err.Error())
+	}
+	return connectionErrorf(true, err, err.Error())
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/http2_client.go b/go/vendor/google.golang.org/grpc/internal/transport/http2_client.go
new file mode 100644
index 0000000..0c3c47e
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/http2_client.go
@@ -0,0 +1,1368 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"io"
+	"math"
+	"net"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+)
+
+// http2Client implements the ClientTransport interface with HTTP2.
+type http2Client struct {
+	ctx        context.Context
+	cancel     context.CancelFunc
+	ctxDone    <-chan struct{} // Cache the ctx.Done() chan.
+	userAgent  string
+	md         interface{}
+	conn       net.Conn // underlying communication channel
+	loopy      *loopyWriter
+	remoteAddr net.Addr
+	localAddr  net.Addr
+	authInfo   credentials.AuthInfo // auth info about the connection
+
+	readerDone chan struct{} // sync point to enable testing.
+	writerDone chan struct{} // sync point to enable testing.
+	// goAway is closed to notify the upper layer (i.e., addrConn.transportMonitor)
+	// that the server sent GoAway on this transport.
+	goAway chan struct{}
+	// awakenKeepalive is used to wake up keepalive when after it has gone dormant.
+	awakenKeepalive chan struct{}
+
+	framer *framer
+	// controlBuf delivers all the control related tasks (e.g., window
+	// updates, reset streams, and various settings) to the controller.
+	controlBuf *controlBuffer
+	fc         *trInFlow
+	// The scheme used: https if TLS is on, http otherwise.
+	scheme string
+
+	isSecure bool
+
+	perRPCCreds []credentials.PerRPCCredentials
+
+	// Boolean to keep track of reading activity on transport.
+	// 1 is true and 0 is false.
+	activity         uint32 // Accessed atomically.
+	kp               keepalive.ClientParameters
+	keepaliveEnabled bool
+
+	statsHandler stats.Handler
+
+	initialWindowSize int32
+
+	// configured by peer through SETTINGS_MAX_HEADER_LIST_SIZE
+	maxSendHeaderListSize *uint32
+
+	bdpEst *bdpEstimator
+	// onSuccess is a callback that client transport calls upon
+	// receiving server preface to signal that a succefull HTTP2
+	// connection was established.
+	onSuccess func()
+
+	maxConcurrentStreams  uint32
+	streamQuota           int64
+	streamsQuotaAvailable chan struct{}
+	waitingStreams        uint32
+	nextID                uint32
+
+	mu            sync.Mutex // guard the following variables
+	state         transportState
+	activeStreams map[uint32]*Stream
+	// prevGoAway ID records the Last-Stream-ID in the previous GOAway frame.
+	prevGoAwayID uint32
+	// goAwayReason records the http2.ErrCode and debug data received with the
+	// GoAway frame.
+	goAwayReason GoAwayReason
+
+	// Fields below are for channelz metric collection.
+	channelzID int64 // channelz unique identification number
+	czData     *channelzData
+
+	onGoAway func(GoAwayReason)
+	onClose  func()
+}
+
+func dial(ctx context.Context, fn func(context.Context, string) (net.Conn, error), addr string) (net.Conn, error) {
+	if fn != nil {
+		return fn(ctx, addr)
+	}
+	return dialContext(ctx, "tcp", addr)
+}
+
+func isTemporary(err error) bool {
+	switch err := err.(type) {
+	case interface {
+		Temporary() bool
+	}:
+		return err.Temporary()
+	case interface {
+		Timeout() bool
+	}:
+		// Timeouts may be resolved upon retry, and are thus treated as
+		// temporary.
+		return err.Timeout()
+	}
+	return true
+}
+
+// newHTTP2Client constructs a connected ClientTransport to addr based on HTTP2
+// and starts to receive messages on it. Non-nil error returns if construction
+// fails.
+func newHTTP2Client(connectCtx, ctx context.Context, addr TargetInfo, opts ConnectOptions, onSuccess func(), onGoAway func(GoAwayReason), onClose func()) (_ *http2Client, err error) {
+	scheme := "http"
+	ctx, cancel := context.WithCancel(ctx)
+	defer func() {
+		if err != nil {
+			cancel()
+		}
+	}()
+
+	conn, err := dial(connectCtx, opts.Dialer, addr.Addr)
+	if err != nil {
+		if opts.FailOnNonTempDialError {
+			return nil, connectionErrorf(isTemporary(err), err, "transport: error while dialing: %v", err)
+		}
+		return nil, connectionErrorf(true, err, "transport: Error while dialing %v", err)
+	}
+	// Any further errors will close the underlying connection
+	defer func(conn net.Conn) {
+		if err != nil {
+			conn.Close()
+		}
+	}(conn)
+	var (
+		isSecure bool
+		authInfo credentials.AuthInfo
+	)
+	transportCreds := opts.TransportCredentials
+	perRPCCreds := opts.PerRPCCredentials
+
+	if b := opts.CredsBundle; b != nil {
+		if t := b.TransportCredentials(); t != nil {
+			transportCreds = t
+		}
+		if t := b.PerRPCCredentials(); t != nil {
+			perRPCCreds = append(perRPCCreds, t)
+		}
+	}
+	if transportCreds != nil {
+		scheme = "https"
+		conn, authInfo, err = transportCreds.ClientHandshake(connectCtx, addr.Authority, conn)
+		if err != nil {
+			return nil, connectionErrorf(isTemporary(err), err, "transport: authentication handshake failed: %v", err)
+		}
+		isSecure = true
+	}
+	kp := opts.KeepaliveParams
+	// Validate keepalive parameters.
+	if kp.Time == 0 {
+		kp.Time = defaultClientKeepaliveTime
+	}
+	if kp.Timeout == 0 {
+		kp.Timeout = defaultClientKeepaliveTimeout
+	}
+	dynamicWindow := true
+	icwz := int32(initialWindowSize)
+	if opts.InitialConnWindowSize >= defaultWindowSize {
+		icwz = opts.InitialConnWindowSize
+		dynamicWindow = false
+	}
+	writeBufSize := opts.WriteBufferSize
+	readBufSize := opts.ReadBufferSize
+	maxHeaderListSize := defaultClientMaxHeaderListSize
+	if opts.MaxHeaderListSize != nil {
+		maxHeaderListSize = *opts.MaxHeaderListSize
+	}
+	t := &http2Client{
+		ctx:                   ctx,
+		ctxDone:               ctx.Done(), // Cache Done chan.
+		cancel:                cancel,
+		userAgent:             opts.UserAgent,
+		md:                    addr.Metadata,
+		conn:                  conn,
+		remoteAddr:            conn.RemoteAddr(),
+		localAddr:             conn.LocalAddr(),
+		authInfo:              authInfo,
+		readerDone:            make(chan struct{}),
+		writerDone:            make(chan struct{}),
+		goAway:                make(chan struct{}),
+		awakenKeepalive:       make(chan struct{}, 1),
+		framer:                newFramer(conn, writeBufSize, readBufSize, maxHeaderListSize),
+		fc:                    &trInFlow{limit: uint32(icwz)},
+		scheme:                scheme,
+		activeStreams:         make(map[uint32]*Stream),
+		isSecure:              isSecure,
+		perRPCCreds:           perRPCCreds,
+		kp:                    kp,
+		statsHandler:          opts.StatsHandler,
+		initialWindowSize:     initialWindowSize,
+		onSuccess:             onSuccess,
+		nextID:                1,
+		maxConcurrentStreams:  defaultMaxStreamsClient,
+		streamQuota:           defaultMaxStreamsClient,
+		streamsQuotaAvailable: make(chan struct{}, 1),
+		czData:                new(channelzData),
+		onGoAway:              onGoAway,
+		onClose:               onClose,
+	}
+	t.controlBuf = newControlBuffer(t.ctxDone)
+	if opts.InitialWindowSize >= defaultWindowSize {
+		t.initialWindowSize = opts.InitialWindowSize
+		dynamicWindow = false
+	}
+	if dynamicWindow {
+		t.bdpEst = &bdpEstimator{
+			bdp:               initialWindowSize,
+			updateFlowControl: t.updateFlowControl,
+		}
+	}
+	// Make sure awakenKeepalive can't be written upon.
+	// keepalive routine will make it writable, if need be.
+	t.awakenKeepalive <- struct{}{}
+	if t.statsHandler != nil {
+		t.ctx = t.statsHandler.TagConn(t.ctx, &stats.ConnTagInfo{
+			RemoteAddr: t.remoteAddr,
+			LocalAddr:  t.localAddr,
+		})
+		connBegin := &stats.ConnBegin{
+			Client: true,
+		}
+		t.statsHandler.HandleConn(t.ctx, connBegin)
+	}
+	if channelz.IsOn() {
+		t.channelzID = channelz.RegisterNormalSocket(t, opts.ChannelzParentID, "")
+	}
+	if t.kp.Time != infinity {
+		t.keepaliveEnabled = true
+		go t.keepalive()
+	}
+	// Start the reader goroutine for incoming message. Each transport has
+	// a dedicated goroutine which reads HTTP2 frame from network. Then it
+	// dispatches the frame to the corresponding stream entity.
+	go t.reader()
+
+	// Send connection preface to server.
+	n, err := t.conn.Write(clientPreface)
+	if err != nil {
+		t.Close()
+		return nil, connectionErrorf(true, err, "transport: failed to write client preface: %v", err)
+	}
+	if n != len(clientPreface) {
+		t.Close()
+		return nil, connectionErrorf(true, err, "transport: preface mismatch, wrote %d bytes; want %d", n, len(clientPreface))
+	}
+	var ss []http2.Setting
+
+	if t.initialWindowSize != defaultWindowSize {
+		ss = append(ss, http2.Setting{
+			ID:  http2.SettingInitialWindowSize,
+			Val: uint32(t.initialWindowSize),
+		})
+	}
+	if opts.MaxHeaderListSize != nil {
+		ss = append(ss, http2.Setting{
+			ID:  http2.SettingMaxHeaderListSize,
+			Val: *opts.MaxHeaderListSize,
+		})
+	}
+	err = t.framer.fr.WriteSettings(ss...)
+	if err != nil {
+		t.Close()
+		return nil, connectionErrorf(true, err, "transport: failed to write initial settings frame: %v", err)
+	}
+	// Adjust the connection flow control window if needed.
+	if delta := uint32(icwz - defaultWindowSize); delta > 0 {
+		if err := t.framer.fr.WriteWindowUpdate(0, delta); err != nil {
+			t.Close()
+			return nil, connectionErrorf(true, err, "transport: failed to write window update: %v", err)
+		}
+	}
+
+	t.framer.writer.Flush()
+	go func() {
+		t.loopy = newLoopyWriter(clientSide, t.framer, t.controlBuf, t.bdpEst)
+		err := t.loopy.run()
+		if err != nil {
+			errorf("transport: loopyWriter.run returning. Err: %v", err)
+		}
+		// If it's a connection error, let reader goroutine handle it
+		// since there might be data in the buffers.
+		if _, ok := err.(net.Error); !ok {
+			t.conn.Close()
+		}
+		close(t.writerDone)
+	}()
+	return t, nil
+}
+
+func (t *http2Client) newStream(ctx context.Context, callHdr *CallHdr) *Stream {
+	// TODO(zhaoq): Handle uint32 overflow of Stream.id.
+	s := &Stream{
+		done:           make(chan struct{}),
+		method:         callHdr.Method,
+		sendCompress:   callHdr.SendCompress,
+		buf:            newRecvBuffer(),
+		headerChan:     make(chan struct{}),
+		contentSubtype: callHdr.ContentSubtype,
+	}
+	s.wq = newWriteQuota(defaultWriteQuota, s.done)
+	s.requestRead = func(n int) {
+		t.adjustWindow(s, uint32(n))
+	}
+	// The client side stream context should have exactly the same life cycle with the user provided context.
+	// That means, s.ctx should be read-only. And s.ctx is done iff ctx is done.
+	// So we use the original context here instead of creating a copy.
+	s.ctx = ctx
+	s.trReader = &transportReader{
+		reader: &recvBufferReader{
+			ctx:     s.ctx,
+			ctxDone: s.ctx.Done(),
+			recv:    s.buf,
+		},
+		windowHandler: func(n int) {
+			t.updateWindow(s, uint32(n))
+		},
+	}
+	return s
+}
+
+func (t *http2Client) getPeer() *peer.Peer {
+	pr := &peer.Peer{
+		Addr: t.remoteAddr,
+	}
+	// Attach Auth info if there is any.
+	if t.authInfo != nil {
+		pr.AuthInfo = t.authInfo
+	}
+	return pr
+}
+
+func (t *http2Client) createHeaderFields(ctx context.Context, callHdr *CallHdr) ([]hpack.HeaderField, error) {
+	aud := t.createAudience(callHdr)
+	authData, err := t.getTrAuthData(ctx, aud)
+	if err != nil {
+		return nil, err
+	}
+	callAuthData, err := t.getCallAuthData(ctx, aud, callHdr)
+	if err != nil {
+		return nil, err
+	}
+	// TODO(mmukhi): Benchmark if the performance gets better if count the metadata and other header fields
+	// first and create a slice of that exact size.
+	// Make the slice of certain predictable size to reduce allocations made by append.
+	hfLen := 7 // :method, :scheme, :path, :authority, content-type, user-agent, te
+	hfLen += len(authData) + len(callAuthData)
+	headerFields := make([]hpack.HeaderField, 0, hfLen)
+	headerFields = append(headerFields, hpack.HeaderField{Name: ":method", Value: "POST"})
+	headerFields = append(headerFields, hpack.HeaderField{Name: ":scheme", Value: t.scheme})
+	headerFields = append(headerFields, hpack.HeaderField{Name: ":path", Value: callHdr.Method})
+	headerFields = append(headerFields, hpack.HeaderField{Name: ":authority", Value: callHdr.Host})
+	headerFields = append(headerFields, hpack.HeaderField{Name: "content-type", Value: contentType(callHdr.ContentSubtype)})
+	headerFields = append(headerFields, hpack.HeaderField{Name: "user-agent", Value: t.userAgent})
+	headerFields = append(headerFields, hpack.HeaderField{Name: "te", Value: "trailers"})
+	if callHdr.PreviousAttempts > 0 {
+		headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-previous-rpc-attempts", Value: strconv.Itoa(callHdr.PreviousAttempts)})
+	}
+
+	if callHdr.SendCompress != "" {
+		headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-encoding", Value: callHdr.SendCompress})
+	}
+	if dl, ok := ctx.Deadline(); ok {
+		// Send out timeout regardless its value. The server can detect timeout context by itself.
+		// TODO(mmukhi): Perhaps this field should be updated when actually writing out to the wire.
+		timeout := dl.Sub(time.Now())
+		headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-timeout", Value: encodeTimeout(timeout)})
+	}
+	for k, v := range authData {
+		headerFields = append(headerFields, hpack.HeaderField{Name: k, Value: encodeMetadataHeader(k, v)})
+	}
+	for k, v := range callAuthData {
+		headerFields = append(headerFields, hpack.HeaderField{Name: k, Value: encodeMetadataHeader(k, v)})
+	}
+	if b := stats.OutgoingTags(ctx); b != nil {
+		headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-tags-bin", Value: encodeBinHeader(b)})
+	}
+	if b := stats.OutgoingTrace(ctx); b != nil {
+		headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-trace-bin", Value: encodeBinHeader(b)})
+	}
+
+	if md, added, ok := metadata.FromOutgoingContextRaw(ctx); ok {
+		var k string
+		for _, vv := range added {
+			for i, v := range vv {
+				if i%2 == 0 {
+					k = v
+					continue
+				}
+				// HTTP doesn't allow you to set pseudoheaders after non pseudoheaders were set.
+				if isReservedHeader(k) {
+					continue
+				}
+				headerFields = append(headerFields, hpack.HeaderField{Name: strings.ToLower(k), Value: encodeMetadataHeader(k, v)})
+			}
+		}
+		for k, vv := range md {
+			// HTTP doesn't allow you to set pseudoheaders after non pseudoheaders were set.
+			if isReservedHeader(k) {
+				continue
+			}
+			for _, v := range vv {
+				headerFields = append(headerFields, hpack.HeaderField{Name: k, Value: encodeMetadataHeader(k, v)})
+			}
+		}
+	}
+	if md, ok := t.md.(*metadata.MD); ok {
+		for k, vv := range *md {
+			if isReservedHeader(k) {
+				continue
+			}
+			for _, v := range vv {
+				headerFields = append(headerFields, hpack.HeaderField{Name: k, Value: encodeMetadataHeader(k, v)})
+			}
+		}
+	}
+	return headerFields, nil
+}
+
+func (t *http2Client) createAudience(callHdr *CallHdr) string {
+	// Create an audience string only if needed.
+	if len(t.perRPCCreds) == 0 && callHdr.Creds == nil {
+		return ""
+	}
+	// Construct URI required to get auth request metadata.
+	// Omit port if it is the default one.
+	host := strings.TrimSuffix(callHdr.Host, ":443")
+	pos := strings.LastIndex(callHdr.Method, "/")
+	if pos == -1 {
+		pos = len(callHdr.Method)
+	}
+	return "https://" + host + callHdr.Method[:pos]
+}
+
+func (t *http2Client) getTrAuthData(ctx context.Context, audience string) (map[string]string, error) {
+	authData := map[string]string{}
+	for _, c := range t.perRPCCreds {
+		data, err := c.GetRequestMetadata(ctx, audience)
+		if err != nil {
+			if _, ok := status.FromError(err); ok {
+				return nil, err
+			}
+
+			return nil, status.Errorf(codes.Unauthenticated, "transport: %v", err)
+		}
+		for k, v := range data {
+			// Capital header names are illegal in HTTP/2.
+			k = strings.ToLower(k)
+			authData[k] = v
+		}
+	}
+	return authData, nil
+}
+
+func (t *http2Client) getCallAuthData(ctx context.Context, audience string, callHdr *CallHdr) (map[string]string, error) {
+	callAuthData := map[string]string{}
+	// Check if credentials.PerRPCCredentials were provided via call options.
+	// Note: if these credentials are provided both via dial options and call
+	// options, then both sets of credentials will be applied.
+	if callCreds := callHdr.Creds; callCreds != nil {
+		if !t.isSecure && callCreds.RequireTransportSecurity() {
+			return nil, status.Error(codes.Unauthenticated, "transport: cannot send secure credentials on an insecure connection")
+		}
+		data, err := callCreds.GetRequestMetadata(ctx, audience)
+		if err != nil {
+			return nil, status.Errorf(codes.Internal, "transport: %v", err)
+		}
+		for k, v := range data {
+			// Capital header names are illegal in HTTP/2
+			k = strings.ToLower(k)
+			callAuthData[k] = v
+		}
+	}
+	return callAuthData, nil
+}
+
+// NewStream creates a stream and registers it into the transport as "active"
+// streams.
+func (t *http2Client) NewStream(ctx context.Context, callHdr *CallHdr) (_ *Stream, err error) {
+	ctx = peer.NewContext(ctx, t.getPeer())
+	headerFields, err := t.createHeaderFields(ctx, callHdr)
+	if err != nil {
+		return nil, err
+	}
+	s := t.newStream(ctx, callHdr)
+	cleanup := func(err error) {
+		if s.swapState(streamDone) == streamDone {
+			// If it was already done, return.
+			return
+		}
+		// The stream was unprocessed by the server.
+		atomic.StoreUint32(&s.unprocessed, 1)
+		s.write(recvMsg{err: err})
+		close(s.done)
+		// If headerChan isn't closed, then close it.
+		if atomic.SwapUint32(&s.headerDone, 1) == 0 {
+			close(s.headerChan)
+		}
+
+	}
+	hdr := &headerFrame{
+		hf:        headerFields,
+		endStream: false,
+		initStream: func(id uint32) (bool, error) {
+			t.mu.Lock()
+			if state := t.state; state != reachable {
+				t.mu.Unlock()
+				// Do a quick cleanup.
+				err := error(errStreamDrain)
+				if state == closing {
+					err = ErrConnClosing
+				}
+				cleanup(err)
+				return false, err
+			}
+			t.activeStreams[id] = s
+			if channelz.IsOn() {
+				atomic.AddInt64(&t.czData.streamsStarted, 1)
+				atomic.StoreInt64(&t.czData.lastStreamCreatedTime, time.Now().UnixNano())
+			}
+			var sendPing bool
+			// If the number of active streams change from 0 to 1, then check if keepalive
+			// has gone dormant. If so, wake it up.
+			if len(t.activeStreams) == 1 && t.keepaliveEnabled {
+				select {
+				case t.awakenKeepalive <- struct{}{}:
+					sendPing = true
+					// Fill the awakenKeepalive channel again as this channel must be
+					// kept non-writable except at the point that the keepalive()
+					// goroutine is waiting either to be awaken or shutdown.
+					t.awakenKeepalive <- struct{}{}
+				default:
+				}
+			}
+			t.mu.Unlock()
+			return sendPing, nil
+		},
+		onOrphaned: cleanup,
+		wq:         s.wq,
+	}
+	firstTry := true
+	var ch chan struct{}
+	checkForStreamQuota := func(it interface{}) bool {
+		if t.streamQuota <= 0 { // Can go negative if server decreases it.
+			if firstTry {
+				t.waitingStreams++
+			}
+			ch = t.streamsQuotaAvailable
+			return false
+		}
+		if !firstTry {
+			t.waitingStreams--
+		}
+		t.streamQuota--
+		h := it.(*headerFrame)
+		h.streamID = t.nextID
+		t.nextID += 2
+		s.id = h.streamID
+		s.fc = &inFlow{limit: uint32(t.initialWindowSize)}
+		if t.streamQuota > 0 && t.waitingStreams > 0 {
+			select {
+			case t.streamsQuotaAvailable <- struct{}{}:
+			default:
+			}
+		}
+		return true
+	}
+	var hdrListSizeErr error
+	checkForHeaderListSize := func(it interface{}) bool {
+		if t.maxSendHeaderListSize == nil {
+			return true
+		}
+		hdrFrame := it.(*headerFrame)
+		var sz int64
+		for _, f := range hdrFrame.hf {
+			if sz += int64(f.Size()); sz > int64(*t.maxSendHeaderListSize) {
+				hdrListSizeErr = status.Errorf(codes.Internal, "header list size to send violates the maximum size (%d bytes) set by server", *t.maxSendHeaderListSize)
+				return false
+			}
+		}
+		return true
+	}
+	for {
+		success, err := t.controlBuf.executeAndPut(func(it interface{}) bool {
+			if !checkForStreamQuota(it) {
+				return false
+			}
+			if !checkForHeaderListSize(it) {
+				return false
+			}
+			return true
+		}, hdr)
+		if err != nil {
+			return nil, err
+		}
+		if success {
+			break
+		}
+		if hdrListSizeErr != nil {
+			return nil, hdrListSizeErr
+		}
+		firstTry = false
+		select {
+		case <-ch:
+		case <-s.ctx.Done():
+			return nil, ContextErr(s.ctx.Err())
+		case <-t.goAway:
+			return nil, errStreamDrain
+		case <-t.ctx.Done():
+			return nil, ErrConnClosing
+		}
+	}
+	if t.statsHandler != nil {
+		outHeader := &stats.OutHeader{
+			Client:      true,
+			FullMethod:  callHdr.Method,
+			RemoteAddr:  t.remoteAddr,
+			LocalAddr:   t.localAddr,
+			Compression: callHdr.SendCompress,
+		}
+		t.statsHandler.HandleRPC(s.ctx, outHeader)
+	}
+	return s, nil
+}
+
+// CloseStream clears the footprint of a stream when the stream is not needed any more.
+// This must not be executed in reader's goroutine.
+func (t *http2Client) CloseStream(s *Stream, err error) {
+	var (
+		rst     bool
+		rstCode http2.ErrCode
+	)
+	if err != nil {
+		rst = true
+		rstCode = http2.ErrCodeCancel
+	}
+	t.closeStream(s, err, rst, rstCode, status.Convert(err), nil, false)
+}
+
+func (t *http2Client) closeStream(s *Stream, err error, rst bool, rstCode http2.ErrCode, st *status.Status, mdata map[string][]string, eosReceived bool) {
+	// Set stream status to done.
+	if s.swapState(streamDone) == streamDone {
+		// If it was already done, return.  If multiple closeStream calls
+		// happen simultaneously, wait for the first to finish.
+		<-s.done
+		return
+	}
+	// status and trailers can be updated here without any synchronization because the stream goroutine will
+	// only read it after it sees an io.EOF error from read or write and we'll write those errors
+	// only after updating this.
+	s.status = st
+	if len(mdata) > 0 {
+		s.trailer = mdata
+	}
+	if err != nil {
+		// This will unblock reads eventually.
+		s.write(recvMsg{err: err})
+	}
+	// If headerChan isn't closed, then close it.
+	if atomic.SwapUint32(&s.headerDone, 1) == 0 {
+		s.noHeaders = true
+		close(s.headerChan)
+	}
+	cleanup := &cleanupStream{
+		streamID: s.id,
+		onWrite: func() {
+			t.mu.Lock()
+			if t.activeStreams != nil {
+				delete(t.activeStreams, s.id)
+			}
+			t.mu.Unlock()
+			if channelz.IsOn() {
+				if eosReceived {
+					atomic.AddInt64(&t.czData.streamsSucceeded, 1)
+				} else {
+					atomic.AddInt64(&t.czData.streamsFailed, 1)
+				}
+			}
+		},
+		rst:     rst,
+		rstCode: rstCode,
+	}
+	addBackStreamQuota := func(interface{}) bool {
+		t.streamQuota++
+		if t.streamQuota > 0 && t.waitingStreams > 0 {
+			select {
+			case t.streamsQuotaAvailable <- struct{}{}:
+			default:
+			}
+		}
+		return true
+	}
+	t.controlBuf.executeAndPut(addBackStreamQuota, cleanup)
+	// This will unblock write.
+	close(s.done)
+}
+
+// Close kicks off the shutdown process of the transport. This should be called
+// only once on a transport. Once it is called, the transport should not be
+// accessed any more.
+//
+// This method blocks until the addrConn that initiated this transport is
+// re-connected. This happens because t.onClose() begins reconnect logic at the
+// addrConn level and blocks until the addrConn is successfully connected.
+func (t *http2Client) Close() error {
+	t.mu.Lock()
+	// Make sure we only Close once.
+	if t.state == closing {
+		t.mu.Unlock()
+		return nil
+	}
+	t.state = closing
+	streams := t.activeStreams
+	t.activeStreams = nil
+	t.mu.Unlock()
+	t.controlBuf.finish()
+	t.cancel()
+	err := t.conn.Close()
+	if channelz.IsOn() {
+		channelz.RemoveEntry(t.channelzID)
+	}
+	// Notify all active streams.
+	for _, s := range streams {
+		t.closeStream(s, ErrConnClosing, false, http2.ErrCodeNo, status.New(codes.Unavailable, ErrConnClosing.Desc), nil, false)
+	}
+	if t.statsHandler != nil {
+		connEnd := &stats.ConnEnd{
+			Client: true,
+		}
+		t.statsHandler.HandleConn(t.ctx, connEnd)
+	}
+	go t.onClose()
+	return err
+}
+
+// GracefulClose sets the state to draining, which prevents new streams from
+// being created and causes the transport to be closed when the last active
+// stream is closed.  If there are no active streams, the transport is closed
+// immediately.  This does nothing if the transport is already draining or
+// closing.
+func (t *http2Client) GracefulClose() error {
+	t.mu.Lock()
+	// Make sure we move to draining only from active.
+	if t.state == draining || t.state == closing {
+		t.mu.Unlock()
+		return nil
+	}
+	t.state = draining
+	active := len(t.activeStreams)
+	t.mu.Unlock()
+	if active == 0 {
+		return t.Close()
+	}
+	t.controlBuf.put(&incomingGoAway{})
+	return nil
+}
+
+// Write formats the data into HTTP2 data frame(s) and sends it out. The caller
+// should proceed only if Write returns nil.
+func (t *http2Client) Write(s *Stream, hdr []byte, data []byte, opts *Options) error {
+	if opts.Last {
+		// If it's the last message, update stream state.
+		if !s.compareAndSwapState(streamActive, streamWriteDone) {
+			return errStreamDone
+		}
+	} else if s.getState() != streamActive {
+		return errStreamDone
+	}
+	df := &dataFrame{
+		streamID:  s.id,
+		endStream: opts.Last,
+	}
+	if hdr != nil || data != nil { // If it's not an empty data frame.
+		// Add some data to grpc message header so that we can equally
+		// distribute bytes across frames.
+		emptyLen := http2MaxFrameLen - len(hdr)
+		if emptyLen > len(data) {
+			emptyLen = len(data)
+		}
+		hdr = append(hdr, data[:emptyLen]...)
+		data = data[emptyLen:]
+		df.h, df.d = hdr, data
+		// TODO(mmukhi): The above logic in this if can be moved to loopyWriter's data handler.
+		if err := s.wq.get(int32(len(hdr) + len(data))); err != nil {
+			return err
+		}
+	}
+	return t.controlBuf.put(df)
+}
+
+func (t *http2Client) getStream(f http2.Frame) (*Stream, bool) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	s, ok := t.activeStreams[f.Header().StreamID]
+	return s, ok
+}
+
+// adjustWindow sends out extra window update over the initial window size
+// of stream if the application is requesting data larger in size than
+// the window.
+func (t *http2Client) adjustWindow(s *Stream, n uint32) {
+	if w := s.fc.maybeAdjust(n); w > 0 {
+		t.controlBuf.put(&outgoingWindowUpdate{streamID: s.id, increment: w})
+	}
+}
+
+// updateWindow adjusts the inbound quota for the stream.
+// Window updates will be sent out when the cumulative quota
+// exceeds the corresponding threshold.
+func (t *http2Client) updateWindow(s *Stream, n uint32) {
+	if w := s.fc.onRead(n); w > 0 {
+		t.controlBuf.put(&outgoingWindowUpdate{streamID: s.id, increment: w})
+	}
+}
+
+// updateFlowControl updates the incoming flow control windows
+// for the transport and the stream based on the current bdp
+// estimation.
+func (t *http2Client) updateFlowControl(n uint32) {
+	t.mu.Lock()
+	for _, s := range t.activeStreams {
+		s.fc.newLimit(n)
+	}
+	t.mu.Unlock()
+	updateIWS := func(interface{}) bool {
+		t.initialWindowSize = int32(n)
+		return true
+	}
+	t.controlBuf.executeAndPut(updateIWS, &outgoingWindowUpdate{streamID: 0, increment: t.fc.newLimit(n)})
+	t.controlBuf.put(&outgoingSettings{
+		ss: []http2.Setting{
+			{
+				ID:  http2.SettingInitialWindowSize,
+				Val: n,
+			},
+		},
+	})
+}
+
+func (t *http2Client) handleData(f *http2.DataFrame) {
+	size := f.Header().Length
+	var sendBDPPing bool
+	if t.bdpEst != nil {
+		sendBDPPing = t.bdpEst.add(size)
+	}
+	// Decouple connection's flow control from application's read.
+	// An update on connection's flow control should not depend on
+	// whether user application has read the data or not. Such a
+	// restriction is already imposed on the stream's flow control,
+	// and therefore the sender will be blocked anyways.
+	// Decoupling the connection flow control will prevent other
+	// active(fast) streams from starving in presence of slow or
+	// inactive streams.
+	//
+	if w := t.fc.onData(size); w > 0 {
+		t.controlBuf.put(&outgoingWindowUpdate{
+			streamID:  0,
+			increment: w,
+		})
+	}
+	if sendBDPPing {
+		// Avoid excessive ping detection (e.g. in an L7 proxy)
+		// by sending a window update prior to the BDP ping.
+
+		if w := t.fc.reset(); w > 0 {
+			t.controlBuf.put(&outgoingWindowUpdate{
+				streamID:  0,
+				increment: w,
+			})
+		}
+
+		t.controlBuf.put(bdpPing)
+	}
+	// Select the right stream to dispatch.
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	if size > 0 {
+		if err := s.fc.onData(size); err != nil {
+			t.closeStream(s, io.EOF, true, http2.ErrCodeFlowControl, status.New(codes.Internal, err.Error()), nil, false)
+			return
+		}
+		if f.Header().Flags.Has(http2.FlagDataPadded) {
+			if w := s.fc.onRead(size - uint32(len(f.Data()))); w > 0 {
+				t.controlBuf.put(&outgoingWindowUpdate{s.id, w})
+			}
+		}
+		// TODO(bradfitz, zhaoq): A copy is required here because there is no
+		// guarantee f.Data() is consumed before the arrival of next frame.
+		// Can this copy be eliminated?
+		if len(f.Data()) > 0 {
+			data := make([]byte, len(f.Data()))
+			copy(data, f.Data())
+			s.write(recvMsg{data: data})
+		}
+	}
+	// The server has closed the stream without sending trailers.  Record that
+	// the read direction is closed, and set the status appropriately.
+	if f.FrameHeader.Flags.Has(http2.FlagDataEndStream) {
+		t.closeStream(s, io.EOF, false, http2.ErrCodeNo, status.New(codes.Internal, "server closed the stream without sending trailers"), nil, true)
+	}
+}
+
+func (t *http2Client) handleRSTStream(f *http2.RSTStreamFrame) {
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	if f.ErrCode == http2.ErrCodeRefusedStream {
+		// The stream was unprocessed by the server.
+		atomic.StoreUint32(&s.unprocessed, 1)
+	}
+	statusCode, ok := http2ErrConvTab[f.ErrCode]
+	if !ok {
+		warningf("transport: http2Client.handleRSTStream found no mapped gRPC status for the received http2 error %v", f.ErrCode)
+		statusCode = codes.Unknown
+	}
+	if statusCode == codes.Canceled {
+		// Our deadline was already exceeded, and that was likely the cause of
+		// this cancelation.  Alter the status code accordingly.
+		if d, ok := s.ctx.Deadline(); ok && d.After(time.Now()) {
+			statusCode = codes.DeadlineExceeded
+		}
+	}
+	t.closeStream(s, io.EOF, false, http2.ErrCodeNo, status.Newf(statusCode, "stream terminated by RST_STREAM with error code: %v", f.ErrCode), nil, false)
+}
+
+func (t *http2Client) handleSettings(f *http2.SettingsFrame, isFirst bool) {
+	if f.IsAck() {
+		return
+	}
+	var maxStreams *uint32
+	var ss []http2.Setting
+	var updateFuncs []func()
+	f.ForeachSetting(func(s http2.Setting) error {
+		switch s.ID {
+		case http2.SettingMaxConcurrentStreams:
+			maxStreams = new(uint32)
+			*maxStreams = s.Val
+		case http2.SettingMaxHeaderListSize:
+			updateFuncs = append(updateFuncs, func() {
+				t.maxSendHeaderListSize = new(uint32)
+				*t.maxSendHeaderListSize = s.Val
+			})
+		default:
+			ss = append(ss, s)
+		}
+		return nil
+	})
+	if isFirst && maxStreams == nil {
+		maxStreams = new(uint32)
+		*maxStreams = math.MaxUint32
+	}
+	sf := &incomingSettings{
+		ss: ss,
+	}
+	if maxStreams != nil {
+		updateStreamQuota := func() {
+			delta := int64(*maxStreams) - int64(t.maxConcurrentStreams)
+			t.maxConcurrentStreams = *maxStreams
+			t.streamQuota += delta
+			if delta > 0 && t.waitingStreams > 0 {
+				close(t.streamsQuotaAvailable) // wake all of them up.
+				t.streamsQuotaAvailable = make(chan struct{}, 1)
+			}
+		}
+		updateFuncs = append(updateFuncs, updateStreamQuota)
+	}
+	t.controlBuf.executeAndPut(func(interface{}) bool {
+		for _, f := range updateFuncs {
+			f()
+		}
+		return true
+	}, sf)
+}
+
+func (t *http2Client) handlePing(f *http2.PingFrame) {
+	if f.IsAck() {
+		// Maybe it's a BDP ping.
+		if t.bdpEst != nil {
+			t.bdpEst.calculate(f.Data)
+		}
+		return
+	}
+	pingAck := &ping{ack: true}
+	copy(pingAck.data[:], f.Data[:])
+	t.controlBuf.put(pingAck)
+}
+
+func (t *http2Client) handleGoAway(f *http2.GoAwayFrame) {
+	t.mu.Lock()
+	if t.state == closing {
+		t.mu.Unlock()
+		return
+	}
+	if f.ErrCode == http2.ErrCodeEnhanceYourCalm {
+		infof("Client received GoAway with http2.ErrCodeEnhanceYourCalm.")
+	}
+	id := f.LastStreamID
+	if id > 0 && id%2 != 1 {
+		t.mu.Unlock()
+		t.Close()
+		return
+	}
+	// A client can receive multiple GoAways from the server (see
+	// https://github.com/grpc/grpc-go/issues/1387).  The idea is that the first
+	// GoAway will be sent with an ID of MaxInt32 and the second GoAway will be
+	// sent after an RTT delay with the ID of the last stream the server will
+	// process.
+	//
+	// Therefore, when we get the first GoAway we don't necessarily close any
+	// streams. While in case of second GoAway we close all streams created after
+	// the GoAwayId. This way streams that were in-flight while the GoAway from
+	// server was being sent don't get killed.
+	select {
+	case <-t.goAway: // t.goAway has been closed (i.e.,multiple GoAways).
+		// If there are multiple GoAways the first one should always have an ID greater than the following ones.
+		if id > t.prevGoAwayID {
+			t.mu.Unlock()
+			t.Close()
+			return
+		}
+	default:
+		t.setGoAwayReason(f)
+		close(t.goAway)
+		t.state = draining
+		t.controlBuf.put(&incomingGoAway{})
+
+		// This has to be a new goroutine because we're still using the current goroutine to read in the transport.
+		t.onGoAway(t.goAwayReason)
+	}
+	// All streams with IDs greater than the GoAwayId
+	// and smaller than the previous GoAway ID should be killed.
+	upperLimit := t.prevGoAwayID
+	if upperLimit == 0 { // This is the first GoAway Frame.
+		upperLimit = math.MaxUint32 // Kill all streams after the GoAway ID.
+	}
+	for streamID, stream := range t.activeStreams {
+		if streamID > id && streamID <= upperLimit {
+			// The stream was unprocessed by the server.
+			atomic.StoreUint32(&stream.unprocessed, 1)
+			t.closeStream(stream, errStreamDrain, false, http2.ErrCodeNo, statusGoAway, nil, false)
+		}
+	}
+	t.prevGoAwayID = id
+	active := len(t.activeStreams)
+	t.mu.Unlock()
+	if active == 0 {
+		t.Close()
+	}
+}
+
+// setGoAwayReason sets the value of t.goAwayReason based
+// on the GoAway frame received.
+// It expects a lock on transport's mutext to be held by
+// the caller.
+func (t *http2Client) setGoAwayReason(f *http2.GoAwayFrame) {
+	t.goAwayReason = GoAwayNoReason
+	switch f.ErrCode {
+	case http2.ErrCodeEnhanceYourCalm:
+		if string(f.DebugData()) == "too_many_pings" {
+			t.goAwayReason = GoAwayTooManyPings
+		}
+	}
+}
+
+func (t *http2Client) GetGoAwayReason() GoAwayReason {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	return t.goAwayReason
+}
+
+func (t *http2Client) handleWindowUpdate(f *http2.WindowUpdateFrame) {
+	t.controlBuf.put(&incomingWindowUpdate{
+		streamID:  f.Header().StreamID,
+		increment: f.Increment,
+	})
+}
+
+// operateHeaders takes action on the decoded headers.
+func (t *http2Client) operateHeaders(frame *http2.MetaHeadersFrame) {
+	s, ok := t.getStream(frame)
+	if !ok {
+		return
+	}
+	atomic.StoreUint32(&s.bytesReceived, 1)
+	var state decodeState
+	if err := state.decodeHeader(frame); err != nil {
+		t.closeStream(s, err, true, http2.ErrCodeProtocol, status.New(codes.Internal, err.Error()), nil, false)
+		// Something wrong. Stops reading even when there is remaining.
+		return
+	}
+
+	endStream := frame.StreamEnded()
+	var isHeader bool
+	defer func() {
+		if t.statsHandler != nil {
+			if isHeader {
+				inHeader := &stats.InHeader{
+					Client:     true,
+					WireLength: int(frame.Header().Length),
+				}
+				t.statsHandler.HandleRPC(s.ctx, inHeader)
+			} else {
+				inTrailer := &stats.InTrailer{
+					Client:     true,
+					WireLength: int(frame.Header().Length),
+				}
+				t.statsHandler.HandleRPC(s.ctx, inTrailer)
+			}
+		}
+	}()
+	// If headers haven't been received yet.
+	if atomic.SwapUint32(&s.headerDone, 1) == 0 {
+		if !endStream {
+			// Headers frame is not actually a trailers-only frame.
+			isHeader = true
+			// These values can be set without any synchronization because
+			// stream goroutine will read it only after seeing a closed
+			// headerChan which we'll close after setting this.
+			s.recvCompress = state.encoding
+			if len(state.mdata) > 0 {
+				s.header = state.mdata
+			}
+		} else {
+			s.noHeaders = true
+		}
+		close(s.headerChan)
+	}
+	if !endStream {
+		return
+	}
+	// if client received END_STREAM from server while stream was still active, send RST_STREAM
+	rst := s.getState() == streamActive
+	t.closeStream(s, io.EOF, rst, http2.ErrCodeNo, state.status(), state.mdata, true)
+}
+
+// reader runs as a separate goroutine in charge of reading data from network
+// connection.
+//
+// TODO(zhaoq): currently one reader per transport. Investigate whether this is
+// optimal.
+// TODO(zhaoq): Check the validity of the incoming frame sequence.
+func (t *http2Client) reader() {
+	defer close(t.readerDone)
+	// Check the validity of server preface.
+	frame, err := t.framer.fr.ReadFrame()
+	if err != nil {
+		t.Close() // this kicks off resetTransport, so must be last before return
+		return
+	}
+	t.conn.SetReadDeadline(time.Time{}) // reset deadline once we get the settings frame (we didn't time out, yay!)
+	if t.keepaliveEnabled {
+		atomic.CompareAndSwapUint32(&t.activity, 0, 1)
+	}
+	sf, ok := frame.(*http2.SettingsFrame)
+	if !ok {
+		t.Close() // this kicks off resetTransport, so must be last before return
+		return
+	}
+	t.onSuccess()
+	t.handleSettings(sf, true)
+
+	// loop to keep reading incoming messages on this transport.
+	for {
+		frame, err := t.framer.fr.ReadFrame()
+		if t.keepaliveEnabled {
+			atomic.CompareAndSwapUint32(&t.activity, 0, 1)
+		}
+		if err != nil {
+			// Abort an active stream if the http2.Framer returns a
+			// http2.StreamError. This can happen only if the server's response
+			// is malformed http2.
+			if se, ok := err.(http2.StreamError); ok {
+				t.mu.Lock()
+				s := t.activeStreams[se.StreamID]
+				t.mu.Unlock()
+				if s != nil {
+					// use error detail to provide better err message
+					code := http2ErrConvTab[se.Code]
+					msg := t.framer.fr.ErrorDetail().Error()
+					t.closeStream(s, status.Error(code, msg), true, http2.ErrCodeProtocol, status.New(code, msg), nil, false)
+				}
+				continue
+			} else {
+				// Transport error.
+				t.Close()
+				return
+			}
+		}
+		switch frame := frame.(type) {
+		case *http2.MetaHeadersFrame:
+			t.operateHeaders(frame)
+		case *http2.DataFrame:
+			t.handleData(frame)
+		case *http2.RSTStreamFrame:
+			t.handleRSTStream(frame)
+		case *http2.SettingsFrame:
+			t.handleSettings(frame, false)
+		case *http2.PingFrame:
+			t.handlePing(frame)
+		case *http2.GoAwayFrame:
+			t.handleGoAway(frame)
+		case *http2.WindowUpdateFrame:
+			t.handleWindowUpdate(frame)
+		default:
+			errorf("transport: http2Client.reader got unhandled frame type %v.", frame)
+		}
+	}
+}
+
+// keepalive running in a separate goroutune makes sure the connection is alive by sending pings.
+func (t *http2Client) keepalive() {
+	p := &ping{data: [8]byte{}}
+	timer := time.NewTimer(t.kp.Time)
+	for {
+		select {
+		case <-timer.C:
+			if atomic.CompareAndSwapUint32(&t.activity, 1, 0) {
+				timer.Reset(t.kp.Time)
+				continue
+			}
+			// Check if keepalive should go dormant.
+			t.mu.Lock()
+			if len(t.activeStreams) < 1 && !t.kp.PermitWithoutStream {
+				// Make awakenKeepalive writable.
+				<-t.awakenKeepalive
+				t.mu.Unlock()
+				select {
+				case <-t.awakenKeepalive:
+					// If the control gets here a ping has been sent
+					// need to reset the timer with keepalive.Timeout.
+				case <-t.ctx.Done():
+					return
+				}
+			} else {
+				t.mu.Unlock()
+				if channelz.IsOn() {
+					atomic.AddInt64(&t.czData.kpCount, 1)
+				}
+				// Send ping.
+				t.controlBuf.put(p)
+			}
+
+			// By the time control gets here a ping has been sent one way or the other.
+			timer.Reset(t.kp.Timeout)
+			select {
+			case <-timer.C:
+				if atomic.CompareAndSwapUint32(&t.activity, 1, 0) {
+					timer.Reset(t.kp.Time)
+					continue
+				}
+				t.Close()
+				return
+			case <-t.ctx.Done():
+				if !timer.Stop() {
+					<-timer.C
+				}
+				return
+			}
+		case <-t.ctx.Done():
+			if !timer.Stop() {
+				<-timer.C
+			}
+			return
+		}
+	}
+}
+
+func (t *http2Client) Error() <-chan struct{} {
+	return t.ctx.Done()
+}
+
+func (t *http2Client) GoAway() <-chan struct{} {
+	return t.goAway
+}
+
+func (t *http2Client) ChannelzMetric() *channelz.SocketInternalMetric {
+	s := channelz.SocketInternalMetric{
+		StreamsStarted:                  atomic.LoadInt64(&t.czData.streamsStarted),
+		StreamsSucceeded:                atomic.LoadInt64(&t.czData.streamsSucceeded),
+		StreamsFailed:                   atomic.LoadInt64(&t.czData.streamsFailed),
+		MessagesSent:                    atomic.LoadInt64(&t.czData.msgSent),
+		MessagesReceived:                atomic.LoadInt64(&t.czData.msgRecv),
+		KeepAlivesSent:                  atomic.LoadInt64(&t.czData.kpCount),
+		LastLocalStreamCreatedTimestamp: time.Unix(0, atomic.LoadInt64(&t.czData.lastStreamCreatedTime)),
+		LastMessageSentTimestamp:        time.Unix(0, atomic.LoadInt64(&t.czData.lastMsgSentTime)),
+		LastMessageReceivedTimestamp:    time.Unix(0, atomic.LoadInt64(&t.czData.lastMsgRecvTime)),
+		LocalFlowControlWindow:          int64(t.fc.getSize()),
+		SocketOptions:                   channelz.GetSocketOption(t.conn),
+		LocalAddr:                       t.localAddr,
+		RemoteAddr:                      t.remoteAddr,
+		// RemoteName :
+	}
+	if au, ok := t.authInfo.(credentials.ChannelzSecurityInfo); ok {
+		s.Security = au.GetSecurityValue()
+	}
+	s.RemoteFlowControlWindow = t.getOutFlowWindow()
+	return &s
+}
+
+func (t *http2Client) IncrMsgSent() {
+	atomic.AddInt64(&t.czData.msgSent, 1)
+	atomic.StoreInt64(&t.czData.lastMsgSentTime, time.Now().UnixNano())
+}
+
+func (t *http2Client) IncrMsgRecv() {
+	atomic.AddInt64(&t.czData.msgRecv, 1)
+	atomic.StoreInt64(&t.czData.lastMsgRecvTime, time.Now().UnixNano())
+}
+
+func (t *http2Client) getOutFlowWindow() int64 {
+	resp := make(chan uint32, 1)
+	timer := time.NewTimer(time.Second)
+	defer timer.Stop()
+	t.controlBuf.put(&outFlowControlSizeRequest{resp})
+	select {
+	case sz := <-resp:
+		return int64(sz)
+	case <-t.ctxDone:
+		return -1
+	case <-timer.C:
+		return -2
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/http2_server.go b/go/vendor/google.golang.org/grpc/internal/transport/http2_server.go
new file mode 100644
index 0000000..efb7f53
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/http2_server.go
@@ -0,0 +1,1180 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"net"
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/golang/protobuf/proto"
+	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/internal/grpcrand"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/tap"
+)
+
+var (
+	// ErrIllegalHeaderWrite indicates that setting header is illegal because of
+	// the stream's state.
+	ErrIllegalHeaderWrite = errors.New("transport: the stream is done or WriteHeader was already called")
+	// ErrHeaderListSizeLimitViolation indicates that the header list size is larger
+	// than the limit set by peer.
+	ErrHeaderListSizeLimitViolation = errors.New("transport: trying to send header list size larger than the limit set by peer")
+)
+
+// http2Server implements the ServerTransport interface with HTTP2.
+type http2Server struct {
+	ctx         context.Context
+	ctxDone     <-chan struct{} // Cache the context.Done() chan
+	cancel      context.CancelFunc
+	conn        net.Conn
+	loopy       *loopyWriter
+	readerDone  chan struct{} // sync point to enable testing.
+	writerDone  chan struct{} // sync point to enable testing.
+	remoteAddr  net.Addr
+	localAddr   net.Addr
+	maxStreamID uint32               // max stream ID ever seen
+	authInfo    credentials.AuthInfo // auth info about the connection
+	inTapHandle tap.ServerInHandle
+	framer      *framer
+	// The max number of concurrent streams.
+	maxStreams uint32
+	// controlBuf delivers all the control related tasks (e.g., window
+	// updates, reset streams, and various settings) to the controller.
+	controlBuf *controlBuffer
+	fc         *trInFlow
+	stats      stats.Handler
+	// Flag to keep track of reading activity on transport.
+	// 1 is true and 0 is false.
+	activity uint32 // Accessed atomically.
+	// Keepalive and max-age parameters for the server.
+	kp keepalive.ServerParameters
+
+	// Keepalive enforcement policy.
+	kep keepalive.EnforcementPolicy
+	// The time instance last ping was received.
+	lastPingAt time.Time
+	// Number of times the client has violated keepalive ping policy so far.
+	pingStrikes uint8
+	// Flag to signify that number of ping strikes should be reset to 0.
+	// This is set whenever data or header frames are sent.
+	// 1 means yes.
+	resetPingStrikes      uint32 // Accessed atomically.
+	initialWindowSize     int32
+	bdpEst                *bdpEstimator
+	maxSendHeaderListSize *uint32
+
+	mu sync.Mutex // guard the following
+
+	// drainChan is initialized when drain(...) is called the first time.
+	// After which the server writes out the first GoAway(with ID 2^31-1) frame.
+	// Then an independent goroutine will be launched to later send the second GoAway.
+	// During this time we don't want to write another first GoAway(with ID 2^31 -1) frame.
+	// Thus call to drain(...) will be a no-op if drainChan is already initialized since draining is
+	// already underway.
+	drainChan     chan struct{}
+	state         transportState
+	activeStreams map[uint32]*Stream
+	// idle is the time instant when the connection went idle.
+	// This is either the beginning of the connection or when the number of
+	// RPCs go down to 0.
+	// When the connection is busy, this value is set to 0.
+	idle time.Time
+
+	// Fields below are for channelz metric collection.
+	channelzID int64 // channelz unique identification number
+	czData     *channelzData
+}
+
+// newHTTP2Server constructs a ServerTransport based on HTTP2. ConnectionError is
+// returned if something goes wrong.
+func newHTTP2Server(conn net.Conn, config *ServerConfig) (_ ServerTransport, err error) {
+	writeBufSize := config.WriteBufferSize
+	readBufSize := config.ReadBufferSize
+	maxHeaderListSize := defaultServerMaxHeaderListSize
+	if config.MaxHeaderListSize != nil {
+		maxHeaderListSize = *config.MaxHeaderListSize
+	}
+	framer := newFramer(conn, writeBufSize, readBufSize, maxHeaderListSize)
+	// Send initial settings as connection preface to client.
+	var isettings []http2.Setting
+	// TODO(zhaoq): Have a better way to signal "no limit" because 0 is
+	// permitted in the HTTP2 spec.
+	maxStreams := config.MaxStreams
+	if maxStreams == 0 {
+		maxStreams = math.MaxUint32
+	} else {
+		isettings = append(isettings, http2.Setting{
+			ID:  http2.SettingMaxConcurrentStreams,
+			Val: maxStreams,
+		})
+	}
+	dynamicWindow := true
+	iwz := int32(initialWindowSize)
+	if config.InitialWindowSize >= defaultWindowSize {
+		iwz = config.InitialWindowSize
+		dynamicWindow = false
+	}
+	icwz := int32(initialWindowSize)
+	if config.InitialConnWindowSize >= defaultWindowSize {
+		icwz = config.InitialConnWindowSize
+		dynamicWindow = false
+	}
+	if iwz != defaultWindowSize {
+		isettings = append(isettings, http2.Setting{
+			ID:  http2.SettingInitialWindowSize,
+			Val: uint32(iwz)})
+	}
+	if config.MaxHeaderListSize != nil {
+		isettings = append(isettings, http2.Setting{
+			ID:  http2.SettingMaxHeaderListSize,
+			Val: *config.MaxHeaderListSize,
+		})
+	}
+	if err := framer.fr.WriteSettings(isettings...); err != nil {
+		return nil, connectionErrorf(false, err, "transport: %v", err)
+	}
+	// Adjust the connection flow control window if needed.
+	if delta := uint32(icwz - defaultWindowSize); delta > 0 {
+		if err := framer.fr.WriteWindowUpdate(0, delta); err != nil {
+			return nil, connectionErrorf(false, err, "transport: %v", err)
+		}
+	}
+	kp := config.KeepaliveParams
+	if kp.MaxConnectionIdle == 0 {
+		kp.MaxConnectionIdle = defaultMaxConnectionIdle
+	}
+	if kp.MaxConnectionAge == 0 {
+		kp.MaxConnectionAge = defaultMaxConnectionAge
+	}
+	// Add a jitter to MaxConnectionAge.
+	kp.MaxConnectionAge += getJitter(kp.MaxConnectionAge)
+	if kp.MaxConnectionAgeGrace == 0 {
+		kp.MaxConnectionAgeGrace = defaultMaxConnectionAgeGrace
+	}
+	if kp.Time == 0 {
+		kp.Time = defaultServerKeepaliveTime
+	}
+	if kp.Timeout == 0 {
+		kp.Timeout = defaultServerKeepaliveTimeout
+	}
+	kep := config.KeepalivePolicy
+	if kep.MinTime == 0 {
+		kep.MinTime = defaultKeepalivePolicyMinTime
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	t := &http2Server{
+		ctx:               ctx,
+		cancel:            cancel,
+		ctxDone:           ctx.Done(),
+		conn:              conn,
+		remoteAddr:        conn.RemoteAddr(),
+		localAddr:         conn.LocalAddr(),
+		authInfo:          config.AuthInfo,
+		framer:            framer,
+		readerDone:        make(chan struct{}),
+		writerDone:        make(chan struct{}),
+		maxStreams:        maxStreams,
+		inTapHandle:       config.InTapHandle,
+		fc:                &trInFlow{limit: uint32(icwz)},
+		state:             reachable,
+		activeStreams:     make(map[uint32]*Stream),
+		stats:             config.StatsHandler,
+		kp:                kp,
+		idle:              time.Now(),
+		kep:               kep,
+		initialWindowSize: iwz,
+		czData:            new(channelzData),
+	}
+	t.controlBuf = newControlBuffer(t.ctxDone)
+	if dynamicWindow {
+		t.bdpEst = &bdpEstimator{
+			bdp:               initialWindowSize,
+			updateFlowControl: t.updateFlowControl,
+		}
+	}
+	if t.stats != nil {
+		t.ctx = t.stats.TagConn(t.ctx, &stats.ConnTagInfo{
+			RemoteAddr: t.remoteAddr,
+			LocalAddr:  t.localAddr,
+		})
+		connBegin := &stats.ConnBegin{}
+		t.stats.HandleConn(t.ctx, connBegin)
+	}
+	if channelz.IsOn() {
+		t.channelzID = channelz.RegisterNormalSocket(t, config.ChannelzParentID, "")
+	}
+	t.framer.writer.Flush()
+
+	defer func() {
+		if err != nil {
+			t.Close()
+		}
+	}()
+
+	// Check the validity of client preface.
+	preface := make([]byte, len(clientPreface))
+	if _, err := io.ReadFull(t.conn, preface); err != nil {
+		return nil, connectionErrorf(false, err, "transport: http2Server.HandleStreams failed to receive the preface from client: %v", err)
+	}
+	if !bytes.Equal(preface, clientPreface) {
+		return nil, connectionErrorf(false, nil, "transport: http2Server.HandleStreams received bogus greeting from client: %q", preface)
+	}
+
+	frame, err := t.framer.fr.ReadFrame()
+	if err == io.EOF || err == io.ErrUnexpectedEOF {
+		return nil, err
+	}
+	if err != nil {
+		return nil, connectionErrorf(false, err, "transport: http2Server.HandleStreams failed to read initial settings frame: %v", err)
+	}
+	atomic.StoreUint32(&t.activity, 1)
+	sf, ok := frame.(*http2.SettingsFrame)
+	if !ok {
+		return nil, connectionErrorf(false, nil, "transport: http2Server.HandleStreams saw invalid preface type %T from client", frame)
+	}
+	t.handleSettings(sf)
+
+	go func() {
+		t.loopy = newLoopyWriter(serverSide, t.framer, t.controlBuf, t.bdpEst)
+		t.loopy.ssGoAwayHandler = t.outgoingGoAwayHandler
+		if err := t.loopy.run(); err != nil {
+			errorf("transport: loopyWriter.run returning. Err: %v", err)
+		}
+		t.conn.Close()
+		close(t.writerDone)
+	}()
+	go t.keepalive()
+	return t, nil
+}
+
+// operateHeader takes action on the decoded headers.
+func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(*Stream), traceCtx func(context.Context, string) context.Context) (fatal bool) {
+	streamID := frame.Header().StreamID
+	state := decodeState{serverSide: true}
+	if err := state.decodeHeader(frame); err != nil {
+		if se, ok := status.FromError(err); ok {
+			t.controlBuf.put(&cleanupStream{
+				streamID: streamID,
+				rst:      true,
+				rstCode:  statusCodeConvTab[se.Code()],
+				onWrite:  func() {},
+			})
+		}
+		return false
+	}
+
+	buf := newRecvBuffer()
+	s := &Stream{
+		id:             streamID,
+		st:             t,
+		buf:            buf,
+		fc:             &inFlow{limit: uint32(t.initialWindowSize)},
+		recvCompress:   state.encoding,
+		method:         state.method,
+		contentSubtype: state.contentSubtype,
+	}
+	if frame.StreamEnded() {
+		// s is just created by the caller. No lock needed.
+		s.state = streamReadDone
+	}
+	if state.timeoutSet {
+		s.ctx, s.cancel = context.WithTimeout(t.ctx, state.timeout)
+	} else {
+		s.ctx, s.cancel = context.WithCancel(t.ctx)
+	}
+	pr := &peer.Peer{
+		Addr: t.remoteAddr,
+	}
+	// Attach Auth info if there is any.
+	if t.authInfo != nil {
+		pr.AuthInfo = t.authInfo
+	}
+	s.ctx = peer.NewContext(s.ctx, pr)
+	// Attach the received metadata to the context.
+	if len(state.mdata) > 0 {
+		s.ctx = metadata.NewIncomingContext(s.ctx, state.mdata)
+	}
+	if state.statsTags != nil {
+		s.ctx = stats.SetIncomingTags(s.ctx, state.statsTags)
+	}
+	if state.statsTrace != nil {
+		s.ctx = stats.SetIncomingTrace(s.ctx, state.statsTrace)
+	}
+	if t.inTapHandle != nil {
+		var err error
+		info := &tap.Info{
+			FullMethodName: state.method,
+		}
+		s.ctx, err = t.inTapHandle(s.ctx, info)
+		if err != nil {
+			warningf("transport: http2Server.operateHeaders got an error from InTapHandle: %v", err)
+			t.controlBuf.put(&cleanupStream{
+				streamID: s.id,
+				rst:      true,
+				rstCode:  http2.ErrCodeRefusedStream,
+				onWrite:  func() {},
+			})
+			return false
+		}
+	}
+	t.mu.Lock()
+	if t.state != reachable {
+		t.mu.Unlock()
+		return false
+	}
+	if uint32(len(t.activeStreams)) >= t.maxStreams {
+		t.mu.Unlock()
+		t.controlBuf.put(&cleanupStream{
+			streamID: streamID,
+			rst:      true,
+			rstCode:  http2.ErrCodeRefusedStream,
+			onWrite:  func() {},
+		})
+		return false
+	}
+	if streamID%2 != 1 || streamID <= t.maxStreamID {
+		t.mu.Unlock()
+		// illegal gRPC stream id.
+		errorf("transport: http2Server.HandleStreams received an illegal stream id: %v", streamID)
+		return true
+	}
+	t.maxStreamID = streamID
+	t.activeStreams[streamID] = s
+	if len(t.activeStreams) == 1 {
+		t.idle = time.Time{}
+	}
+	t.mu.Unlock()
+	if channelz.IsOn() {
+		atomic.AddInt64(&t.czData.streamsStarted, 1)
+		atomic.StoreInt64(&t.czData.lastStreamCreatedTime, time.Now().UnixNano())
+	}
+	s.requestRead = func(n int) {
+		t.adjustWindow(s, uint32(n))
+	}
+	s.ctx = traceCtx(s.ctx, s.method)
+	if t.stats != nil {
+		s.ctx = t.stats.TagRPC(s.ctx, &stats.RPCTagInfo{FullMethodName: s.method})
+		inHeader := &stats.InHeader{
+			FullMethod:  s.method,
+			RemoteAddr:  t.remoteAddr,
+			LocalAddr:   t.localAddr,
+			Compression: s.recvCompress,
+			WireLength:  int(frame.Header().Length),
+		}
+		t.stats.HandleRPC(s.ctx, inHeader)
+	}
+	s.ctxDone = s.ctx.Done()
+	s.wq = newWriteQuota(defaultWriteQuota, s.ctxDone)
+	s.trReader = &transportReader{
+		reader: &recvBufferReader{
+			ctx:     s.ctx,
+			ctxDone: s.ctxDone,
+			recv:    s.buf,
+		},
+		windowHandler: func(n int) {
+			t.updateWindow(s, uint32(n))
+		},
+	}
+	// Register the stream with loopy.
+	t.controlBuf.put(&registerStream{
+		streamID: s.id,
+		wq:       s.wq,
+	})
+	handle(s)
+	return false
+}
+
+// HandleStreams receives incoming streams using the given handler. This is
+// typically run in a separate goroutine.
+// traceCtx attaches trace to ctx and returns the new context.
+func (t *http2Server) HandleStreams(handle func(*Stream), traceCtx func(context.Context, string) context.Context) {
+	defer close(t.readerDone)
+	for {
+		frame, err := t.framer.fr.ReadFrame()
+		atomic.StoreUint32(&t.activity, 1)
+		if err != nil {
+			if se, ok := err.(http2.StreamError); ok {
+				warningf("transport: http2Server.HandleStreams encountered http2.StreamError: %v", se)
+				t.mu.Lock()
+				s := t.activeStreams[se.StreamID]
+				t.mu.Unlock()
+				if s != nil {
+					t.closeStream(s, true, se.Code, nil, false)
+				} else {
+					t.controlBuf.put(&cleanupStream{
+						streamID: se.StreamID,
+						rst:      true,
+						rstCode:  se.Code,
+						onWrite:  func() {},
+					})
+				}
+				continue
+			}
+			if err == io.EOF || err == io.ErrUnexpectedEOF {
+				t.Close()
+				return
+			}
+			warningf("transport: http2Server.HandleStreams failed to read frame: %v", err)
+			t.Close()
+			return
+		}
+		switch frame := frame.(type) {
+		case *http2.MetaHeadersFrame:
+			if t.operateHeaders(frame, handle, traceCtx) {
+				t.Close()
+				break
+			}
+		case *http2.DataFrame:
+			t.handleData(frame)
+		case *http2.RSTStreamFrame:
+			t.handleRSTStream(frame)
+		case *http2.SettingsFrame:
+			t.handleSettings(frame)
+		case *http2.PingFrame:
+			t.handlePing(frame)
+		case *http2.WindowUpdateFrame:
+			t.handleWindowUpdate(frame)
+		case *http2.GoAwayFrame:
+			// TODO: Handle GoAway from the client appropriately.
+		default:
+			errorf("transport: http2Server.HandleStreams found unhandled frame type %v.", frame)
+		}
+	}
+}
+
+func (t *http2Server) getStream(f http2.Frame) (*Stream, bool) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.activeStreams == nil {
+		// The transport is closing.
+		return nil, false
+	}
+	s, ok := t.activeStreams[f.Header().StreamID]
+	if !ok {
+		// The stream is already done.
+		return nil, false
+	}
+	return s, true
+}
+
+// adjustWindow sends out extra window update over the initial window size
+// of stream if the application is requesting data larger in size than
+// the window.
+func (t *http2Server) adjustWindow(s *Stream, n uint32) {
+	if w := s.fc.maybeAdjust(n); w > 0 {
+		t.controlBuf.put(&outgoingWindowUpdate{streamID: s.id, increment: w})
+	}
+
+}
+
+// updateWindow adjusts the inbound quota for the stream and the transport.
+// Window updates will deliver to the controller for sending when
+// the cumulative quota exceeds the corresponding threshold.
+func (t *http2Server) updateWindow(s *Stream, n uint32) {
+	if w := s.fc.onRead(n); w > 0 {
+		t.controlBuf.put(&outgoingWindowUpdate{streamID: s.id,
+			increment: w,
+		})
+	}
+}
+
+// updateFlowControl updates the incoming flow control windows
+// for the transport and the stream based on the current bdp
+// estimation.
+func (t *http2Server) updateFlowControl(n uint32) {
+	t.mu.Lock()
+	for _, s := range t.activeStreams {
+		s.fc.newLimit(n)
+	}
+	t.initialWindowSize = int32(n)
+	t.mu.Unlock()
+	t.controlBuf.put(&outgoingWindowUpdate{
+		streamID:  0,
+		increment: t.fc.newLimit(n),
+	})
+	t.controlBuf.put(&outgoingSettings{
+		ss: []http2.Setting{
+			{
+				ID:  http2.SettingInitialWindowSize,
+				Val: n,
+			},
+		},
+	})
+
+}
+
+func (t *http2Server) handleData(f *http2.DataFrame) {
+	size := f.Header().Length
+	var sendBDPPing bool
+	if t.bdpEst != nil {
+		sendBDPPing = t.bdpEst.add(size)
+	}
+	// Decouple connection's flow control from application's read.
+	// An update on connection's flow control should not depend on
+	// whether user application has read the data or not. Such a
+	// restriction is already imposed on the stream's flow control,
+	// and therefore the sender will be blocked anyways.
+	// Decoupling the connection flow control will prevent other
+	// active(fast) streams from starving in presence of slow or
+	// inactive streams.
+	if w := t.fc.onData(size); w > 0 {
+		t.controlBuf.put(&outgoingWindowUpdate{
+			streamID:  0,
+			increment: w,
+		})
+	}
+	if sendBDPPing {
+		// Avoid excessive ping detection (e.g. in an L7 proxy)
+		// by sending a window update prior to the BDP ping.
+		if w := t.fc.reset(); w > 0 {
+			t.controlBuf.put(&outgoingWindowUpdate{
+				streamID:  0,
+				increment: w,
+			})
+		}
+		t.controlBuf.put(bdpPing)
+	}
+	// Select the right stream to dispatch.
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	if size > 0 {
+		if err := s.fc.onData(size); err != nil {
+			t.closeStream(s, true, http2.ErrCodeFlowControl, nil, false)
+			return
+		}
+		if f.Header().Flags.Has(http2.FlagDataPadded) {
+			if w := s.fc.onRead(size - uint32(len(f.Data()))); w > 0 {
+				t.controlBuf.put(&outgoingWindowUpdate{s.id, w})
+			}
+		}
+		// TODO(bradfitz, zhaoq): A copy is required here because there is no
+		// guarantee f.Data() is consumed before the arrival of next frame.
+		// Can this copy be eliminated?
+		if len(f.Data()) > 0 {
+			data := make([]byte, len(f.Data()))
+			copy(data, f.Data())
+			s.write(recvMsg{data: data})
+		}
+	}
+	if f.Header().Flags.Has(http2.FlagDataEndStream) {
+		// Received the end of stream from the client.
+		s.compareAndSwapState(streamActive, streamReadDone)
+		s.write(recvMsg{err: io.EOF})
+	}
+}
+
+func (t *http2Server) handleRSTStream(f *http2.RSTStreamFrame) {
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	t.closeStream(s, false, 0, nil, false)
+}
+
+func (t *http2Server) handleSettings(f *http2.SettingsFrame) {
+	if f.IsAck() {
+		return
+	}
+	var ss []http2.Setting
+	var updateFuncs []func()
+	f.ForeachSetting(func(s http2.Setting) error {
+		switch s.ID {
+		case http2.SettingMaxHeaderListSize:
+			updateFuncs = append(updateFuncs, func() {
+				t.maxSendHeaderListSize = new(uint32)
+				*t.maxSendHeaderListSize = s.Val
+			})
+		default:
+			ss = append(ss, s)
+		}
+		return nil
+	})
+	t.controlBuf.executeAndPut(func(interface{}) bool {
+		for _, f := range updateFuncs {
+			f()
+		}
+		return true
+	}, &incomingSettings{
+		ss: ss,
+	})
+}
+
+const (
+	maxPingStrikes     = 2
+	defaultPingTimeout = 2 * time.Hour
+)
+
+func (t *http2Server) handlePing(f *http2.PingFrame) {
+	if f.IsAck() {
+		if f.Data == goAwayPing.data && t.drainChan != nil {
+			close(t.drainChan)
+			return
+		}
+		// Maybe it's a BDP ping.
+		if t.bdpEst != nil {
+			t.bdpEst.calculate(f.Data)
+		}
+		return
+	}
+	pingAck := &ping{ack: true}
+	copy(pingAck.data[:], f.Data[:])
+	t.controlBuf.put(pingAck)
+
+	now := time.Now()
+	defer func() {
+		t.lastPingAt = now
+	}()
+	// A reset ping strikes means that we don't need to check for policy
+	// violation for this ping and the pingStrikes counter should be set
+	// to 0.
+	if atomic.CompareAndSwapUint32(&t.resetPingStrikes, 1, 0) {
+		t.pingStrikes = 0
+		return
+	}
+	t.mu.Lock()
+	ns := len(t.activeStreams)
+	t.mu.Unlock()
+	if ns < 1 && !t.kep.PermitWithoutStream {
+		// Keepalive shouldn't be active thus, this new ping should
+		// have come after at least defaultPingTimeout.
+		if t.lastPingAt.Add(defaultPingTimeout).After(now) {
+			t.pingStrikes++
+		}
+	} else {
+		// Check if keepalive policy is respected.
+		if t.lastPingAt.Add(t.kep.MinTime).After(now) {
+			t.pingStrikes++
+		}
+	}
+
+	if t.pingStrikes > maxPingStrikes {
+		// Send goaway and close the connection.
+		errorf("transport: Got too many pings from the client, closing the connection.")
+		t.controlBuf.put(&goAway{code: http2.ErrCodeEnhanceYourCalm, debugData: []byte("too_many_pings"), closeConn: true})
+	}
+}
+
+func (t *http2Server) handleWindowUpdate(f *http2.WindowUpdateFrame) {
+	t.controlBuf.put(&incomingWindowUpdate{
+		streamID:  f.Header().StreamID,
+		increment: f.Increment,
+	})
+}
+
+func appendHeaderFieldsFromMD(headerFields []hpack.HeaderField, md metadata.MD) []hpack.HeaderField {
+	for k, vv := range md {
+		if isReservedHeader(k) {
+			// Clients don't tolerate reading restricted headers after some non restricted ones were sent.
+			continue
+		}
+		for _, v := range vv {
+			headerFields = append(headerFields, hpack.HeaderField{Name: k, Value: encodeMetadataHeader(k, v)})
+		}
+	}
+	return headerFields
+}
+
+func (t *http2Server) checkForHeaderListSize(it interface{}) bool {
+	if t.maxSendHeaderListSize == nil {
+		return true
+	}
+	hdrFrame := it.(*headerFrame)
+	var sz int64
+	for _, f := range hdrFrame.hf {
+		if sz += int64(f.Size()); sz > int64(*t.maxSendHeaderListSize) {
+			errorf("header list size to send violates the maximum size (%d bytes) set by client", *t.maxSendHeaderListSize)
+			return false
+		}
+	}
+	return true
+}
+
+// WriteHeader sends the header metedata md back to the client.
+func (t *http2Server) WriteHeader(s *Stream, md metadata.MD) error {
+	if s.updateHeaderSent() || s.getState() == streamDone {
+		return ErrIllegalHeaderWrite
+	}
+	s.hdrMu.Lock()
+	if md.Len() > 0 {
+		if s.header.Len() > 0 {
+			s.header = metadata.Join(s.header, md)
+		} else {
+			s.header = md
+		}
+	}
+	if err := t.writeHeaderLocked(s); err != nil {
+		s.hdrMu.Unlock()
+		return err
+	}
+	s.hdrMu.Unlock()
+	return nil
+}
+
+func (t *http2Server) writeHeaderLocked(s *Stream) error {
+	// TODO(mmukhi): Benchmark if the performance gets better if count the metadata and other header fields
+	// first and create a slice of that exact size.
+	headerFields := make([]hpack.HeaderField, 0, 2) // at least :status, content-type will be there if none else.
+	headerFields = append(headerFields, hpack.HeaderField{Name: ":status", Value: "200"})
+	headerFields = append(headerFields, hpack.HeaderField{Name: "content-type", Value: contentType(s.contentSubtype)})
+	if s.sendCompress != "" {
+		headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-encoding", Value: s.sendCompress})
+	}
+	headerFields = appendHeaderFieldsFromMD(headerFields, s.header)
+	success, err := t.controlBuf.executeAndPut(t.checkForHeaderListSize, &headerFrame{
+		streamID:  s.id,
+		hf:        headerFields,
+		endStream: false,
+		onWrite: func() {
+			atomic.StoreUint32(&t.resetPingStrikes, 1)
+		},
+	})
+	if !success {
+		if err != nil {
+			return err
+		}
+		t.closeStream(s, true, http2.ErrCodeInternal, nil, false)
+		return ErrHeaderListSizeLimitViolation
+	}
+	if t.stats != nil {
+		// Note: WireLength is not set in outHeader.
+		// TODO(mmukhi): Revisit this later, if needed.
+		outHeader := &stats.OutHeader{}
+		t.stats.HandleRPC(s.Context(), outHeader)
+	}
+	return nil
+}
+
+// WriteStatus sends stream status to the client and terminates the stream.
+// There is no further I/O operations being able to perform on this stream.
+// TODO(zhaoq): Now it indicates the end of entire stream. Revisit if early
+// OK is adopted.
+func (t *http2Server) WriteStatus(s *Stream, st *status.Status) error {
+	if s.getState() == streamDone {
+		return nil
+	}
+	s.hdrMu.Lock()
+	// TODO(mmukhi): Benchmark if the performance gets better if count the metadata and other header fields
+	// first and create a slice of that exact size.
+	headerFields := make([]hpack.HeaderField, 0, 2) // grpc-status and grpc-message will be there if none else.
+	if !s.updateHeaderSent() {                      // No headers have been sent.
+		if len(s.header) > 0 { // Send a separate header frame.
+			if err := t.writeHeaderLocked(s); err != nil {
+				s.hdrMu.Unlock()
+				return err
+			}
+		} else { // Send a trailer only response.
+			headerFields = append(headerFields, hpack.HeaderField{Name: ":status", Value: "200"})
+			headerFields = append(headerFields, hpack.HeaderField{Name: "content-type", Value: contentType(s.contentSubtype)})
+		}
+	}
+	headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-status", Value: strconv.Itoa(int(st.Code()))})
+	headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-message", Value: encodeGrpcMessage(st.Message())})
+
+	if p := st.Proto(); p != nil && len(p.Details) > 0 {
+		stBytes, err := proto.Marshal(p)
+		if err != nil {
+			// TODO: return error instead, when callers are able to handle it.
+			grpclog.Errorf("transport: failed to marshal rpc status: %v, error: %v", p, err)
+		} else {
+			headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-status-details-bin", Value: encodeBinHeader(stBytes)})
+		}
+	}
+
+	// Attach the trailer metadata.
+	headerFields = appendHeaderFieldsFromMD(headerFields, s.trailer)
+	trailingHeader := &headerFrame{
+		streamID:  s.id,
+		hf:        headerFields,
+		endStream: true,
+		onWrite: func() {
+			atomic.StoreUint32(&t.resetPingStrikes, 1)
+		},
+	}
+	s.hdrMu.Unlock()
+	success, err := t.controlBuf.execute(t.checkForHeaderListSize, trailingHeader)
+	if !success {
+		if err != nil {
+			return err
+		}
+		t.closeStream(s, true, http2.ErrCodeInternal, nil, false)
+		return ErrHeaderListSizeLimitViolation
+	}
+	t.closeStream(s, false, 0, trailingHeader, true)
+	if t.stats != nil {
+		t.stats.HandleRPC(s.Context(), &stats.OutTrailer{})
+	}
+	return nil
+}
+
+// Write converts the data into HTTP2 data frame and sends it out. Non-nil error
+// is returns if it fails (e.g., framing error, transport error).
+func (t *http2Server) Write(s *Stream, hdr []byte, data []byte, opts *Options) error {
+	if !s.isHeaderSent() { // Headers haven't been written yet.
+		if err := t.WriteHeader(s, nil); err != nil {
+			// TODO(mmukhi, dfawley): Make sure this is the right code to return.
+			return status.Errorf(codes.Internal, "transport: %v", err)
+		}
+	} else {
+		// Writing headers checks for this condition.
+		if s.getState() == streamDone {
+			// TODO(mmukhi, dfawley): Should the server write also return io.EOF?
+			s.cancel()
+			select {
+			case <-t.ctx.Done():
+				return ErrConnClosing
+			default:
+			}
+			return ContextErr(s.ctx.Err())
+		}
+	}
+	// Add some data to header frame so that we can equally distribute bytes across frames.
+	emptyLen := http2MaxFrameLen - len(hdr)
+	if emptyLen > len(data) {
+		emptyLen = len(data)
+	}
+	hdr = append(hdr, data[:emptyLen]...)
+	data = data[emptyLen:]
+	df := &dataFrame{
+		streamID: s.id,
+		h:        hdr,
+		d:        data,
+		onEachWrite: func() {
+			atomic.StoreUint32(&t.resetPingStrikes, 1)
+		},
+	}
+	if err := s.wq.get(int32(len(hdr) + len(data))); err != nil {
+		select {
+		case <-t.ctx.Done():
+			return ErrConnClosing
+		default:
+		}
+		return ContextErr(s.ctx.Err())
+	}
+	return t.controlBuf.put(df)
+}
+
+// keepalive running in a separate goroutine does the following:
+// 1. Gracefully closes an idle connection after a duration of keepalive.MaxConnectionIdle.
+// 2. Gracefully closes any connection after a duration of keepalive.MaxConnectionAge.
+// 3. Forcibly closes a connection after an additive period of keepalive.MaxConnectionAgeGrace over keepalive.MaxConnectionAge.
+// 4. Makes sure a connection is alive by sending pings with a frequency of keepalive.Time and closes a non-responsive connection
+// after an additional duration of keepalive.Timeout.
+func (t *http2Server) keepalive() {
+	p := &ping{}
+	var pingSent bool
+	maxIdle := time.NewTimer(t.kp.MaxConnectionIdle)
+	maxAge := time.NewTimer(t.kp.MaxConnectionAge)
+	keepalive := time.NewTimer(t.kp.Time)
+	// NOTE: All exit paths of this function should reset their
+	// respective timers. A failure to do so will cause the
+	// following clean-up to deadlock and eventually leak.
+	defer func() {
+		if !maxIdle.Stop() {
+			<-maxIdle.C
+		}
+		if !maxAge.Stop() {
+			<-maxAge.C
+		}
+		if !keepalive.Stop() {
+			<-keepalive.C
+		}
+	}()
+	for {
+		select {
+		case <-maxIdle.C:
+			t.mu.Lock()
+			idle := t.idle
+			if idle.IsZero() { // The connection is non-idle.
+				t.mu.Unlock()
+				maxIdle.Reset(t.kp.MaxConnectionIdle)
+				continue
+			}
+			val := t.kp.MaxConnectionIdle - time.Since(idle)
+			t.mu.Unlock()
+			if val <= 0 {
+				// The connection has been idle for a duration of keepalive.MaxConnectionIdle or more.
+				// Gracefully close the connection.
+				t.drain(http2.ErrCodeNo, []byte{})
+				// Resetting the timer so that the clean-up doesn't deadlock.
+				maxIdle.Reset(infinity)
+				return
+			}
+			maxIdle.Reset(val)
+		case <-maxAge.C:
+			t.drain(http2.ErrCodeNo, []byte{})
+			maxAge.Reset(t.kp.MaxConnectionAgeGrace)
+			select {
+			case <-maxAge.C:
+				// Close the connection after grace period.
+				t.Close()
+				// Resetting the timer so that the clean-up doesn't deadlock.
+				maxAge.Reset(infinity)
+			case <-t.ctx.Done():
+			}
+			return
+		case <-keepalive.C:
+			if atomic.CompareAndSwapUint32(&t.activity, 1, 0) {
+				pingSent = false
+				keepalive.Reset(t.kp.Time)
+				continue
+			}
+			if pingSent {
+				t.Close()
+				// Resetting the timer so that the clean-up doesn't deadlock.
+				keepalive.Reset(infinity)
+				return
+			}
+			pingSent = true
+			if channelz.IsOn() {
+				atomic.AddInt64(&t.czData.kpCount, 1)
+			}
+			t.controlBuf.put(p)
+			keepalive.Reset(t.kp.Timeout)
+		case <-t.ctx.Done():
+			return
+		}
+	}
+}
+
+// Close starts shutting down the http2Server transport.
+// TODO(zhaoq): Now the destruction is not blocked on any pending streams. This
+// could cause some resource issue. Revisit this later.
+func (t *http2Server) Close() error {
+	t.mu.Lock()
+	if t.state == closing {
+		t.mu.Unlock()
+		return errors.New("transport: Close() was already called")
+	}
+	t.state = closing
+	streams := t.activeStreams
+	t.activeStreams = nil
+	t.mu.Unlock()
+	t.controlBuf.finish()
+	t.cancel()
+	err := t.conn.Close()
+	if channelz.IsOn() {
+		channelz.RemoveEntry(t.channelzID)
+	}
+	// Cancel all active streams.
+	for _, s := range streams {
+		s.cancel()
+	}
+	if t.stats != nil {
+		connEnd := &stats.ConnEnd{}
+		t.stats.HandleConn(t.ctx, connEnd)
+	}
+	return err
+}
+
+// closeStream clears the footprint of a stream when the stream is not needed
+// any more.
+func (t *http2Server) closeStream(s *Stream, rst bool, rstCode http2.ErrCode, hdr *headerFrame, eosReceived bool) {
+	if s.swapState(streamDone) == streamDone {
+		// If the stream was already done, return.
+		return
+	}
+	// In case stream sending and receiving are invoked in separate
+	// goroutines (e.g., bi-directional streaming), cancel needs to be
+	// called to interrupt the potential blocking on other goroutines.
+	s.cancel()
+	cleanup := &cleanupStream{
+		streamID: s.id,
+		rst:      rst,
+		rstCode:  rstCode,
+		onWrite: func() {
+			t.mu.Lock()
+			if t.activeStreams != nil {
+				delete(t.activeStreams, s.id)
+				if len(t.activeStreams) == 0 {
+					t.idle = time.Now()
+				}
+			}
+			t.mu.Unlock()
+			if channelz.IsOn() {
+				if eosReceived {
+					atomic.AddInt64(&t.czData.streamsSucceeded, 1)
+				} else {
+					atomic.AddInt64(&t.czData.streamsFailed, 1)
+				}
+			}
+		},
+	}
+	if hdr != nil {
+		hdr.cleanup = cleanup
+		t.controlBuf.put(hdr)
+	} else {
+		t.controlBuf.put(cleanup)
+	}
+}
+
+func (t *http2Server) RemoteAddr() net.Addr {
+	return t.remoteAddr
+}
+
+func (t *http2Server) Drain() {
+	t.drain(http2.ErrCodeNo, []byte{})
+}
+
+func (t *http2Server) drain(code http2.ErrCode, debugData []byte) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.drainChan != nil {
+		return
+	}
+	t.drainChan = make(chan struct{})
+	t.controlBuf.put(&goAway{code: code, debugData: debugData, headsUp: true})
+}
+
+var goAwayPing = &ping{data: [8]byte{1, 6, 1, 8, 0, 3, 3, 9}}
+
+// Handles outgoing GoAway and returns true if loopy needs to put itself
+// in draining mode.
+func (t *http2Server) outgoingGoAwayHandler(g *goAway) (bool, error) {
+	t.mu.Lock()
+	if t.state == closing { // TODO(mmukhi): This seems unnecessary.
+		t.mu.Unlock()
+		// The transport is closing.
+		return false, ErrConnClosing
+	}
+	sid := t.maxStreamID
+	if !g.headsUp {
+		// Stop accepting more streams now.
+		t.state = draining
+		if len(t.activeStreams) == 0 {
+			g.closeConn = true
+		}
+		t.mu.Unlock()
+		if err := t.framer.fr.WriteGoAway(sid, g.code, g.debugData); err != nil {
+			return false, err
+		}
+		if g.closeConn {
+			// Abruptly close the connection following the GoAway (via
+			// loopywriter).  But flush out what's inside the buffer first.
+			t.framer.writer.Flush()
+			return false, fmt.Errorf("transport: Connection closing")
+		}
+		return true, nil
+	}
+	t.mu.Unlock()
+	// For a graceful close, send out a GoAway with stream ID of MaxUInt32,
+	// Follow that with a ping and wait for the ack to come back or a timer
+	// to expire. During this time accept new streams since they might have
+	// originated before the GoAway reaches the client.
+	// After getting the ack or timer expiration send out another GoAway this
+	// time with an ID of the max stream server intends to process.
+	if err := t.framer.fr.WriteGoAway(math.MaxUint32, http2.ErrCodeNo, []byte{}); err != nil {
+		return false, err
+	}
+	if err := t.framer.fr.WritePing(false, goAwayPing.data); err != nil {
+		return false, err
+	}
+	go func() {
+		timer := time.NewTimer(time.Minute)
+		defer timer.Stop()
+		select {
+		case <-t.drainChan:
+		case <-timer.C:
+		case <-t.ctx.Done():
+			return
+		}
+		t.controlBuf.put(&goAway{code: g.code, debugData: g.debugData})
+	}()
+	return false, nil
+}
+
+func (t *http2Server) ChannelzMetric() *channelz.SocketInternalMetric {
+	s := channelz.SocketInternalMetric{
+		StreamsStarted:                   atomic.LoadInt64(&t.czData.streamsStarted),
+		StreamsSucceeded:                 atomic.LoadInt64(&t.czData.streamsSucceeded),
+		StreamsFailed:                    atomic.LoadInt64(&t.czData.streamsFailed),
+		MessagesSent:                     atomic.LoadInt64(&t.czData.msgSent),
+		MessagesReceived:                 atomic.LoadInt64(&t.czData.msgRecv),
+		KeepAlivesSent:                   atomic.LoadInt64(&t.czData.kpCount),
+		LastRemoteStreamCreatedTimestamp: time.Unix(0, atomic.LoadInt64(&t.czData.lastStreamCreatedTime)),
+		LastMessageSentTimestamp:         time.Unix(0, atomic.LoadInt64(&t.czData.lastMsgSentTime)),
+		LastMessageReceivedTimestamp:     time.Unix(0, atomic.LoadInt64(&t.czData.lastMsgRecvTime)),
+		LocalFlowControlWindow:           int64(t.fc.getSize()),
+		SocketOptions:                    channelz.GetSocketOption(t.conn),
+		LocalAddr:                        t.localAddr,
+		RemoteAddr:                       t.remoteAddr,
+		// RemoteName :
+	}
+	if au, ok := t.authInfo.(credentials.ChannelzSecurityInfo); ok {
+		s.Security = au.GetSecurityValue()
+	}
+	s.RemoteFlowControlWindow = t.getOutFlowWindow()
+	return &s
+}
+
+func (t *http2Server) IncrMsgSent() {
+	atomic.AddInt64(&t.czData.msgSent, 1)
+	atomic.StoreInt64(&t.czData.lastMsgSentTime, time.Now().UnixNano())
+}
+
+func (t *http2Server) IncrMsgRecv() {
+	atomic.AddInt64(&t.czData.msgRecv, 1)
+	atomic.StoreInt64(&t.czData.lastMsgRecvTime, time.Now().UnixNano())
+}
+
+func (t *http2Server) getOutFlowWindow() int64 {
+	resp := make(chan uint32)
+	timer := time.NewTimer(time.Second)
+	defer timer.Stop()
+	t.controlBuf.put(&outFlowControlSizeRequest{resp})
+	select {
+	case sz := <-resp:
+		return int64(sz)
+	case <-t.ctxDone:
+		return -1
+	case <-timer.C:
+		return -2
+	}
+}
+
+func getJitter(v time.Duration) time.Duration {
+	if v == infinity {
+		return 0
+	}
+	// Generate a jitter between +/- 10% of the value.
+	r := int64(v / 10)
+	j := grpcrand.Int63n(2*r) - r
+	return time.Duration(j)
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/http_util.go b/go/vendor/google.golang.org/grpc/internal/transport/http_util.go
new file mode 100644
index 0000000..77a2cfa
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/http_util.go
@@ -0,0 +1,623 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package transport
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"math"
+	"net"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/golang/protobuf/proto"
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+	spb "google.golang.org/genproto/googleapis/rpc/status"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+const (
+	// http2MaxFrameLen specifies the max length of a HTTP2 frame.
+	http2MaxFrameLen = 16384 // 16KB frame
+	// http://http2.github.io/http2-spec/#SettingValues
+	http2InitHeaderTableSize = 4096
+	// baseContentType is the base content-type for gRPC.  This is a valid
+	// content-type on it's own, but can also include a content-subtype such as
+	// "proto" as a suffix after "+" or ";".  See
+	// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests
+	// for more details.
+	baseContentType = "application/grpc"
+)
+
+var (
+	clientPreface   = []byte(http2.ClientPreface)
+	http2ErrConvTab = map[http2.ErrCode]codes.Code{
+		http2.ErrCodeNo:                 codes.Internal,
+		http2.ErrCodeProtocol:           codes.Internal,
+		http2.ErrCodeInternal:           codes.Internal,
+		http2.ErrCodeFlowControl:        codes.ResourceExhausted,
+		http2.ErrCodeSettingsTimeout:    codes.Internal,
+		http2.ErrCodeStreamClosed:       codes.Internal,
+		http2.ErrCodeFrameSize:          codes.Internal,
+		http2.ErrCodeRefusedStream:      codes.Unavailable,
+		http2.ErrCodeCancel:             codes.Canceled,
+		http2.ErrCodeCompression:        codes.Internal,
+		http2.ErrCodeConnect:            codes.Internal,
+		http2.ErrCodeEnhanceYourCalm:    codes.ResourceExhausted,
+		http2.ErrCodeInadequateSecurity: codes.PermissionDenied,
+		http2.ErrCodeHTTP11Required:     codes.Internal,
+	}
+	statusCodeConvTab = map[codes.Code]http2.ErrCode{
+		codes.Internal:          http2.ErrCodeInternal,
+		codes.Canceled:          http2.ErrCodeCancel,
+		codes.Unavailable:       http2.ErrCodeRefusedStream,
+		codes.ResourceExhausted: http2.ErrCodeEnhanceYourCalm,
+		codes.PermissionDenied:  http2.ErrCodeInadequateSecurity,
+	}
+	httpStatusConvTab = map[int]codes.Code{
+		// 400 Bad Request - INTERNAL.
+		http.StatusBadRequest: codes.Internal,
+		// 401 Unauthorized  - UNAUTHENTICATED.
+		http.StatusUnauthorized: codes.Unauthenticated,
+		// 403 Forbidden - PERMISSION_DENIED.
+		http.StatusForbidden: codes.PermissionDenied,
+		// 404 Not Found - UNIMPLEMENTED.
+		http.StatusNotFound: codes.Unimplemented,
+		// 429 Too Many Requests - UNAVAILABLE.
+		http.StatusTooManyRequests: codes.Unavailable,
+		// 502 Bad Gateway - UNAVAILABLE.
+		http.StatusBadGateway: codes.Unavailable,
+		// 503 Service Unavailable - UNAVAILABLE.
+		http.StatusServiceUnavailable: codes.Unavailable,
+		// 504 Gateway timeout - UNAVAILABLE.
+		http.StatusGatewayTimeout: codes.Unavailable,
+	}
+)
+
+// Records the states during HPACK decoding. Must be reset once the
+// decoding of the entire headers are finished.
+type decodeState struct {
+	encoding string
+	// statusGen caches the stream status received from the trailer the server
+	// sent.  Client side only.  Do not access directly.  After all trailers are
+	// parsed, use the status method to retrieve the status.
+	statusGen *status.Status
+	// rawStatusCode and rawStatusMsg are set from the raw trailer fields and are not
+	// intended for direct access outside of parsing.
+	rawStatusCode *int
+	rawStatusMsg  string
+	httpStatus    *int
+	// Server side only fields.
+	timeoutSet bool
+	timeout    time.Duration
+	method     string
+	// key-value metadata map from the peer.
+	mdata          map[string][]string
+	statsTags      []byte
+	statsTrace     []byte
+	contentSubtype string
+	// whether decoding on server side or not
+	serverSide bool
+}
+
+// isReservedHeader checks whether hdr belongs to HTTP2 headers
+// reserved by gRPC protocol. Any other headers are classified as the
+// user-specified metadata.
+func isReservedHeader(hdr string) bool {
+	if hdr != "" && hdr[0] == ':' {
+		return true
+	}
+	switch hdr {
+	case "content-type",
+		"user-agent",
+		"grpc-message-type",
+		"grpc-encoding",
+		"grpc-message",
+		"grpc-status",
+		"grpc-timeout",
+		"grpc-status-details-bin",
+		// Intentionally exclude grpc-previous-rpc-attempts and
+		// grpc-retry-pushback-ms, which are "reserved", but their API
+		// intentionally works via metadata.
+		"te":
+		return true
+	default:
+		return false
+	}
+}
+
+// isWhitelistedHeader checks whether hdr should be propagated into metadata
+// visible to users, even though it is classified as "reserved", above.
+func isWhitelistedHeader(hdr string) bool {
+	switch hdr {
+	case ":authority", "user-agent":
+		return true
+	default:
+		return false
+	}
+}
+
+// contentSubtype returns the content-subtype for the given content-type.  The
+// given content-type must be a valid content-type that starts with
+// "application/grpc". A content-subtype will follow "application/grpc" after a
+// "+" or ";". See
+// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
+// more details.
+//
+// If contentType is not a valid content-type for gRPC, the boolean
+// will be false, otherwise true. If content-type == "application/grpc",
+// "application/grpc+", or "application/grpc;", the boolean will be true,
+// but no content-subtype will be returned.
+//
+// contentType is assumed to be lowercase already.
+func contentSubtype(contentType string) (string, bool) {
+	if contentType == baseContentType {
+		return "", true
+	}
+	if !strings.HasPrefix(contentType, baseContentType) {
+		return "", false
+	}
+	// guaranteed since != baseContentType and has baseContentType prefix
+	switch contentType[len(baseContentType)] {
+	case '+', ';':
+		// this will return true for "application/grpc+" or "application/grpc;"
+		// which the previous validContentType function tested to be valid, so we
+		// just say that no content-subtype is specified in this case
+		return contentType[len(baseContentType)+1:], true
+	default:
+		return "", false
+	}
+}
+
+// contentSubtype is assumed to be lowercase
+func contentType(contentSubtype string) string {
+	if contentSubtype == "" {
+		return baseContentType
+	}
+	return baseContentType + "+" + contentSubtype
+}
+
+func (d *decodeState) status() *status.Status {
+	if d.statusGen == nil {
+		// No status-details were provided; generate status using code/msg.
+		d.statusGen = status.New(codes.Code(int32(*(d.rawStatusCode))), d.rawStatusMsg)
+	}
+	return d.statusGen
+}
+
+const binHdrSuffix = "-bin"
+
+func encodeBinHeader(v []byte) string {
+	return base64.RawStdEncoding.EncodeToString(v)
+}
+
+func decodeBinHeader(v string) ([]byte, error) {
+	if len(v)%4 == 0 {
+		// Input was padded, or padding was not necessary.
+		return base64.StdEncoding.DecodeString(v)
+	}
+	return base64.RawStdEncoding.DecodeString(v)
+}
+
+func encodeMetadataHeader(k, v string) string {
+	if strings.HasSuffix(k, binHdrSuffix) {
+		return encodeBinHeader(([]byte)(v))
+	}
+	return v
+}
+
+func decodeMetadataHeader(k, v string) (string, error) {
+	if strings.HasSuffix(k, binHdrSuffix) {
+		b, err := decodeBinHeader(v)
+		return string(b), err
+	}
+	return v, nil
+}
+
+func (d *decodeState) decodeHeader(frame *http2.MetaHeadersFrame) error {
+	// frame.Truncated is set to true when framer detects that the current header
+	// list size hits MaxHeaderListSize limit.
+	if frame.Truncated {
+		return status.Error(codes.Internal, "peer header list size exceeded limit")
+	}
+	for _, hf := range frame.Fields {
+		if err := d.processHeaderField(hf); err != nil {
+			return err
+		}
+	}
+
+	if d.serverSide {
+		return nil
+	}
+
+	// If grpc status exists, no need to check further.
+	if d.rawStatusCode != nil || d.statusGen != nil {
+		return nil
+	}
+
+	// If grpc status doesn't exist and http status doesn't exist,
+	// then it's a malformed header.
+	if d.httpStatus == nil {
+		return status.Error(codes.Internal, "malformed header: doesn't contain status(gRPC or HTTP)")
+	}
+
+	if *(d.httpStatus) != http.StatusOK {
+		code, ok := httpStatusConvTab[*(d.httpStatus)]
+		if !ok {
+			code = codes.Unknown
+		}
+		return status.Error(code, http.StatusText(*(d.httpStatus)))
+	}
+
+	// gRPC status doesn't exist and http status is OK.
+	// Set rawStatusCode to be unknown and return nil error.
+	// So that, if the stream has ended this Unknown status
+	// will be propagated to the user.
+	// Otherwise, it will be ignored. In which case, status from
+	// a later trailer, that has StreamEnded flag set, is propagated.
+	code := int(codes.Unknown)
+	d.rawStatusCode = &code
+	return nil
+}
+
+func (d *decodeState) addMetadata(k, v string) {
+	if d.mdata == nil {
+		d.mdata = make(map[string][]string)
+	}
+	d.mdata[k] = append(d.mdata[k], v)
+}
+
+func (d *decodeState) processHeaderField(f hpack.HeaderField) error {
+	switch f.Name {
+	case "content-type":
+		contentSubtype, validContentType := contentSubtype(f.Value)
+		if !validContentType {
+			return status.Errorf(codes.Internal, "transport: received the unexpected content-type %q", f.Value)
+		}
+		d.contentSubtype = contentSubtype
+		// TODO: do we want to propagate the whole content-type in the metadata,
+		// or come up with a way to just propagate the content-subtype if it was set?
+		// ie {"content-type": "application/grpc+proto"} or {"content-subtype": "proto"}
+		// in the metadata?
+		d.addMetadata(f.Name, f.Value)
+	case "grpc-encoding":
+		d.encoding = f.Value
+	case "grpc-status":
+		code, err := strconv.Atoi(f.Value)
+		if err != nil {
+			return status.Errorf(codes.Internal, "transport: malformed grpc-status: %v", err)
+		}
+		d.rawStatusCode = &code
+	case "grpc-message":
+		d.rawStatusMsg = decodeGrpcMessage(f.Value)
+	case "grpc-status-details-bin":
+		v, err := decodeBinHeader(f.Value)
+		if err != nil {
+			return status.Errorf(codes.Internal, "transport: malformed grpc-status-details-bin: %v", err)
+		}
+		s := &spb.Status{}
+		if err := proto.Unmarshal(v, s); err != nil {
+			return status.Errorf(codes.Internal, "transport: malformed grpc-status-details-bin: %v", err)
+		}
+		d.statusGen = status.FromProto(s)
+	case "grpc-timeout":
+		d.timeoutSet = true
+		var err error
+		if d.timeout, err = decodeTimeout(f.Value); err != nil {
+			return status.Errorf(codes.Internal, "transport: malformed time-out: %v", err)
+		}
+	case ":path":
+		d.method = f.Value
+	case ":status":
+		code, err := strconv.Atoi(f.Value)
+		if err != nil {
+			return status.Errorf(codes.Internal, "transport: malformed http-status: %v", err)
+		}
+		d.httpStatus = &code
+	case "grpc-tags-bin":
+		v, err := decodeBinHeader(f.Value)
+		if err != nil {
+			return status.Errorf(codes.Internal, "transport: malformed grpc-tags-bin: %v", err)
+		}
+		d.statsTags = v
+		d.addMetadata(f.Name, string(v))
+	case "grpc-trace-bin":
+		v, err := decodeBinHeader(f.Value)
+		if err != nil {
+			return status.Errorf(codes.Internal, "transport: malformed grpc-trace-bin: %v", err)
+		}
+		d.statsTrace = v
+		d.addMetadata(f.Name, string(v))
+	default:
+		if isReservedHeader(f.Name) && !isWhitelistedHeader(f.Name) {
+			break
+		}
+		v, err := decodeMetadataHeader(f.Name, f.Value)
+		if err != nil {
+			errorf("Failed to decode metadata header (%q, %q): %v", f.Name, f.Value, err)
+			return nil
+		}
+		d.addMetadata(f.Name, v)
+	}
+	return nil
+}
+
+type timeoutUnit uint8
+
+const (
+	hour        timeoutUnit = 'H'
+	minute      timeoutUnit = 'M'
+	second      timeoutUnit = 'S'
+	millisecond timeoutUnit = 'm'
+	microsecond timeoutUnit = 'u'
+	nanosecond  timeoutUnit = 'n'
+)
+
+func timeoutUnitToDuration(u timeoutUnit) (d time.Duration, ok bool) {
+	switch u {
+	case hour:
+		return time.Hour, true
+	case minute:
+		return time.Minute, true
+	case second:
+		return time.Second, true
+	case millisecond:
+		return time.Millisecond, true
+	case microsecond:
+		return time.Microsecond, true
+	case nanosecond:
+		return time.Nanosecond, true
+	default:
+	}
+	return
+}
+
+const maxTimeoutValue int64 = 100000000 - 1
+
+// div does integer division and round-up the result. Note that this is
+// equivalent to (d+r-1)/r but has less chance to overflow.
+func div(d, r time.Duration) int64 {
+	if m := d % r; m > 0 {
+		return int64(d/r + 1)
+	}
+	return int64(d / r)
+}
+
+// TODO(zhaoq): It is the simplistic and not bandwidth efficient. Improve it.
+func encodeTimeout(t time.Duration) string {
+	if t <= 0 {
+		return "0n"
+	}
+	if d := div(t, time.Nanosecond); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "n"
+	}
+	if d := div(t, time.Microsecond); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "u"
+	}
+	if d := div(t, time.Millisecond); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "m"
+	}
+	if d := div(t, time.Second); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "S"
+	}
+	if d := div(t, time.Minute); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "M"
+	}
+	// Note that maxTimeoutValue * time.Hour > MaxInt64.
+	return strconv.FormatInt(div(t, time.Hour), 10) + "H"
+}
+
+func decodeTimeout(s string) (time.Duration, error) {
+	size := len(s)
+	if size < 2 {
+		return 0, fmt.Errorf("transport: timeout string is too short: %q", s)
+	}
+	if size > 9 {
+		// Spec allows for 8 digits plus the unit.
+		return 0, fmt.Errorf("transport: timeout string is too long: %q", s)
+	}
+	unit := timeoutUnit(s[size-1])
+	d, ok := timeoutUnitToDuration(unit)
+	if !ok {
+		return 0, fmt.Errorf("transport: timeout unit is not recognized: %q", s)
+	}
+	t, err := strconv.ParseInt(s[:size-1], 10, 64)
+	if err != nil {
+		return 0, err
+	}
+	const maxHours = math.MaxInt64 / int64(time.Hour)
+	if d == time.Hour && t > maxHours {
+		// This timeout would overflow math.MaxInt64; clamp it.
+		return time.Duration(math.MaxInt64), nil
+	}
+	return d * time.Duration(t), nil
+}
+
+const (
+	spaceByte   = ' '
+	tildeByte   = '~'
+	percentByte = '%'
+)
+
+// encodeGrpcMessage is used to encode status code in header field
+// "grpc-message". It does percent encoding and also replaces invalid utf-8
+// characters with Unicode replacement character.
+//
+// It checks to see if each individual byte in msg is an allowable byte, and
+// then either percent encoding or passing it through. When percent encoding,
+// the byte is converted into hexadecimal notation with a '%' prepended.
+func encodeGrpcMessage(msg string) string {
+	if msg == "" {
+		return ""
+	}
+	lenMsg := len(msg)
+	for i := 0; i < lenMsg; i++ {
+		c := msg[i]
+		if !(c >= spaceByte && c <= tildeByte && c != percentByte) {
+			return encodeGrpcMessageUnchecked(msg)
+		}
+	}
+	return msg
+}
+
+func encodeGrpcMessageUnchecked(msg string) string {
+	var buf bytes.Buffer
+	for len(msg) > 0 {
+		r, size := utf8.DecodeRuneInString(msg)
+		for _, b := range []byte(string(r)) {
+			if size > 1 {
+				// If size > 1, r is not ascii. Always do percent encoding.
+				buf.WriteString(fmt.Sprintf("%%%02X", b))
+				continue
+			}
+
+			// The for loop is necessary even if size == 1. r could be
+			// utf8.RuneError.
+			//
+			// fmt.Sprintf("%%%02X", utf8.RuneError) gives "%FFFD".
+			if b >= spaceByte && b <= tildeByte && b != percentByte {
+				buf.WriteByte(b)
+			} else {
+				buf.WriteString(fmt.Sprintf("%%%02X", b))
+			}
+		}
+		msg = msg[size:]
+	}
+	return buf.String()
+}
+
+// decodeGrpcMessage decodes the msg encoded by encodeGrpcMessage.
+func decodeGrpcMessage(msg string) string {
+	if msg == "" {
+		return ""
+	}
+	lenMsg := len(msg)
+	for i := 0; i < lenMsg; i++ {
+		if msg[i] == percentByte && i+2 < lenMsg {
+			return decodeGrpcMessageUnchecked(msg)
+		}
+	}
+	return msg
+}
+
+func decodeGrpcMessageUnchecked(msg string) string {
+	var buf bytes.Buffer
+	lenMsg := len(msg)
+	for i := 0; i < lenMsg; i++ {
+		c := msg[i]
+		if c == percentByte && i+2 < lenMsg {
+			parsed, err := strconv.ParseUint(msg[i+1:i+3], 16, 8)
+			if err != nil {
+				buf.WriteByte(c)
+			} else {
+				buf.WriteByte(byte(parsed))
+				i += 2
+			}
+		} else {
+			buf.WriteByte(c)
+		}
+	}
+	return buf.String()
+}
+
+type bufWriter struct {
+	buf       []byte
+	offset    int
+	batchSize int
+	conn      net.Conn
+	err       error
+
+	onFlush func()
+}
+
+func newBufWriter(conn net.Conn, batchSize int) *bufWriter {
+	return &bufWriter{
+		buf:       make([]byte, batchSize*2),
+		batchSize: batchSize,
+		conn:      conn,
+	}
+}
+
+func (w *bufWriter) Write(b []byte) (n int, err error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+	if w.batchSize == 0 { // Buffer has been disabled.
+		return w.conn.Write(b)
+	}
+	for len(b) > 0 {
+		nn := copy(w.buf[w.offset:], b)
+		b = b[nn:]
+		w.offset += nn
+		n += nn
+		if w.offset >= w.batchSize {
+			err = w.Flush()
+		}
+	}
+	return n, err
+}
+
+func (w *bufWriter) Flush() error {
+	if w.err != nil {
+		return w.err
+	}
+	if w.offset == 0 {
+		return nil
+	}
+	if w.onFlush != nil {
+		w.onFlush()
+	}
+	_, w.err = w.conn.Write(w.buf[:w.offset])
+	w.offset = 0
+	return w.err
+}
+
+type framer struct {
+	writer *bufWriter
+	fr     *http2.Framer
+}
+
+func newFramer(conn net.Conn, writeBufferSize, readBufferSize int, maxHeaderListSize uint32) *framer {
+	if writeBufferSize < 0 {
+		writeBufferSize = 0
+	}
+	var r io.Reader = conn
+	if readBufferSize > 0 {
+		r = bufio.NewReaderSize(r, readBufferSize)
+	}
+	w := newBufWriter(conn, writeBufferSize)
+	f := &framer{
+		writer: w,
+		fr:     http2.NewFramer(w, r),
+	}
+	// Opt-in to Frame reuse API on framer to reduce garbage.
+	// Frames aren't safe to read from after a subsequent call to ReadFrame.
+	f.fr.SetReuseFrames()
+	f.fr.MaxHeaderListSize = maxHeaderListSize
+	f.fr.ReadMetaHeaders = hpack.NewDecoder(http2InitHeaderTableSize, nil)
+	return f
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/log.go b/go/vendor/google.golang.org/grpc/internal/transport/log.go
new file mode 100644
index 0000000..879df80
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/log.go
@@ -0,0 +1,44 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// This file contains wrappers for grpclog functions.
+// The transport package only logs to verbose level 2 by default.
+
+package transport
+
+import "google.golang.org/grpc/grpclog"
+
+const logLevel = 2
+
+func infof(format string, args ...interface{}) {
+	if grpclog.V(logLevel) {
+		grpclog.Infof(format, args...)
+	}
+}
+
+func warningf(format string, args ...interface{}) {
+	if grpclog.V(logLevel) {
+		grpclog.Warningf(format, args...)
+	}
+}
+
+func errorf(format string, args ...interface{}) {
+	if grpclog.V(logLevel) {
+		grpclog.Errorf(format, args...)
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/internal/transport/transport.go b/go/vendor/google.golang.org/grpc/internal/transport/transport.go
new file mode 100644
index 0000000..1be518a
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/internal/transport/transport.go
@@ -0,0 +1,712 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package transport defines and implements message oriented communication
+// channel to complete various transactions (e.g., an RPC).  It is meant for
+// grpc-internal usage and is not intended to be imported directly by users.
+package transport
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"sync"
+	"sync/atomic"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/tap"
+)
+
+// recvMsg represents the received msg from the transport. All transport
+// protocol specific info has been removed.
+type recvMsg struct {
+	data []byte
+	// nil: received some data
+	// io.EOF: stream is completed. data is nil.
+	// other non-nil error: transport failure. data is nil.
+	err error
+}
+
+// recvBuffer is an unbounded channel of recvMsg structs.
+// Note recvBuffer differs from controlBuffer only in that recvBuffer
+// holds a channel of only recvMsg structs instead of objects implementing "item" interface.
+// recvBuffer is written to much more often than
+// controlBuffer and using strict recvMsg structs helps avoid allocation in "recvBuffer.put"
+type recvBuffer struct {
+	c       chan recvMsg
+	mu      sync.Mutex
+	backlog []recvMsg
+	err     error
+}
+
+func newRecvBuffer() *recvBuffer {
+	b := &recvBuffer{
+		c: make(chan recvMsg, 1),
+	}
+	return b
+}
+
+func (b *recvBuffer) put(r recvMsg) {
+	b.mu.Lock()
+	if b.err != nil {
+		b.mu.Unlock()
+		// An error had occurred earlier, don't accept more
+		// data or errors.
+		return
+	}
+	b.err = r.err
+	if len(b.backlog) == 0 {
+		select {
+		case b.c <- r:
+			b.mu.Unlock()
+			return
+		default:
+		}
+	}
+	b.backlog = append(b.backlog, r)
+	b.mu.Unlock()
+}
+
+func (b *recvBuffer) load() {
+	b.mu.Lock()
+	if len(b.backlog) > 0 {
+		select {
+		case b.c <- b.backlog[0]:
+			b.backlog[0] = recvMsg{}
+			b.backlog = b.backlog[1:]
+		default:
+		}
+	}
+	b.mu.Unlock()
+}
+
+// get returns the channel that receives a recvMsg in the buffer.
+//
+// Upon receipt of a recvMsg, the caller should call load to send another
+// recvMsg onto the channel if there is any.
+func (b *recvBuffer) get() <-chan recvMsg {
+	return b.c
+}
+
+//
+// recvBufferReader implements io.Reader interface to read the data from
+// recvBuffer.
+type recvBufferReader struct {
+	ctx     context.Context
+	ctxDone <-chan struct{} // cache of ctx.Done() (for performance).
+	recv    *recvBuffer
+	last    []byte // Stores the remaining data in the previous calls.
+	err     error
+}
+
+// Read reads the next len(p) bytes from last. If last is drained, it tries to
+// read additional data from recv. It blocks if there no additional data available
+// in recv. If Read returns any non-nil error, it will continue to return that error.
+func (r *recvBufferReader) Read(p []byte) (n int, err error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+	n, r.err = r.read(p)
+	return n, r.err
+}
+
+func (r *recvBufferReader) read(p []byte) (n int, err error) {
+	if r.last != nil && len(r.last) > 0 {
+		// Read remaining data left in last call.
+		copied := copy(p, r.last)
+		r.last = r.last[copied:]
+		return copied, nil
+	}
+	select {
+	case <-r.ctxDone:
+		return 0, ContextErr(r.ctx.Err())
+	case m := <-r.recv.get():
+		r.recv.load()
+		if m.err != nil {
+			return 0, m.err
+		}
+		copied := copy(p, m.data)
+		r.last = m.data[copied:]
+		return copied, nil
+	}
+}
+
+type streamState uint32
+
+const (
+	streamActive    streamState = iota
+	streamWriteDone             // EndStream sent
+	streamReadDone              // EndStream received
+	streamDone                  // the entire stream is finished.
+)
+
+// Stream represents an RPC in the transport layer.
+type Stream struct {
+	id           uint32
+	st           ServerTransport    // nil for client side Stream
+	ctx          context.Context    // the associated context of the stream
+	cancel       context.CancelFunc // always nil for client side Stream
+	done         chan struct{}      // closed at the end of stream to unblock writers. On the client side.
+	ctxDone      <-chan struct{}    // same as done chan but for server side. Cache of ctx.Done() (for performance)
+	method       string             // the associated RPC method of the stream
+	recvCompress string
+	sendCompress string
+	buf          *recvBuffer
+	trReader     io.Reader
+	fc           *inFlow
+	wq           *writeQuota
+
+	// Callback to state application's intentions to read data. This
+	// is used to adjust flow control, if needed.
+	requestRead func(int)
+
+	headerChan chan struct{} // closed to indicate the end of header metadata.
+	headerDone uint32        // set when headerChan is closed. Used to avoid closing headerChan multiple times.
+
+	// hdrMu protects header and trailer metadata on the server-side.
+	hdrMu   sync.Mutex
+	header  metadata.MD // the received header metadata.
+	trailer metadata.MD // the key-value map of trailer metadata.
+
+	noHeaders bool // set if the client never received headers (set only after the stream is done).
+
+	// On the server-side, headerSent is atomically set to 1 when the headers are sent out.
+	headerSent uint32
+
+	state streamState
+
+	// On client-side it is the status error received from the server.
+	// On server-side it is unused.
+	status *status.Status
+
+	bytesReceived uint32 // indicates whether any bytes have been received on this stream
+	unprocessed   uint32 // set if the server sends a refused stream or GOAWAY including this stream
+
+	// contentSubtype is the content-subtype for requests.
+	// this must be lowercase or the behavior is undefined.
+	contentSubtype string
+}
+
+// isHeaderSent is only valid on the server-side.
+func (s *Stream) isHeaderSent() bool {
+	return atomic.LoadUint32(&s.headerSent) == 1
+}
+
+// updateHeaderSent updates headerSent and returns true
+// if it was alreay set. It is valid only on server-side.
+func (s *Stream) updateHeaderSent() bool {
+	return atomic.SwapUint32(&s.headerSent, 1) == 1
+}
+
+func (s *Stream) swapState(st streamState) streamState {
+	return streamState(atomic.SwapUint32((*uint32)(&s.state), uint32(st)))
+}
+
+func (s *Stream) compareAndSwapState(oldState, newState streamState) bool {
+	return atomic.CompareAndSwapUint32((*uint32)(&s.state), uint32(oldState), uint32(newState))
+}
+
+func (s *Stream) getState() streamState {
+	return streamState(atomic.LoadUint32((*uint32)(&s.state)))
+}
+
+func (s *Stream) waitOnHeader() error {
+	if s.headerChan == nil {
+		// On the server headerChan is always nil since a stream originates
+		// only after having received headers.
+		return nil
+	}
+	select {
+	case <-s.ctx.Done():
+		return ContextErr(s.ctx.Err())
+	case <-s.headerChan:
+		return nil
+	}
+}
+
+// RecvCompress returns the compression algorithm applied to the inbound
+// message. It is empty string if there is no compression applied.
+func (s *Stream) RecvCompress() string {
+	if err := s.waitOnHeader(); err != nil {
+		return ""
+	}
+	return s.recvCompress
+}
+
+// SetSendCompress sets the compression algorithm to the stream.
+func (s *Stream) SetSendCompress(str string) {
+	s.sendCompress = str
+}
+
+// Done returns a channel which is closed when it receives the final status
+// from the server.
+func (s *Stream) Done() <-chan struct{} {
+	return s.done
+}
+
+// Header acquires the key-value pairs of header metadata once it
+// is available. It blocks until i) the metadata is ready or ii) there is no
+// header metadata or iii) the stream is canceled/expired.
+func (s *Stream) Header() (metadata.MD, error) {
+	err := s.waitOnHeader()
+	// Even if the stream is closed, header is returned if available.
+	select {
+	case <-s.headerChan:
+		if s.header == nil {
+			return nil, nil
+		}
+		return s.header.Copy(), nil
+	default:
+	}
+	return nil, err
+}
+
+// TrailersOnly blocks until a header or trailers-only frame is received and
+// then returns true if the stream was trailers-only.  If the stream ends
+// before headers are received, returns true, nil.  If a context error happens
+// first, returns it as a status error.  Client-side only.
+func (s *Stream) TrailersOnly() (bool, error) {
+	err := s.waitOnHeader()
+	if err != nil {
+		return false, err
+	}
+	// if !headerDone, some other connection error occurred.
+	return s.noHeaders && atomic.LoadUint32(&s.headerDone) == 1, nil
+}
+
+// Trailer returns the cached trailer metedata. Note that if it is not called
+// after the entire stream is done, it could return an empty MD. Client
+// side only.
+// It can be safely read only after stream has ended that is either read
+// or write have returned io.EOF.
+func (s *Stream) Trailer() metadata.MD {
+	c := s.trailer.Copy()
+	return c
+}
+
+// ContentSubtype returns the content-subtype for a request. For example, a
+// content-subtype of "proto" will result in a content-type of
+// "application/grpc+proto". This will always be lowercase.  See
+// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
+// more details.
+func (s *Stream) ContentSubtype() string {
+	return s.contentSubtype
+}
+
+// Context returns the context of the stream.
+func (s *Stream) Context() context.Context {
+	return s.ctx
+}
+
+// Method returns the method for the stream.
+func (s *Stream) Method() string {
+	return s.method
+}
+
+// Status returns the status received from the server.
+// Status can be read safely only after the stream has ended,
+// that is, after Done() is closed.
+func (s *Stream) Status() *status.Status {
+	return s.status
+}
+
+// SetHeader sets the header metadata. This can be called multiple times.
+// Server side only.
+// This should not be called in parallel to other data writes.
+func (s *Stream) SetHeader(md metadata.MD) error {
+	if md.Len() == 0 {
+		return nil
+	}
+	if s.isHeaderSent() || s.getState() == streamDone {
+		return ErrIllegalHeaderWrite
+	}
+	s.hdrMu.Lock()
+	s.header = metadata.Join(s.header, md)
+	s.hdrMu.Unlock()
+	return nil
+}
+
+// SendHeader sends the given header metadata. The given metadata is
+// combined with any metadata set by previous calls to SetHeader and
+// then written to the transport stream.
+func (s *Stream) SendHeader(md metadata.MD) error {
+	return s.st.WriteHeader(s, md)
+}
+
+// SetTrailer sets the trailer metadata which will be sent with the RPC status
+// by the server. This can be called multiple times. Server side only.
+// This should not be called parallel to other data writes.
+func (s *Stream) SetTrailer(md metadata.MD) error {
+	if md.Len() == 0 {
+		return nil
+	}
+	if s.getState() == streamDone {
+		return ErrIllegalHeaderWrite
+	}
+	s.hdrMu.Lock()
+	s.trailer = metadata.Join(s.trailer, md)
+	s.hdrMu.Unlock()
+	return nil
+}
+
+func (s *Stream) write(m recvMsg) {
+	s.buf.put(m)
+}
+
+// Read reads all p bytes from the wire for this stream.
+func (s *Stream) Read(p []byte) (n int, err error) {
+	// Don't request a read if there was an error earlier
+	if er := s.trReader.(*transportReader).er; er != nil {
+		return 0, er
+	}
+	s.requestRead(len(p))
+	return io.ReadFull(s.trReader, p)
+}
+
+// tranportReader reads all the data available for this Stream from the transport and
+// passes them into the decoder, which converts them into a gRPC message stream.
+// The error is io.EOF when the stream is done or another non-nil error if
+// the stream broke.
+type transportReader struct {
+	reader io.Reader
+	// The handler to control the window update procedure for both this
+	// particular stream and the associated transport.
+	windowHandler func(int)
+	er            error
+}
+
+func (t *transportReader) Read(p []byte) (n int, err error) {
+	n, err = t.reader.Read(p)
+	if err != nil {
+		t.er = err
+		return
+	}
+	t.windowHandler(n)
+	return
+}
+
+// BytesReceived indicates whether any bytes have been received on this stream.
+func (s *Stream) BytesReceived() bool {
+	return atomic.LoadUint32(&s.bytesReceived) == 1
+}
+
+// Unprocessed indicates whether the server did not process this stream --
+// i.e. it sent a refused stream or GOAWAY including this stream ID.
+func (s *Stream) Unprocessed() bool {
+	return atomic.LoadUint32(&s.unprocessed) == 1
+}
+
+// GoString is implemented by Stream so context.String() won't
+// race when printing %#v.
+func (s *Stream) GoString() string {
+	return fmt.Sprintf("<stream: %p, %v>", s, s.method)
+}
+
+// state of transport
+type transportState int
+
+const (
+	reachable transportState = iota
+	closing
+	draining
+)
+
+// ServerConfig consists of all the configurations to establish a server transport.
+type ServerConfig struct {
+	MaxStreams            uint32
+	AuthInfo              credentials.AuthInfo
+	InTapHandle           tap.ServerInHandle
+	StatsHandler          stats.Handler
+	KeepaliveParams       keepalive.ServerParameters
+	KeepalivePolicy       keepalive.EnforcementPolicy
+	InitialWindowSize     int32
+	InitialConnWindowSize int32
+	WriteBufferSize       int
+	ReadBufferSize        int
+	ChannelzParentID      int64
+	MaxHeaderListSize     *uint32
+}
+
+// NewServerTransport creates a ServerTransport with conn or non-nil error
+// if it fails.
+func NewServerTransport(protocol string, conn net.Conn, config *ServerConfig) (ServerTransport, error) {
+	return newHTTP2Server(conn, config)
+}
+
+// ConnectOptions covers all relevant options for communicating with the server.
+type ConnectOptions struct {
+	// UserAgent is the application user agent.
+	UserAgent string
+	// Dialer specifies how to dial a network address.
+	Dialer func(context.Context, string) (net.Conn, error)
+	// FailOnNonTempDialError specifies if gRPC fails on non-temporary dial errors.
+	FailOnNonTempDialError bool
+	// PerRPCCredentials stores the PerRPCCredentials required to issue RPCs.
+	PerRPCCredentials []credentials.PerRPCCredentials
+	// TransportCredentials stores the Authenticator required to setup a client
+	// connection. Only one of TransportCredentials and CredsBundle is non-nil.
+	TransportCredentials credentials.TransportCredentials
+	// CredsBundle is the credentials bundle to be used. Only one of
+	// TransportCredentials and CredsBundle is non-nil.
+	CredsBundle credentials.Bundle
+	// KeepaliveParams stores the keepalive parameters.
+	KeepaliveParams keepalive.ClientParameters
+	// StatsHandler stores the handler for stats.
+	StatsHandler stats.Handler
+	// InitialWindowSize sets the initial window size for a stream.
+	InitialWindowSize int32
+	// InitialConnWindowSize sets the initial window size for a connection.
+	InitialConnWindowSize int32
+	// WriteBufferSize sets the size of write buffer which in turn determines how much data can be batched before it's written on the wire.
+	WriteBufferSize int
+	// ReadBufferSize sets the size of read buffer, which in turn determines how much data can be read at most for one read syscall.
+	ReadBufferSize int
+	// ChannelzParentID sets the addrConn id which initiate the creation of this client transport.
+	ChannelzParentID int64
+	// MaxHeaderListSize sets the max (uncompressed) size of header list that is prepared to be received.
+	MaxHeaderListSize *uint32
+}
+
+// TargetInfo contains the information of the target such as network address and metadata.
+type TargetInfo struct {
+	Addr      string
+	Metadata  interface{}
+	Authority string
+}
+
+// NewClientTransport establishes the transport with the required ConnectOptions
+// and returns it to the caller.
+func NewClientTransport(connectCtx, ctx context.Context, target TargetInfo, opts ConnectOptions, onSuccess func(), onGoAway func(GoAwayReason), onClose func()) (ClientTransport, error) {
+	return newHTTP2Client(connectCtx, ctx, target, opts, onSuccess, onGoAway, onClose)
+}
+
+// Options provides additional hints and information for message
+// transmission.
+type Options struct {
+	// Last indicates whether this write is the last piece for
+	// this stream.
+	Last bool
+}
+
+// CallHdr carries the information of a particular RPC.
+type CallHdr struct {
+	// Host specifies the peer's host.
+	Host string
+
+	// Method specifies the operation to perform.
+	Method string
+
+	// SendCompress specifies the compression algorithm applied on
+	// outbound message.
+	SendCompress string
+
+	// Creds specifies credentials.PerRPCCredentials for a call.
+	Creds credentials.PerRPCCredentials
+
+	// ContentSubtype specifies the content-subtype for a request. For example, a
+	// content-subtype of "proto" will result in a content-type of
+	// "application/grpc+proto". The value of ContentSubtype must be all
+	// lowercase, otherwise the behavior is undefined. See
+	// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests
+	// for more details.
+	ContentSubtype string
+
+	PreviousAttempts int // value of grpc-previous-rpc-attempts header to set
+}
+
+// ClientTransport is the common interface for all gRPC client-side transport
+// implementations.
+type ClientTransport interface {
+	// Close tears down this transport. Once it returns, the transport
+	// should not be accessed any more. The caller must make sure this
+	// is called only once.
+	Close() error
+
+	// GracefulClose starts to tear down the transport. It stops accepting
+	// new RPCs and wait the completion of the pending RPCs.
+	GracefulClose() error
+
+	// Write sends the data for the given stream. A nil stream indicates
+	// the write is to be performed on the transport as a whole.
+	Write(s *Stream, hdr []byte, data []byte, opts *Options) error
+
+	// NewStream creates a Stream for an RPC.
+	NewStream(ctx context.Context, callHdr *CallHdr) (*Stream, error)
+
+	// CloseStream clears the footprint of a stream when the stream is
+	// not needed any more. The err indicates the error incurred when
+	// CloseStream is called. Must be called when a stream is finished
+	// unless the associated transport is closing.
+	CloseStream(stream *Stream, err error)
+
+	// Error returns a channel that is closed when some I/O error
+	// happens. Typically the caller should have a goroutine to monitor
+	// this in order to take action (e.g., close the current transport
+	// and create a new one) in error case. It should not return nil
+	// once the transport is initiated.
+	Error() <-chan struct{}
+
+	// GoAway returns a channel that is closed when ClientTransport
+	// receives the draining signal from the server (e.g., GOAWAY frame in
+	// HTTP/2).
+	GoAway() <-chan struct{}
+
+	// GetGoAwayReason returns the reason why GoAway frame was received.
+	GetGoAwayReason() GoAwayReason
+
+	// IncrMsgSent increments the number of message sent through this transport.
+	IncrMsgSent()
+
+	// IncrMsgRecv increments the number of message received through this transport.
+	IncrMsgRecv()
+}
+
+// ServerTransport is the common interface for all gRPC server-side transport
+// implementations.
+//
+// Methods may be called concurrently from multiple goroutines, but
+// Write methods for a given Stream will be called serially.
+type ServerTransport interface {
+	// HandleStreams receives incoming streams using the given handler.
+	HandleStreams(func(*Stream), func(context.Context, string) context.Context)
+
+	// WriteHeader sends the header metadata for the given stream.
+	// WriteHeader may not be called on all streams.
+	WriteHeader(s *Stream, md metadata.MD) error
+
+	// Write sends the data for the given stream.
+	// Write may not be called on all streams.
+	Write(s *Stream, hdr []byte, data []byte, opts *Options) error
+
+	// WriteStatus sends the status of a stream to the client.  WriteStatus is
+	// the final call made on a stream and always occurs.
+	WriteStatus(s *Stream, st *status.Status) error
+
+	// Close tears down the transport. Once it is called, the transport
+	// should not be accessed any more. All the pending streams and their
+	// handlers will be terminated asynchronously.
+	Close() error
+
+	// RemoteAddr returns the remote network address.
+	RemoteAddr() net.Addr
+
+	// Drain notifies the client this ServerTransport stops accepting new RPCs.
+	Drain()
+
+	// IncrMsgSent increments the number of message sent through this transport.
+	IncrMsgSent()
+
+	// IncrMsgRecv increments the number of message received through this transport.
+	IncrMsgRecv()
+}
+
+// connectionErrorf creates an ConnectionError with the specified error description.
+func connectionErrorf(temp bool, e error, format string, a ...interface{}) ConnectionError {
+	return ConnectionError{
+		Desc: fmt.Sprintf(format, a...),
+		temp: temp,
+		err:  e,
+	}
+}
+
+// ConnectionError is an error that results in the termination of the
+// entire connection and the retry of all the active streams.
+type ConnectionError struct {
+	Desc string
+	temp bool
+	err  error
+}
+
+func (e ConnectionError) Error() string {
+	return fmt.Sprintf("connection error: desc = %q", e.Desc)
+}
+
+// Temporary indicates if this connection error is temporary or fatal.
+func (e ConnectionError) Temporary() bool {
+	return e.temp
+}
+
+// Origin returns the original error of this connection error.
+func (e ConnectionError) Origin() error {
+	// Never return nil error here.
+	// If the original error is nil, return itself.
+	if e.err == nil {
+		return e
+	}
+	return e.err
+}
+
+var (
+	// ErrConnClosing indicates that the transport is closing.
+	ErrConnClosing = connectionErrorf(true, nil, "transport is closing")
+	// errStreamDrain indicates that the stream is rejected because the
+	// connection is draining. This could be caused by goaway or balancer
+	// removing the address.
+	errStreamDrain = status.Error(codes.Unavailable, "the connection is draining")
+	// errStreamDone is returned from write at the client side to indiacte application
+	// layer of an error.
+	errStreamDone = errors.New("the stream is done")
+	// StatusGoAway indicates that the server sent a GOAWAY that included this
+	// stream's ID in unprocessed RPCs.
+	statusGoAway = status.New(codes.Unavailable, "the stream is rejected because server is draining the connection")
+)
+
+// GoAwayReason contains the reason for the GoAway frame received.
+type GoAwayReason uint8
+
+const (
+	// GoAwayInvalid indicates that no GoAway frame is received.
+	GoAwayInvalid GoAwayReason = 0
+	// GoAwayNoReason is the default value when GoAway frame is received.
+	GoAwayNoReason GoAwayReason = 1
+	// GoAwayTooManyPings indicates that a GoAway frame with
+	// ErrCodeEnhanceYourCalm was received and that the debug data said
+	// "too_many_pings".
+	GoAwayTooManyPings GoAwayReason = 2
+)
+
+// channelzData is used to store channelz related data for http2Client and http2Server.
+// These fields cannot be embedded in the original structs (e.g. http2Client), since to do atomic
+// operation on int64 variable on 32-bit machine, user is responsible to enforce memory alignment.
+// Here, by grouping those int64 fields inside a struct, we are enforcing the alignment.
+type channelzData struct {
+	kpCount int64
+	// The number of streams that have started, including already finished ones.
+	streamsStarted int64
+	// Client side: The number of streams that have ended successfully by receiving
+	// EoS bit set frame from server.
+	// Server side: The number of streams that have ended successfully by sending
+	// frame with EoS bit set.
+	streamsSucceeded int64
+	streamsFailed    int64
+	// lastStreamCreatedTime stores the timestamp that the last stream gets created. It is of int64 type
+	// instead of time.Time since it's more costly to atomically update time.Time variable than int64
+	// variable. The same goes for lastMsgSentTime and lastMsgRecvTime.
+	lastStreamCreatedTime int64
+	msgSent               int64
+	msgRecv               int64
+	lastMsgSentTime       int64
+	lastMsgRecvTime       int64
+}
diff --git a/go/vendor/google.golang.org/grpc/keepalive/keepalive.go b/go/vendor/google.golang.org/grpc/keepalive/keepalive.go
new file mode 100644
index 0000000..78eea1f
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/keepalive/keepalive.go
@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package keepalive defines configurable parameters for point-to-point
+// healthcheck.
+package keepalive
+
+import (
+	"time"
+)
+
+// ClientParameters is used to set keepalive parameters on the client-side.
+// These configure how the client will actively probe to notice when a
+// connection is broken and send pings so intermediaries will be aware of the
+// liveness of the connection. Make sure these parameters are set in
+// coordination with the keepalive policy on the server, as incompatible
+// settings can result in closing of connection.
+type ClientParameters struct {
+	// After a duration of this time if the client doesn't see any activity it
+	// pings the server to see if the transport is still alive.
+	Time time.Duration // The current default value is infinity.
+	// After having pinged for keepalive check, the client waits for a duration
+	// of Timeout and if no activity is seen even after that the connection is
+	// closed.
+	Timeout time.Duration // The current default value is 20 seconds.
+	// If true, client sends keepalive pings even with no active RPCs. If false,
+	// when there are no active RPCs, Time and Timeout will be ignored and no
+	// keepalive pings will be sent.
+	PermitWithoutStream bool // false by default.
+}
+
+// ServerParameters is used to set keepalive and max-age parameters on the
+// server-side.
+type ServerParameters struct {
+	// MaxConnectionIdle is a duration for the amount of time after which an
+	// idle connection would be closed by sending a GoAway. Idleness duration is
+	// defined since the most recent time the number of outstanding RPCs became
+	// zero or the connection establishment.
+	MaxConnectionIdle time.Duration // The current default value is infinity.
+	// MaxConnectionAge is a duration for the maximum amount of time a
+	// connection may exist before it will be closed by sending a GoAway. A
+	// random jitter of +/-10% will be added to MaxConnectionAge to spread out
+	// connection storms.
+	MaxConnectionAge time.Duration // The current default value is infinity.
+	// MaxConnectinoAgeGrace is an additive period after MaxConnectionAge after
+	// which the connection will be forcibly closed.
+	MaxConnectionAgeGrace time.Duration // The current default value is infinity.
+	// After a duration of this time if the server doesn't see any activity it
+	// pings the client to see if the transport is still alive.
+	Time time.Duration // The current default value is 2 hours.
+	// After having pinged for keepalive check, the server waits for a duration
+	// of Timeout and if no activity is seen even after that the connection is
+	// closed.
+	Timeout time.Duration // The current default value is 20 seconds.
+}
+
+// EnforcementPolicy is used to set keepalive enforcement policy on the
+// server-side. Server will close connection with a client that violates this
+// policy.
+type EnforcementPolicy struct {
+	// MinTime is the minimum amount of time a client should wait before sending
+	// a keepalive ping.
+	MinTime time.Duration // The current default value is 5 minutes.
+	// If true, server allows keepalive pings even when there are no active
+	// streams(RPCs). If false, and client sends ping when there are no active
+	// streams, server will send GOAWAY and close the connection.
+	PermitWithoutStream bool // false by default.
+}
diff --git a/go/vendor/google.golang.org/grpc/metadata/metadata.go b/go/vendor/google.golang.org/grpc/metadata/metadata.go
new file mode 100644
index 0000000..bd2eaf4
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/metadata/metadata.go
@@ -0,0 +1,210 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package metadata define the structure of the metadata supported by gRPC library.
+// Please refer to https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
+// for more information about custom-metadata.
+package metadata // import "google.golang.org/grpc/metadata"
+
+import (
+	"fmt"
+	"strings"
+
+	"golang.org/x/net/context"
+)
+
+// DecodeKeyValue returns k, v, nil.
+//
+// Deprecated: use k and v directly instead.
+func DecodeKeyValue(k, v string) (string, string, error) {
+	return k, v, nil
+}
+
+// MD is a mapping from metadata keys to values. Users should use the following
+// two convenience functions New and Pairs to generate MD.
+type MD map[string][]string
+
+// New creates an MD from a given key-value map.
+//
+// Only the following ASCII characters are allowed in keys:
+//  - digits: 0-9
+//  - uppercase letters: A-Z (normalized to lower)
+//  - lowercase letters: a-z
+//  - special characters: -_.
+// Uppercase letters are automatically converted to lowercase.
+//
+// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
+// result in errors if set in metadata.
+func New(m map[string]string) MD {
+	md := MD{}
+	for k, val := range m {
+		key := strings.ToLower(k)
+		md[key] = append(md[key], val)
+	}
+	return md
+}
+
+// Pairs returns an MD formed by the mapping of key, value ...
+// Pairs panics if len(kv) is odd.
+//
+// Only the following ASCII characters are allowed in keys:
+//  - digits: 0-9
+//  - uppercase letters: A-Z (normalized to lower)
+//  - lowercase letters: a-z
+//  - special characters: -_.
+// Uppercase letters are automatically converted to lowercase.
+//
+// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
+// result in errors if set in metadata.
+func Pairs(kv ...string) MD {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md := MD{}
+	var key string
+	for i, s := range kv {
+		if i%2 == 0 {
+			key = strings.ToLower(s)
+			continue
+		}
+		md[key] = append(md[key], s)
+	}
+	return md
+}
+
+// Len returns the number of items in md.
+func (md MD) Len() int {
+	return len(md)
+}
+
+// Copy returns a copy of md.
+func (md MD) Copy() MD {
+	return Join(md)
+}
+
+// Get obtains the values for a given key.
+func (md MD) Get(k string) []string {
+	k = strings.ToLower(k)
+	return md[k]
+}
+
+// Set sets the value of a given key with a slice of values.
+func (md MD) Set(k string, vals ...string) {
+	if len(vals) == 0 {
+		return
+	}
+	k = strings.ToLower(k)
+	md[k] = vals
+}
+
+// Append adds the values to key k, not overwriting what was already stored at that key.
+func (md MD) Append(k string, vals ...string) {
+	if len(vals) == 0 {
+		return
+	}
+	k = strings.ToLower(k)
+	md[k] = append(md[k], vals...)
+}
+
+// Join joins any number of mds into a single MD.
+// The order of values for each key is determined by the order in which
+// the mds containing those values are presented to Join.
+func Join(mds ...MD) MD {
+	out := MD{}
+	for _, md := range mds {
+		for k, v := range md {
+			out[k] = append(out[k], v...)
+		}
+	}
+	return out
+}
+
+type mdIncomingKey struct{}
+type mdOutgoingKey struct{}
+
+// NewIncomingContext creates a new context with incoming md attached.
+func NewIncomingContext(ctx context.Context, md MD) context.Context {
+	return context.WithValue(ctx, mdIncomingKey{}, md)
+}
+
+// NewOutgoingContext creates a new context with outgoing md attached. If used
+// in conjunction with AppendToOutgoingContext, NewOutgoingContext will
+// overwrite any previously-appended metadata.
+func NewOutgoingContext(ctx context.Context, md MD) context.Context {
+	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md})
+}
+
+// AppendToOutgoingContext returns a new context with the provided kv merged
+// with any existing metadata in the context. Please refer to the
+// documentation of Pairs for a description of kv.
+func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md, _ := ctx.Value(mdOutgoingKey{}).(rawMD)
+	added := make([][]string, len(md.added)+1)
+	copy(added, md.added)
+	added[len(added)-1] = make([]string, len(kv))
+	copy(added[len(added)-1], kv)
+	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md.md, added: added})
+}
+
+// FromIncomingContext returns the incoming metadata in ctx if it exists.  The
+// returned MD should not be modified. Writing to it may cause races.
+// Modification should be made to copies of the returned MD.
+func FromIncomingContext(ctx context.Context) (md MD, ok bool) {
+	md, ok = ctx.Value(mdIncomingKey{}).(MD)
+	return
+}
+
+// FromOutgoingContextRaw returns the un-merged, intermediary contents
+// of rawMD. Remember to perform strings.ToLower on the keys. The returned
+// MD should not be modified. Writing to it may cause races. Modification
+// should be made to copies of the returned MD.
+//
+// This is intended for gRPC-internal use ONLY.
+func FromOutgoingContextRaw(ctx context.Context) (MD, [][]string, bool) {
+	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
+	if !ok {
+		return nil, nil, false
+	}
+
+	return raw.md, raw.added, true
+}
+
+// FromOutgoingContext returns the outgoing metadata in ctx if it exists.  The
+// returned MD should not be modified. Writing to it may cause races.
+// Modification should be made to copies of the returned MD.
+func FromOutgoingContext(ctx context.Context) (MD, bool) {
+	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
+	if !ok {
+		return nil, false
+	}
+
+	mds := make([]MD, 0, len(raw.added)+1)
+	mds = append(mds, raw.md)
+	for _, vv := range raw.added {
+		mds = append(mds, Pairs(vv...))
+	}
+	return Join(mds...), ok
+}
+
+type rawMD struct {
+	md    MD
+	added [][]string
+}
diff --git a/go/vendor/google.golang.org/grpc/naming/dns_resolver.go b/go/vendor/google.golang.org/grpc/naming/dns_resolver.go
new file mode 100644
index 0000000..0f8a908
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/naming/dns_resolver.go
@@ -0,0 +1,290 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package naming
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"strconv"
+	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/grpclog"
+)
+
+const (
+	defaultPort = "443"
+	defaultFreq = time.Minute * 30
+)
+
+var (
+	errMissingAddr  = errors.New("missing address")
+	errWatcherClose = errors.New("watcher has been closed")
+)
+
+// NewDNSResolverWithFreq creates a DNS Resolver that can resolve DNS names, and
+// create watchers that poll the DNS server using the frequency set by freq.
+func NewDNSResolverWithFreq(freq time.Duration) (Resolver, error) {
+	return &dnsResolver{freq: freq}, nil
+}
+
+// NewDNSResolver creates a DNS Resolver that can resolve DNS names, and create
+// watchers that poll the DNS server using the default frequency defined by defaultFreq.
+func NewDNSResolver() (Resolver, error) {
+	return NewDNSResolverWithFreq(defaultFreq)
+}
+
+// dnsResolver handles name resolution for names following the DNS scheme
+type dnsResolver struct {
+	// frequency of polling the DNS server that the watchers created by this resolver will use.
+	freq time.Duration
+}
+
+// formatIP returns ok = false if addr is not a valid textual representation of an IP address.
+// If addr is an IPv4 address, return the addr and ok = true.
+// If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true.
+func formatIP(addr string) (addrIP string, ok bool) {
+	ip := net.ParseIP(addr)
+	if ip == nil {
+		return "", false
+	}
+	if ip.To4() != nil {
+		return addr, true
+	}
+	return "[" + addr + "]", true
+}
+
+// parseTarget takes the user input target string, returns formatted host and port info.
+// If target doesn't specify a port, set the port to be the defaultPort.
+// If target is in IPv6 format and host-name is enclosed in sqarue brackets, brackets
+// are strippd when setting the host.
+// examples:
+// target: "www.google.com" returns host: "www.google.com", port: "443"
+// target: "ipv4-host:80" returns host: "ipv4-host", port: "80"
+// target: "[ipv6-host]" returns host: "ipv6-host", port: "443"
+// target: ":80" returns host: "localhost", port: "80"
+// target: ":" returns host: "localhost", port: "443"
+func parseTarget(target string) (host, port string, err error) {
+	if target == "" {
+		return "", "", errMissingAddr
+	}
+
+	if ip := net.ParseIP(target); ip != nil {
+		// target is an IPv4 or IPv6(without brackets) address
+		return target, defaultPort, nil
+	}
+	if host, port, err := net.SplitHostPort(target); err == nil {
+		// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
+		if host == "" {
+			// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
+			host = "localhost"
+		}
+		if port == "" {
+			// If the port field is empty(target ends with colon), e.g. "[::1]:", defaultPort is used.
+			port = defaultPort
+		}
+		return host, port, nil
+	}
+	if host, port, err := net.SplitHostPort(target + ":" + defaultPort); err == nil {
+		// target doesn't have port
+		return host, port, nil
+	}
+	return "", "", fmt.Errorf("invalid target address %v", target)
+}
+
+// Resolve creates a watcher that watches the name resolution of the target.
+func (r *dnsResolver) Resolve(target string) (Watcher, error) {
+	host, port, err := parseTarget(target)
+	if err != nil {
+		return nil, err
+	}
+
+	if net.ParseIP(host) != nil {
+		ipWatcher := &ipWatcher{
+			updateChan: make(chan *Update, 1),
+		}
+		host, _ = formatIP(host)
+		ipWatcher.updateChan <- &Update{Op: Add, Addr: host + ":" + port}
+		return ipWatcher, nil
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	return &dnsWatcher{
+		r:      r,
+		host:   host,
+		port:   port,
+		ctx:    ctx,
+		cancel: cancel,
+		t:      time.NewTimer(0),
+	}, nil
+}
+
+// dnsWatcher watches for the name resolution update for a specific target
+type dnsWatcher struct {
+	r    *dnsResolver
+	host string
+	port string
+	// The latest resolved address set
+	curAddrs map[string]*Update
+	ctx      context.Context
+	cancel   context.CancelFunc
+	t        *time.Timer
+}
+
+// ipWatcher watches for the name resolution update for an IP address.
+type ipWatcher struct {
+	updateChan chan *Update
+}
+
+// Next returns the address resolution Update for the target. For IP address,
+// the resolution is itself, thus polling name server is unnecessary. Therefore,
+// Next() will return an Update the first time it is called, and will be blocked
+// for all following calls as no Update exists until watcher is closed.
+func (i *ipWatcher) Next() ([]*Update, error) {
+	u, ok := <-i.updateChan
+	if !ok {
+		return nil, errWatcherClose
+	}
+	return []*Update{u}, nil
+}
+
+// Close closes the ipWatcher.
+func (i *ipWatcher) Close() {
+	close(i.updateChan)
+}
+
+// AddressType indicates the address type returned by name resolution.
+type AddressType uint8
+
+const (
+	// Backend indicates the server is a backend server.
+	Backend AddressType = iota
+	// GRPCLB indicates the server is a grpclb load balancer.
+	GRPCLB
+)
+
+// AddrMetadataGRPCLB contains the information the name resolver for grpclb should provide. The
+// name resolver used by the grpclb balancer is required to provide this type of metadata in
+// its address updates.
+type AddrMetadataGRPCLB struct {
+	// AddrType is the type of server (grpc load balancer or backend).
+	AddrType AddressType
+	// ServerName is the name of the grpc load balancer. Used for authentication.
+	ServerName string
+}
+
+// compileUpdate compares the old resolved addresses and newly resolved addresses,
+// and generates an update list
+func (w *dnsWatcher) compileUpdate(newAddrs map[string]*Update) []*Update {
+	var res []*Update
+	for a, u := range w.curAddrs {
+		if _, ok := newAddrs[a]; !ok {
+			u.Op = Delete
+			res = append(res, u)
+		}
+	}
+	for a, u := range newAddrs {
+		if _, ok := w.curAddrs[a]; !ok {
+			res = append(res, u)
+		}
+	}
+	return res
+}
+
+func (w *dnsWatcher) lookupSRV() map[string]*Update {
+	newAddrs := make(map[string]*Update)
+	_, srvs, err := lookupSRV(w.ctx, "grpclb", "tcp", w.host)
+	if err != nil {
+		grpclog.Infof("grpc: failed dns SRV record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, s := range srvs {
+		lbAddrs, err := lookupHost(w.ctx, s.Target)
+		if err != nil {
+			grpclog.Warningf("grpc: failed load banlacer address dns lookup due to %v.\n", err)
+			continue
+		}
+		for _, a := range lbAddrs {
+			a, ok := formatIP(a)
+			if !ok {
+				grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+				continue
+			}
+			addr := a + ":" + strconv.Itoa(int(s.Port))
+			newAddrs[addr] = &Update{Addr: addr,
+				Metadata: AddrMetadataGRPCLB{AddrType: GRPCLB, ServerName: s.Target}}
+		}
+	}
+	return newAddrs
+}
+
+func (w *dnsWatcher) lookupHost() map[string]*Update {
+	newAddrs := make(map[string]*Update)
+	addrs, err := lookupHost(w.ctx, w.host)
+	if err != nil {
+		grpclog.Warningf("grpc: failed dns A record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, a := range addrs {
+		a, ok := formatIP(a)
+		if !ok {
+			grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+			continue
+		}
+		addr := a + ":" + w.port
+		newAddrs[addr] = &Update{Addr: addr}
+	}
+	return newAddrs
+}
+
+func (w *dnsWatcher) lookup() []*Update {
+	newAddrs := w.lookupSRV()
+	if newAddrs == nil {
+		// If failed to get any balancer address (either no corresponding SRV for the
+		// target, or caused by failure during resolution/parsing of the balancer target),
+		// return any A record info available.
+		newAddrs = w.lookupHost()
+	}
+	result := w.compileUpdate(newAddrs)
+	w.curAddrs = newAddrs
+	return result
+}
+
+// Next returns the resolved address update(delta) for the target. If there's no
+// change, it will sleep for 30 mins and try to resolve again after that.
+func (w *dnsWatcher) Next() ([]*Update, error) {
+	for {
+		select {
+		case <-w.ctx.Done():
+			return nil, errWatcherClose
+		case <-w.t.C:
+		}
+		result := w.lookup()
+		// Next lookup should happen after an interval defined by w.r.freq.
+		w.t.Reset(w.r.freq)
+		if len(result) > 0 {
+			return result, nil
+		}
+	}
+}
+
+func (w *dnsWatcher) Close() {
+	w.cancel()
+}
diff --git a/go/vendor/google.golang.org/grpc/naming/go17.go b/go/vendor/google.golang.org/grpc/naming/go17.go
new file mode 100644
index 0000000..57b65d7
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/naming/go17.go
@@ -0,0 +1,34 @@
+// +build go1.6,!go1.8
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package naming
+
+import (
+	"net"
+
+	"golang.org/x/net/context"
+)
+
+var (
+	lookupHost = func(ctx context.Context, host string) ([]string, error) { return net.LookupHost(host) }
+	lookupSRV  = func(ctx context.Context, service, proto, name string) (string, []*net.SRV, error) {
+		return net.LookupSRV(service, proto, name)
+	}
+)
diff --git a/go/vendor/google.golang.org/grpc/naming/go18.go b/go/vendor/google.golang.org/grpc/naming/go18.go
new file mode 100644
index 0000000..b5a0f84
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/naming/go18.go
@@ -0,0 +1,28 @@
+// +build go1.8
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package naming
+
+import "net"
+
+var (
+	lookupHost = net.DefaultResolver.LookupHost
+	lookupSRV  = net.DefaultResolver.LookupSRV
+)
diff --git a/go/vendor/google.golang.org/grpc/naming/naming.go b/go/vendor/google.golang.org/grpc/naming/naming.go
new file mode 100644
index 0000000..8cc39e9
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/naming/naming.go
@@ -0,0 +1,69 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package naming defines the naming API and related data structures for gRPC.
+// The interface is EXPERIMENTAL and may be suject to change.
+//
+// Deprecated: please use package resolver.
+package naming
+
+// Operation defines the corresponding operations for a name resolution change.
+//
+// Deprecated: please use package resolver.
+type Operation uint8
+
+const (
+	// Add indicates a new address is added.
+	Add Operation = iota
+	// Delete indicates an existing address is deleted.
+	Delete
+)
+
+// Update defines a name resolution update. Notice that it is not valid having both
+// empty string Addr and nil Metadata in an Update.
+//
+// Deprecated: please use package resolver.
+type Update struct {
+	// Op indicates the operation of the update.
+	Op Operation
+	// Addr is the updated address. It is empty string if there is no address update.
+	Addr string
+	// Metadata is the updated metadata. It is nil if there is no metadata update.
+	// Metadata is not required for a custom naming implementation.
+	Metadata interface{}
+}
+
+// Resolver creates a Watcher for a target to track its resolution changes.
+//
+// Deprecated: please use package resolver.
+type Resolver interface {
+	// Resolve creates a Watcher for target.
+	Resolve(target string) (Watcher, error)
+}
+
+// Watcher watches for the updates on the specified target.
+//
+// Deprecated: please use package resolver.
+type Watcher interface {
+	// Next blocks until an update or error happens. It may return one or more
+	// updates. The first call should get the full set of the results. It should
+	// return an error if and only if Watcher cannot recover.
+	Next() ([]*Update, error)
+	// Close closes the Watcher.
+	Close()
+}
diff --git a/go/vendor/google.golang.org/grpc/peer/peer.go b/go/vendor/google.golang.org/grpc/peer/peer.go
new file mode 100644
index 0000000..317b8b9
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/peer/peer.go
@@ -0,0 +1,51 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package peer defines various peer information associated with RPCs and
+// corresponding utils.
+package peer
+
+import (
+	"net"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/credentials"
+)
+
+// Peer contains the information of the peer for an RPC, such as the address
+// and authentication information.
+type Peer struct {
+	// Addr is the peer address.
+	Addr net.Addr
+	// AuthInfo is the authentication information of the transport.
+	// It is nil if there is no transport security being used.
+	AuthInfo credentials.AuthInfo
+}
+
+type peerKey struct{}
+
+// NewContext creates a new context with peer information attached.
+func NewContext(ctx context.Context, p *Peer) context.Context {
+	return context.WithValue(ctx, peerKey{}, p)
+}
+
+// FromContext returns the peer information in ctx if it exists.
+func FromContext(ctx context.Context) (p *Peer, ok bool) {
+	p, ok = ctx.Value(peerKey{}).(*Peer)
+	return
+}
diff --git a/go/vendor/google.golang.org/grpc/picker_wrapper.go b/go/vendor/google.golang.org/grpc/picker_wrapper.go
new file mode 100644
index 0000000..76cc456
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/picker_wrapper.go
@@ -0,0 +1,180 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"io"
+	"sync"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/status"
+)
+
+// pickerWrapper is a wrapper of balancer.Picker. It blocks on certain pick
+// actions and unblock when there's a picker update.
+type pickerWrapper struct {
+	mu         sync.Mutex
+	done       bool
+	blockingCh chan struct{}
+	picker     balancer.Picker
+
+	// The latest connection happened.
+	connErrMu sync.Mutex
+	connErr   error
+}
+
+func newPickerWrapper() *pickerWrapper {
+	bp := &pickerWrapper{blockingCh: make(chan struct{})}
+	return bp
+}
+
+func (bp *pickerWrapper) updateConnectionError(err error) {
+	bp.connErrMu.Lock()
+	bp.connErr = err
+	bp.connErrMu.Unlock()
+}
+
+func (bp *pickerWrapper) connectionError() error {
+	bp.connErrMu.Lock()
+	err := bp.connErr
+	bp.connErrMu.Unlock()
+	return err
+}
+
+// updatePicker is called by UpdateBalancerState. It unblocks all blocked pick.
+func (bp *pickerWrapper) updatePicker(p balancer.Picker) {
+	bp.mu.Lock()
+	if bp.done {
+		bp.mu.Unlock()
+		return
+	}
+	bp.picker = p
+	// bp.blockingCh should never be nil.
+	close(bp.blockingCh)
+	bp.blockingCh = make(chan struct{})
+	bp.mu.Unlock()
+}
+
+func doneChannelzWrapper(acw *acBalancerWrapper, done func(balancer.DoneInfo)) func(balancer.DoneInfo) {
+	acw.mu.Lock()
+	ac := acw.ac
+	acw.mu.Unlock()
+	ac.incrCallsStarted()
+	return func(b balancer.DoneInfo) {
+		if b.Err != nil && b.Err != io.EOF {
+			ac.incrCallsFailed()
+		} else {
+			ac.incrCallsSucceeded()
+		}
+		if done != nil {
+			done(b)
+		}
+	}
+}
+
+// pick returns the transport that will be used for the RPC.
+// It may block in the following cases:
+// - there's no picker
+// - the current picker returns ErrNoSubConnAvailable
+// - the current picker returns other errors and failfast is false.
+// - the subConn returned by the current picker is not READY
+// When one of these situations happens, pick blocks until the picker gets updated.
+func (bp *pickerWrapper) pick(ctx context.Context, failfast bool, opts balancer.PickOptions) (transport.ClientTransport, func(balancer.DoneInfo), error) {
+	var (
+		p  balancer.Picker
+		ch chan struct{}
+	)
+
+	for {
+		bp.mu.Lock()
+		if bp.done {
+			bp.mu.Unlock()
+			return nil, nil, ErrClientConnClosing
+		}
+
+		if bp.picker == nil {
+			ch = bp.blockingCh
+		}
+		if ch == bp.blockingCh {
+			// This could happen when either:
+			// - bp.picker is nil (the previous if condition), or
+			// - has called pick on the current picker.
+			bp.mu.Unlock()
+			select {
+			case <-ctx.Done():
+				return nil, nil, ctx.Err()
+			case <-ch:
+			}
+			continue
+		}
+
+		ch = bp.blockingCh
+		p = bp.picker
+		bp.mu.Unlock()
+
+		subConn, done, err := p.Pick(ctx, opts)
+
+		if err != nil {
+			switch err {
+			case balancer.ErrNoSubConnAvailable:
+				continue
+			case balancer.ErrTransientFailure:
+				if !failfast {
+					continue
+				}
+				return nil, nil, status.Errorf(codes.Unavailable, "%v, latest connection error: %v", err, bp.connectionError())
+			default:
+				// err is some other error.
+				return nil, nil, toRPCErr(err)
+			}
+		}
+
+		acw, ok := subConn.(*acBalancerWrapper)
+		if !ok {
+			grpclog.Infof("subconn returned from pick is not *acBalancerWrapper")
+			continue
+		}
+		if t, ok := acw.getAddrConn().getReadyTransport(); ok {
+			if channelz.IsOn() {
+				return t, doneChannelzWrapper(acw, done), nil
+			}
+			return t, done, nil
+		}
+		grpclog.Infof("blockingPicker: the picked transport is not ready, loop back to repick")
+		// If ok == false, ac.state is not READY.
+		// A valid picker always returns READY subConn. This means the state of ac
+		// just changed, and picker will be updated shortly.
+		// continue back to the beginning of the for loop to repick.
+	}
+}
+
+func (bp *pickerWrapper) close() {
+	bp.mu.Lock()
+	defer bp.mu.Unlock()
+	if bp.done {
+		return
+	}
+	bp.done = true
+	close(bp.blockingCh)
+}
diff --git a/go/vendor/google.golang.org/grpc/pickfirst.go b/go/vendor/google.golang.org/grpc/pickfirst.go
new file mode 100644
index 0000000..bda4309
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/pickfirst.go
@@ -0,0 +1,109 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+)
+
+// PickFirstBalancerName is the name of the pick_first balancer.
+const PickFirstBalancerName = "pick_first"
+
+func newPickfirstBuilder() balancer.Builder {
+	return &pickfirstBuilder{}
+}
+
+type pickfirstBuilder struct{}
+
+func (*pickfirstBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
+	return &pickfirstBalancer{cc: cc}
+}
+
+func (*pickfirstBuilder) Name() string {
+	return PickFirstBalancerName
+}
+
+type pickfirstBalancer struct {
+	cc balancer.ClientConn
+	sc balancer.SubConn
+}
+
+func (b *pickfirstBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
+	if err != nil {
+		grpclog.Infof("pickfirstBalancer: HandleResolvedAddrs called with error %v", err)
+		return
+	}
+	if b.sc == nil {
+		b.sc, err = b.cc.NewSubConn(addrs, balancer.NewSubConnOptions{})
+		if err != nil {
+			//TODO(yuxuanli): why not change the cc state to Idle?
+			grpclog.Errorf("pickfirstBalancer: failed to NewSubConn: %v", err)
+			return
+		}
+		b.cc.UpdateBalancerState(connectivity.Idle, &picker{sc: b.sc})
+		b.sc.Connect()
+	} else {
+		b.sc.UpdateAddresses(addrs)
+		b.sc.Connect()
+	}
+}
+
+func (b *pickfirstBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+	grpclog.Infof("pickfirstBalancer: HandleSubConnStateChange: %p, %v", sc, s)
+	if b.sc != sc {
+		grpclog.Infof("pickfirstBalancer: ignored state change because sc is not recognized")
+		return
+	}
+	if s == connectivity.Shutdown {
+		b.sc = nil
+		return
+	}
+
+	switch s {
+	case connectivity.Ready, connectivity.Idle:
+		b.cc.UpdateBalancerState(s, &picker{sc: sc})
+	case connectivity.Connecting:
+		b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrNoSubConnAvailable})
+	case connectivity.TransientFailure:
+		b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrTransientFailure})
+	}
+}
+
+func (b *pickfirstBalancer) Close() {
+}
+
+type picker struct {
+	err error
+	sc  balancer.SubConn
+}
+
+func (p *picker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	if p.err != nil {
+		return nil, nil, p.err
+	}
+	return p.sc, nil, nil
+}
+
+func init() {
+	balancer.Register(newPickfirstBuilder())
+}
diff --git a/go/vendor/google.golang.org/grpc/proxy.go b/go/vendor/google.golang.org/grpc/proxy.go
new file mode 100644
index 0000000..2d40236
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/proxy.go
@@ -0,0 +1,130 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+
+	"golang.org/x/net/context"
+)
+
+var (
+	// errDisabled indicates that proxy is disabled for the address.
+	errDisabled = errors.New("proxy is disabled for the address")
+	// The following variable will be overwritten in the tests.
+	httpProxyFromEnvironment = http.ProxyFromEnvironment
+)
+
+func mapAddress(ctx context.Context, address string) (string, error) {
+	req := &http.Request{
+		URL: &url.URL{
+			Scheme: "https",
+			Host:   address,
+		},
+	}
+	url, err := httpProxyFromEnvironment(req)
+	if err != nil {
+		return "", err
+	}
+	if url == nil {
+		return "", errDisabled
+	}
+	return url.Host, nil
+}
+
+// To read a response from a net.Conn, http.ReadResponse() takes a bufio.Reader.
+// It's possible that this reader reads more than what's need for the response and stores
+// those bytes in the buffer.
+// bufConn wraps the original net.Conn and the bufio.Reader to make sure we don't lose the
+// bytes in the buffer.
+type bufConn struct {
+	net.Conn
+	r io.Reader
+}
+
+func (c *bufConn) Read(b []byte) (int, error) {
+	return c.r.Read(b)
+}
+
+func doHTTPConnectHandshake(ctx context.Context, conn net.Conn, addr string) (_ net.Conn, err error) {
+	defer func() {
+		if err != nil {
+			conn.Close()
+		}
+	}()
+
+	req := (&http.Request{
+		Method: http.MethodConnect,
+		URL:    &url.URL{Host: addr},
+		Header: map[string][]string{"User-Agent": {grpcUA}},
+	})
+
+	if err := sendHTTPRequest(ctx, req, conn); err != nil {
+		return nil, fmt.Errorf("failed to write the HTTP request: %v", err)
+	}
+
+	r := bufio.NewReader(conn)
+	resp, err := http.ReadResponse(r, req)
+	if err != nil {
+		return nil, fmt.Errorf("reading server HTTP response: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		dump, err := httputil.DumpResponse(resp, true)
+		if err != nil {
+			return nil, fmt.Errorf("failed to do connect handshake, status code: %s", resp.Status)
+		}
+		return nil, fmt.Errorf("failed to do connect handshake, response: %q", dump)
+	}
+
+	return &bufConn{Conn: conn, r: r}, nil
+}
+
+// newProxyDialer returns a dialer that connects to proxy first if necessary.
+// The returned dialer checks if a proxy is necessary, dial to the proxy with the
+// provided dialer, does HTTP CONNECT handshake and returns the connection.
+func newProxyDialer(dialer func(context.Context, string) (net.Conn, error)) func(context.Context, string) (net.Conn, error) {
+	return func(ctx context.Context, addr string) (conn net.Conn, err error) {
+		var skipHandshake bool
+		newAddr, err := mapAddress(ctx, addr)
+		if err != nil {
+			if err != errDisabled {
+				return nil, err
+			}
+			skipHandshake = true
+			newAddr = addr
+		}
+
+		conn, err = dialer(ctx, newAddr)
+		if err != nil {
+			return
+		}
+		if !skipHandshake {
+			conn, err = doHTTPConnectHandshake(ctx, conn, addr)
+		}
+		return
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/reflection/README.md b/go/vendor/google.golang.org/grpc/reflection/README.md
new file mode 100644
index 0000000..04b6371
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/reflection/README.md
@@ -0,0 +1,18 @@
+# Reflection
+
+Package reflection implements server reflection service.
+
+The service implemented is defined in: https://github.com/grpc/grpc/blob/master/src/proto/grpc/reflection/v1alpha/reflection.proto.
+
+To register server reflection on a gRPC server:
+```go
+import "google.golang.org/grpc/reflection"
+
+s := grpc.NewServer()
+pb.RegisterYourOwnServer(s, &server{})
+
+// Register reflection service on gRPC server.
+reflection.Register(s)
+
+s.Serve(lis)
+```
diff --git a/go/vendor/google.golang.org/grpc/reflection/grpc_reflection_v1alpha/reflection.pb.go b/go/vendor/google.golang.org/grpc/reflection/grpc_reflection_v1alpha/reflection.pb.go
new file mode 100644
index 0000000..ae5aa7d
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/reflection/grpc_reflection_v1alpha/reflection.pb.go
@@ -0,0 +1,939 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: grpc_reflection_v1alpha/reflection.proto
+
+package grpc_reflection_v1alpha
+
+import proto "github.com/golang/protobuf/proto"
+import fmt "fmt"
+import math "math"
+
+import (
+	context "golang.org/x/net/context"
+	grpc "google.golang.org/grpc"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+// The message sent by the client when calling ServerReflectionInfo method.
+type ServerReflectionRequest struct {
+	Host string `protobuf:"bytes,1,opt,name=host,proto3" json:"host,omitempty"`
+	// To use reflection service, the client should set one of the following
+	// fields in message_request. The server distinguishes requests by their
+	// defined field and then handles them using corresponding methods.
+	//
+	// Types that are valid to be assigned to MessageRequest:
+	//	*ServerReflectionRequest_FileByFilename
+	//	*ServerReflectionRequest_FileContainingSymbol
+	//	*ServerReflectionRequest_FileContainingExtension
+	//	*ServerReflectionRequest_AllExtensionNumbersOfType
+	//	*ServerReflectionRequest_ListServices
+	MessageRequest       isServerReflectionRequest_MessageRequest `protobuf_oneof:"message_request"`
+	XXX_NoUnkeyedLiteral struct{}                                 `json:"-"`
+	XXX_unrecognized     []byte                                   `json:"-"`
+	XXX_sizecache        int32                                    `json:"-"`
+}
+
+func (m *ServerReflectionRequest) Reset()         { *m = ServerReflectionRequest{} }
+func (m *ServerReflectionRequest) String() string { return proto.CompactTextString(m) }
+func (*ServerReflectionRequest) ProtoMessage()    {}
+func (*ServerReflectionRequest) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{0}
+}
+func (m *ServerReflectionRequest) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ServerReflectionRequest.Unmarshal(m, b)
+}
+func (m *ServerReflectionRequest) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ServerReflectionRequest.Marshal(b, m, deterministic)
+}
+func (dst *ServerReflectionRequest) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ServerReflectionRequest.Merge(dst, src)
+}
+func (m *ServerReflectionRequest) XXX_Size() int {
+	return xxx_messageInfo_ServerReflectionRequest.Size(m)
+}
+func (m *ServerReflectionRequest) XXX_DiscardUnknown() {
+	xxx_messageInfo_ServerReflectionRequest.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ServerReflectionRequest proto.InternalMessageInfo
+
+func (m *ServerReflectionRequest) GetHost() string {
+	if m != nil {
+		return m.Host
+	}
+	return ""
+}
+
+type isServerReflectionRequest_MessageRequest interface {
+	isServerReflectionRequest_MessageRequest()
+}
+
+type ServerReflectionRequest_FileByFilename struct {
+	FileByFilename string `protobuf:"bytes,3,opt,name=file_by_filename,json=fileByFilename,proto3,oneof"`
+}
+
+type ServerReflectionRequest_FileContainingSymbol struct {
+	FileContainingSymbol string `protobuf:"bytes,4,opt,name=file_containing_symbol,json=fileContainingSymbol,proto3,oneof"`
+}
+
+type ServerReflectionRequest_FileContainingExtension struct {
+	FileContainingExtension *ExtensionRequest `protobuf:"bytes,5,opt,name=file_containing_extension,json=fileContainingExtension,proto3,oneof"`
+}
+
+type ServerReflectionRequest_AllExtensionNumbersOfType struct {
+	AllExtensionNumbersOfType string `protobuf:"bytes,6,opt,name=all_extension_numbers_of_type,json=allExtensionNumbersOfType,proto3,oneof"`
+}
+
+type ServerReflectionRequest_ListServices struct {
+	ListServices string `protobuf:"bytes,7,opt,name=list_services,json=listServices,proto3,oneof"`
+}
+
+func (*ServerReflectionRequest_FileByFilename) isServerReflectionRequest_MessageRequest() {}
+
+func (*ServerReflectionRequest_FileContainingSymbol) isServerReflectionRequest_MessageRequest() {}
+
+func (*ServerReflectionRequest_FileContainingExtension) isServerReflectionRequest_MessageRequest() {}
+
+func (*ServerReflectionRequest_AllExtensionNumbersOfType) isServerReflectionRequest_MessageRequest() {}
+
+func (*ServerReflectionRequest_ListServices) isServerReflectionRequest_MessageRequest() {}
+
+func (m *ServerReflectionRequest) GetMessageRequest() isServerReflectionRequest_MessageRequest {
+	if m != nil {
+		return m.MessageRequest
+	}
+	return nil
+}
+
+func (m *ServerReflectionRequest) GetFileByFilename() string {
+	if x, ok := m.GetMessageRequest().(*ServerReflectionRequest_FileByFilename); ok {
+		return x.FileByFilename
+	}
+	return ""
+}
+
+func (m *ServerReflectionRequest) GetFileContainingSymbol() string {
+	if x, ok := m.GetMessageRequest().(*ServerReflectionRequest_FileContainingSymbol); ok {
+		return x.FileContainingSymbol
+	}
+	return ""
+}
+
+func (m *ServerReflectionRequest) GetFileContainingExtension() *ExtensionRequest {
+	if x, ok := m.GetMessageRequest().(*ServerReflectionRequest_FileContainingExtension); ok {
+		return x.FileContainingExtension
+	}
+	return nil
+}
+
+func (m *ServerReflectionRequest) GetAllExtensionNumbersOfType() string {
+	if x, ok := m.GetMessageRequest().(*ServerReflectionRequest_AllExtensionNumbersOfType); ok {
+		return x.AllExtensionNumbersOfType
+	}
+	return ""
+}
+
+func (m *ServerReflectionRequest) GetListServices() string {
+	if x, ok := m.GetMessageRequest().(*ServerReflectionRequest_ListServices); ok {
+		return x.ListServices
+	}
+	return ""
+}
+
+// XXX_OneofFuncs is for the internal use of the proto package.
+func (*ServerReflectionRequest) XXX_OneofFuncs() (func(msg proto.Message, b *proto.Buffer) error, func(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error), func(msg proto.Message) (n int), []interface{}) {
+	return _ServerReflectionRequest_OneofMarshaler, _ServerReflectionRequest_OneofUnmarshaler, _ServerReflectionRequest_OneofSizer, []interface{}{
+		(*ServerReflectionRequest_FileByFilename)(nil),
+		(*ServerReflectionRequest_FileContainingSymbol)(nil),
+		(*ServerReflectionRequest_FileContainingExtension)(nil),
+		(*ServerReflectionRequest_AllExtensionNumbersOfType)(nil),
+		(*ServerReflectionRequest_ListServices)(nil),
+	}
+}
+
+func _ServerReflectionRequest_OneofMarshaler(msg proto.Message, b *proto.Buffer) error {
+	m := msg.(*ServerReflectionRequest)
+	// message_request
+	switch x := m.MessageRequest.(type) {
+	case *ServerReflectionRequest_FileByFilename:
+		b.EncodeVarint(3<<3 | proto.WireBytes)
+		b.EncodeStringBytes(x.FileByFilename)
+	case *ServerReflectionRequest_FileContainingSymbol:
+		b.EncodeVarint(4<<3 | proto.WireBytes)
+		b.EncodeStringBytes(x.FileContainingSymbol)
+	case *ServerReflectionRequest_FileContainingExtension:
+		b.EncodeVarint(5<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.FileContainingExtension); err != nil {
+			return err
+		}
+	case *ServerReflectionRequest_AllExtensionNumbersOfType:
+		b.EncodeVarint(6<<3 | proto.WireBytes)
+		b.EncodeStringBytes(x.AllExtensionNumbersOfType)
+	case *ServerReflectionRequest_ListServices:
+		b.EncodeVarint(7<<3 | proto.WireBytes)
+		b.EncodeStringBytes(x.ListServices)
+	case nil:
+	default:
+		return fmt.Errorf("ServerReflectionRequest.MessageRequest has unexpected type %T", x)
+	}
+	return nil
+}
+
+func _ServerReflectionRequest_OneofUnmarshaler(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error) {
+	m := msg.(*ServerReflectionRequest)
+	switch tag {
+	case 3: // message_request.file_by_filename
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		x, err := b.DecodeStringBytes()
+		m.MessageRequest = &ServerReflectionRequest_FileByFilename{x}
+		return true, err
+	case 4: // message_request.file_containing_symbol
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		x, err := b.DecodeStringBytes()
+		m.MessageRequest = &ServerReflectionRequest_FileContainingSymbol{x}
+		return true, err
+	case 5: // message_request.file_containing_extension
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(ExtensionRequest)
+		err := b.DecodeMessage(msg)
+		m.MessageRequest = &ServerReflectionRequest_FileContainingExtension{msg}
+		return true, err
+	case 6: // message_request.all_extension_numbers_of_type
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		x, err := b.DecodeStringBytes()
+		m.MessageRequest = &ServerReflectionRequest_AllExtensionNumbersOfType{x}
+		return true, err
+	case 7: // message_request.list_services
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		x, err := b.DecodeStringBytes()
+		m.MessageRequest = &ServerReflectionRequest_ListServices{x}
+		return true, err
+	default:
+		return false, nil
+	}
+}
+
+func _ServerReflectionRequest_OneofSizer(msg proto.Message) (n int) {
+	m := msg.(*ServerReflectionRequest)
+	// message_request
+	switch x := m.MessageRequest.(type) {
+	case *ServerReflectionRequest_FileByFilename:
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(len(x.FileByFilename)))
+		n += len(x.FileByFilename)
+	case *ServerReflectionRequest_FileContainingSymbol:
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(len(x.FileContainingSymbol)))
+		n += len(x.FileContainingSymbol)
+	case *ServerReflectionRequest_FileContainingExtension:
+		s := proto.Size(x.FileContainingExtension)
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case *ServerReflectionRequest_AllExtensionNumbersOfType:
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(len(x.AllExtensionNumbersOfType)))
+		n += len(x.AllExtensionNumbersOfType)
+	case *ServerReflectionRequest_ListServices:
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(len(x.ListServices)))
+		n += len(x.ListServices)
+	case nil:
+	default:
+		panic(fmt.Sprintf("proto: unexpected type %T in oneof", x))
+	}
+	return n
+}
+
+// The type name and extension number sent by the client when requesting
+// file_containing_extension.
+type ExtensionRequest struct {
+	// Fully-qualified type name. The format should be <package>.<type>
+	ContainingType       string   `protobuf:"bytes,1,opt,name=containing_type,json=containingType,proto3" json:"containing_type,omitempty"`
+	ExtensionNumber      int32    `protobuf:"varint,2,opt,name=extension_number,json=extensionNumber,proto3" json:"extension_number,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ExtensionRequest) Reset()         { *m = ExtensionRequest{} }
+func (m *ExtensionRequest) String() string { return proto.CompactTextString(m) }
+func (*ExtensionRequest) ProtoMessage()    {}
+func (*ExtensionRequest) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{1}
+}
+func (m *ExtensionRequest) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ExtensionRequest.Unmarshal(m, b)
+}
+func (m *ExtensionRequest) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ExtensionRequest.Marshal(b, m, deterministic)
+}
+func (dst *ExtensionRequest) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ExtensionRequest.Merge(dst, src)
+}
+func (m *ExtensionRequest) XXX_Size() int {
+	return xxx_messageInfo_ExtensionRequest.Size(m)
+}
+func (m *ExtensionRequest) XXX_DiscardUnknown() {
+	xxx_messageInfo_ExtensionRequest.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ExtensionRequest proto.InternalMessageInfo
+
+func (m *ExtensionRequest) GetContainingType() string {
+	if m != nil {
+		return m.ContainingType
+	}
+	return ""
+}
+
+func (m *ExtensionRequest) GetExtensionNumber() int32 {
+	if m != nil {
+		return m.ExtensionNumber
+	}
+	return 0
+}
+
+// The message sent by the server to answer ServerReflectionInfo method.
+type ServerReflectionResponse struct {
+	ValidHost       string                   `protobuf:"bytes,1,opt,name=valid_host,json=validHost,proto3" json:"valid_host,omitempty"`
+	OriginalRequest *ServerReflectionRequest `protobuf:"bytes,2,opt,name=original_request,json=originalRequest,proto3" json:"original_request,omitempty"`
+	// The server sets one of the following fields according to the
+	// message_request in the request.
+	//
+	// Types that are valid to be assigned to MessageResponse:
+	//	*ServerReflectionResponse_FileDescriptorResponse
+	//	*ServerReflectionResponse_AllExtensionNumbersResponse
+	//	*ServerReflectionResponse_ListServicesResponse
+	//	*ServerReflectionResponse_ErrorResponse
+	MessageResponse      isServerReflectionResponse_MessageResponse `protobuf_oneof:"message_response"`
+	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
+	XXX_unrecognized     []byte                                     `json:"-"`
+	XXX_sizecache        int32                                      `json:"-"`
+}
+
+func (m *ServerReflectionResponse) Reset()         { *m = ServerReflectionResponse{} }
+func (m *ServerReflectionResponse) String() string { return proto.CompactTextString(m) }
+func (*ServerReflectionResponse) ProtoMessage()    {}
+func (*ServerReflectionResponse) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{2}
+}
+func (m *ServerReflectionResponse) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ServerReflectionResponse.Unmarshal(m, b)
+}
+func (m *ServerReflectionResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ServerReflectionResponse.Marshal(b, m, deterministic)
+}
+func (dst *ServerReflectionResponse) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ServerReflectionResponse.Merge(dst, src)
+}
+func (m *ServerReflectionResponse) XXX_Size() int {
+	return xxx_messageInfo_ServerReflectionResponse.Size(m)
+}
+func (m *ServerReflectionResponse) XXX_DiscardUnknown() {
+	xxx_messageInfo_ServerReflectionResponse.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ServerReflectionResponse proto.InternalMessageInfo
+
+func (m *ServerReflectionResponse) GetValidHost() string {
+	if m != nil {
+		return m.ValidHost
+	}
+	return ""
+}
+
+func (m *ServerReflectionResponse) GetOriginalRequest() *ServerReflectionRequest {
+	if m != nil {
+		return m.OriginalRequest
+	}
+	return nil
+}
+
+type isServerReflectionResponse_MessageResponse interface {
+	isServerReflectionResponse_MessageResponse()
+}
+
+type ServerReflectionResponse_FileDescriptorResponse struct {
+	FileDescriptorResponse *FileDescriptorResponse `protobuf:"bytes,4,opt,name=file_descriptor_response,json=fileDescriptorResponse,proto3,oneof"`
+}
+
+type ServerReflectionResponse_AllExtensionNumbersResponse struct {
+	AllExtensionNumbersResponse *ExtensionNumberResponse `protobuf:"bytes,5,opt,name=all_extension_numbers_response,json=allExtensionNumbersResponse,proto3,oneof"`
+}
+
+type ServerReflectionResponse_ListServicesResponse struct {
+	ListServicesResponse *ListServiceResponse `protobuf:"bytes,6,opt,name=list_services_response,json=listServicesResponse,proto3,oneof"`
+}
+
+type ServerReflectionResponse_ErrorResponse struct {
+	ErrorResponse *ErrorResponse `protobuf:"bytes,7,opt,name=error_response,json=errorResponse,proto3,oneof"`
+}
+
+func (*ServerReflectionResponse_FileDescriptorResponse) isServerReflectionResponse_MessageResponse() {}
+
+func (*ServerReflectionResponse_AllExtensionNumbersResponse) isServerReflectionResponse_MessageResponse() {
+}
+
+func (*ServerReflectionResponse_ListServicesResponse) isServerReflectionResponse_MessageResponse() {}
+
+func (*ServerReflectionResponse_ErrorResponse) isServerReflectionResponse_MessageResponse() {}
+
+func (m *ServerReflectionResponse) GetMessageResponse() isServerReflectionResponse_MessageResponse {
+	if m != nil {
+		return m.MessageResponse
+	}
+	return nil
+}
+
+func (m *ServerReflectionResponse) GetFileDescriptorResponse() *FileDescriptorResponse {
+	if x, ok := m.GetMessageResponse().(*ServerReflectionResponse_FileDescriptorResponse); ok {
+		return x.FileDescriptorResponse
+	}
+	return nil
+}
+
+func (m *ServerReflectionResponse) GetAllExtensionNumbersResponse() *ExtensionNumberResponse {
+	if x, ok := m.GetMessageResponse().(*ServerReflectionResponse_AllExtensionNumbersResponse); ok {
+		return x.AllExtensionNumbersResponse
+	}
+	return nil
+}
+
+func (m *ServerReflectionResponse) GetListServicesResponse() *ListServiceResponse {
+	if x, ok := m.GetMessageResponse().(*ServerReflectionResponse_ListServicesResponse); ok {
+		return x.ListServicesResponse
+	}
+	return nil
+}
+
+func (m *ServerReflectionResponse) GetErrorResponse() *ErrorResponse {
+	if x, ok := m.GetMessageResponse().(*ServerReflectionResponse_ErrorResponse); ok {
+		return x.ErrorResponse
+	}
+	return nil
+}
+
+// XXX_OneofFuncs is for the internal use of the proto package.
+func (*ServerReflectionResponse) XXX_OneofFuncs() (func(msg proto.Message, b *proto.Buffer) error, func(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error), func(msg proto.Message) (n int), []interface{}) {
+	return _ServerReflectionResponse_OneofMarshaler, _ServerReflectionResponse_OneofUnmarshaler, _ServerReflectionResponse_OneofSizer, []interface{}{
+		(*ServerReflectionResponse_FileDescriptorResponse)(nil),
+		(*ServerReflectionResponse_AllExtensionNumbersResponse)(nil),
+		(*ServerReflectionResponse_ListServicesResponse)(nil),
+		(*ServerReflectionResponse_ErrorResponse)(nil),
+	}
+}
+
+func _ServerReflectionResponse_OneofMarshaler(msg proto.Message, b *proto.Buffer) error {
+	m := msg.(*ServerReflectionResponse)
+	// message_response
+	switch x := m.MessageResponse.(type) {
+	case *ServerReflectionResponse_FileDescriptorResponse:
+		b.EncodeVarint(4<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.FileDescriptorResponse); err != nil {
+			return err
+		}
+	case *ServerReflectionResponse_AllExtensionNumbersResponse:
+		b.EncodeVarint(5<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.AllExtensionNumbersResponse); err != nil {
+			return err
+		}
+	case *ServerReflectionResponse_ListServicesResponse:
+		b.EncodeVarint(6<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.ListServicesResponse); err != nil {
+			return err
+		}
+	case *ServerReflectionResponse_ErrorResponse:
+		b.EncodeVarint(7<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.ErrorResponse); err != nil {
+			return err
+		}
+	case nil:
+	default:
+		return fmt.Errorf("ServerReflectionResponse.MessageResponse has unexpected type %T", x)
+	}
+	return nil
+}
+
+func _ServerReflectionResponse_OneofUnmarshaler(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error) {
+	m := msg.(*ServerReflectionResponse)
+	switch tag {
+	case 4: // message_response.file_descriptor_response
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(FileDescriptorResponse)
+		err := b.DecodeMessage(msg)
+		m.MessageResponse = &ServerReflectionResponse_FileDescriptorResponse{msg}
+		return true, err
+	case 5: // message_response.all_extension_numbers_response
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(ExtensionNumberResponse)
+		err := b.DecodeMessage(msg)
+		m.MessageResponse = &ServerReflectionResponse_AllExtensionNumbersResponse{msg}
+		return true, err
+	case 6: // message_response.list_services_response
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(ListServiceResponse)
+		err := b.DecodeMessage(msg)
+		m.MessageResponse = &ServerReflectionResponse_ListServicesResponse{msg}
+		return true, err
+	case 7: // message_response.error_response
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(ErrorResponse)
+		err := b.DecodeMessage(msg)
+		m.MessageResponse = &ServerReflectionResponse_ErrorResponse{msg}
+		return true, err
+	default:
+		return false, nil
+	}
+}
+
+func _ServerReflectionResponse_OneofSizer(msg proto.Message) (n int) {
+	m := msg.(*ServerReflectionResponse)
+	// message_response
+	switch x := m.MessageResponse.(type) {
+	case *ServerReflectionResponse_FileDescriptorResponse:
+		s := proto.Size(x.FileDescriptorResponse)
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case *ServerReflectionResponse_AllExtensionNumbersResponse:
+		s := proto.Size(x.AllExtensionNumbersResponse)
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case *ServerReflectionResponse_ListServicesResponse:
+		s := proto.Size(x.ListServicesResponse)
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case *ServerReflectionResponse_ErrorResponse:
+		s := proto.Size(x.ErrorResponse)
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case nil:
+	default:
+		panic(fmt.Sprintf("proto: unexpected type %T in oneof", x))
+	}
+	return n
+}
+
+// Serialized FileDescriptorProto messages sent by the server answering
+// a file_by_filename, file_containing_symbol, or file_containing_extension
+// request.
+type FileDescriptorResponse struct {
+	// Serialized FileDescriptorProto messages. We avoid taking a dependency on
+	// descriptor.proto, which uses proto2 only features, by making them opaque
+	// bytes instead.
+	FileDescriptorProto  [][]byte `protobuf:"bytes,1,rep,name=file_descriptor_proto,json=fileDescriptorProto,proto3" json:"file_descriptor_proto,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *FileDescriptorResponse) Reset()         { *m = FileDescriptorResponse{} }
+func (m *FileDescriptorResponse) String() string { return proto.CompactTextString(m) }
+func (*FileDescriptorResponse) ProtoMessage()    {}
+func (*FileDescriptorResponse) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{3}
+}
+func (m *FileDescriptorResponse) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_FileDescriptorResponse.Unmarshal(m, b)
+}
+func (m *FileDescriptorResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_FileDescriptorResponse.Marshal(b, m, deterministic)
+}
+func (dst *FileDescriptorResponse) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_FileDescriptorResponse.Merge(dst, src)
+}
+func (m *FileDescriptorResponse) XXX_Size() int {
+	return xxx_messageInfo_FileDescriptorResponse.Size(m)
+}
+func (m *FileDescriptorResponse) XXX_DiscardUnknown() {
+	xxx_messageInfo_FileDescriptorResponse.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_FileDescriptorResponse proto.InternalMessageInfo
+
+func (m *FileDescriptorResponse) GetFileDescriptorProto() [][]byte {
+	if m != nil {
+		return m.FileDescriptorProto
+	}
+	return nil
+}
+
+// A list of extension numbers sent by the server answering
+// all_extension_numbers_of_type request.
+type ExtensionNumberResponse struct {
+	// Full name of the base type, including the package name. The format
+	// is <package>.<type>
+	BaseTypeName         string   `protobuf:"bytes,1,opt,name=base_type_name,json=baseTypeName,proto3" json:"base_type_name,omitempty"`
+	ExtensionNumber      []int32  `protobuf:"varint,2,rep,packed,name=extension_number,json=extensionNumber,proto3" json:"extension_number,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ExtensionNumberResponse) Reset()         { *m = ExtensionNumberResponse{} }
+func (m *ExtensionNumberResponse) String() string { return proto.CompactTextString(m) }
+func (*ExtensionNumberResponse) ProtoMessage()    {}
+func (*ExtensionNumberResponse) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{4}
+}
+func (m *ExtensionNumberResponse) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ExtensionNumberResponse.Unmarshal(m, b)
+}
+func (m *ExtensionNumberResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ExtensionNumberResponse.Marshal(b, m, deterministic)
+}
+func (dst *ExtensionNumberResponse) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ExtensionNumberResponse.Merge(dst, src)
+}
+func (m *ExtensionNumberResponse) XXX_Size() int {
+	return xxx_messageInfo_ExtensionNumberResponse.Size(m)
+}
+func (m *ExtensionNumberResponse) XXX_DiscardUnknown() {
+	xxx_messageInfo_ExtensionNumberResponse.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ExtensionNumberResponse proto.InternalMessageInfo
+
+func (m *ExtensionNumberResponse) GetBaseTypeName() string {
+	if m != nil {
+		return m.BaseTypeName
+	}
+	return ""
+}
+
+func (m *ExtensionNumberResponse) GetExtensionNumber() []int32 {
+	if m != nil {
+		return m.ExtensionNumber
+	}
+	return nil
+}
+
+// A list of ServiceResponse sent by the server answering list_services request.
+type ListServiceResponse struct {
+	// The information of each service may be expanded in the future, so we use
+	// ServiceResponse message to encapsulate it.
+	Service              []*ServiceResponse `protobuf:"bytes,1,rep,name=service,proto3" json:"service,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}           `json:"-"`
+	XXX_unrecognized     []byte             `json:"-"`
+	XXX_sizecache        int32              `json:"-"`
+}
+
+func (m *ListServiceResponse) Reset()         { *m = ListServiceResponse{} }
+func (m *ListServiceResponse) String() string { return proto.CompactTextString(m) }
+func (*ListServiceResponse) ProtoMessage()    {}
+func (*ListServiceResponse) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{5}
+}
+func (m *ListServiceResponse) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ListServiceResponse.Unmarshal(m, b)
+}
+func (m *ListServiceResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ListServiceResponse.Marshal(b, m, deterministic)
+}
+func (dst *ListServiceResponse) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ListServiceResponse.Merge(dst, src)
+}
+func (m *ListServiceResponse) XXX_Size() int {
+	return xxx_messageInfo_ListServiceResponse.Size(m)
+}
+func (m *ListServiceResponse) XXX_DiscardUnknown() {
+	xxx_messageInfo_ListServiceResponse.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ListServiceResponse proto.InternalMessageInfo
+
+func (m *ListServiceResponse) GetService() []*ServiceResponse {
+	if m != nil {
+		return m.Service
+	}
+	return nil
+}
+
+// The information of a single service used by ListServiceResponse to answer
+// list_services request.
+type ServiceResponse struct {
+	// Full name of a registered service, including its package name. The format
+	// is <package>.<service>
+	Name                 string   `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ServiceResponse) Reset()         { *m = ServiceResponse{} }
+func (m *ServiceResponse) String() string { return proto.CompactTextString(m) }
+func (*ServiceResponse) ProtoMessage()    {}
+func (*ServiceResponse) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{6}
+}
+func (m *ServiceResponse) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ServiceResponse.Unmarshal(m, b)
+}
+func (m *ServiceResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ServiceResponse.Marshal(b, m, deterministic)
+}
+func (dst *ServiceResponse) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ServiceResponse.Merge(dst, src)
+}
+func (m *ServiceResponse) XXX_Size() int {
+	return xxx_messageInfo_ServiceResponse.Size(m)
+}
+func (m *ServiceResponse) XXX_DiscardUnknown() {
+	xxx_messageInfo_ServiceResponse.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ServiceResponse proto.InternalMessageInfo
+
+func (m *ServiceResponse) GetName() string {
+	if m != nil {
+		return m.Name
+	}
+	return ""
+}
+
+// The error code and error message sent by the server when an error occurs.
+type ErrorResponse struct {
+	// This field uses the error codes defined in grpc::StatusCode.
+	ErrorCode            int32    `protobuf:"varint,1,opt,name=error_code,json=errorCode,proto3" json:"error_code,omitempty"`
+	ErrorMessage         string   `protobuf:"bytes,2,opt,name=error_message,json=errorMessage,proto3" json:"error_message,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *ErrorResponse) Reset()         { *m = ErrorResponse{} }
+func (m *ErrorResponse) String() string { return proto.CompactTextString(m) }
+func (*ErrorResponse) ProtoMessage()    {}
+func (*ErrorResponse) Descriptor() ([]byte, []int) {
+	return fileDescriptor_reflection_178bd1e101bf8b63, []int{7}
+}
+func (m *ErrorResponse) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_ErrorResponse.Unmarshal(m, b)
+}
+func (m *ErrorResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_ErrorResponse.Marshal(b, m, deterministic)
+}
+func (dst *ErrorResponse) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_ErrorResponse.Merge(dst, src)
+}
+func (m *ErrorResponse) XXX_Size() int {
+	return xxx_messageInfo_ErrorResponse.Size(m)
+}
+func (m *ErrorResponse) XXX_DiscardUnknown() {
+	xxx_messageInfo_ErrorResponse.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_ErrorResponse proto.InternalMessageInfo
+
+func (m *ErrorResponse) GetErrorCode() int32 {
+	if m != nil {
+		return m.ErrorCode
+	}
+	return 0
+}
+
+func (m *ErrorResponse) GetErrorMessage() string {
+	if m != nil {
+		return m.ErrorMessage
+	}
+	return ""
+}
+
+func init() {
+	proto.RegisterType((*ServerReflectionRequest)(nil), "grpc.reflection.v1alpha.ServerReflectionRequest")
+	proto.RegisterType((*ExtensionRequest)(nil), "grpc.reflection.v1alpha.ExtensionRequest")
+	proto.RegisterType((*ServerReflectionResponse)(nil), "grpc.reflection.v1alpha.ServerReflectionResponse")
+	proto.RegisterType((*FileDescriptorResponse)(nil), "grpc.reflection.v1alpha.FileDescriptorResponse")
+	proto.RegisterType((*ExtensionNumberResponse)(nil), "grpc.reflection.v1alpha.ExtensionNumberResponse")
+	proto.RegisterType((*ListServiceResponse)(nil), "grpc.reflection.v1alpha.ListServiceResponse")
+	proto.RegisterType((*ServiceResponse)(nil), "grpc.reflection.v1alpha.ServiceResponse")
+	proto.RegisterType((*ErrorResponse)(nil), "grpc.reflection.v1alpha.ErrorResponse")
+}
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ context.Context
+var _ grpc.ClientConn
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+const _ = grpc.SupportPackageIsVersion4
+
+// ServerReflectionClient is the client API for ServerReflection service.
+//
+// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.
+type ServerReflectionClient interface {
+	// The reflection service is structured as a bidirectional stream, ensuring
+	// all related requests go to a single server.
+	ServerReflectionInfo(ctx context.Context, opts ...grpc.CallOption) (ServerReflection_ServerReflectionInfoClient, error)
+}
+
+type serverReflectionClient struct {
+	cc *grpc.ClientConn
+}
+
+func NewServerReflectionClient(cc *grpc.ClientConn) ServerReflectionClient {
+	return &serverReflectionClient{cc}
+}
+
+func (c *serverReflectionClient) ServerReflectionInfo(ctx context.Context, opts ...grpc.CallOption) (ServerReflection_ServerReflectionInfoClient, error) {
+	stream, err := c.cc.NewStream(ctx, &_ServerReflection_serviceDesc.Streams[0], "/grpc.reflection.v1alpha.ServerReflection/ServerReflectionInfo", opts...)
+	if err != nil {
+		return nil, err
+	}
+	x := &serverReflectionServerReflectionInfoClient{stream}
+	return x, nil
+}
+
+type ServerReflection_ServerReflectionInfoClient interface {
+	Send(*ServerReflectionRequest) error
+	Recv() (*ServerReflectionResponse, error)
+	grpc.ClientStream
+}
+
+type serverReflectionServerReflectionInfoClient struct {
+	grpc.ClientStream
+}
+
+func (x *serverReflectionServerReflectionInfoClient) Send(m *ServerReflectionRequest) error {
+	return x.ClientStream.SendMsg(m)
+}
+
+func (x *serverReflectionServerReflectionInfoClient) Recv() (*ServerReflectionResponse, error) {
+	m := new(ServerReflectionResponse)
+	if err := x.ClientStream.RecvMsg(m); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+// ServerReflectionServer is the server API for ServerReflection service.
+type ServerReflectionServer interface {
+	// The reflection service is structured as a bidirectional stream, ensuring
+	// all related requests go to a single server.
+	ServerReflectionInfo(ServerReflection_ServerReflectionInfoServer) error
+}
+
+func RegisterServerReflectionServer(s *grpc.Server, srv ServerReflectionServer) {
+	s.RegisterService(&_ServerReflection_serviceDesc, srv)
+}
+
+func _ServerReflection_ServerReflectionInfo_Handler(srv interface{}, stream grpc.ServerStream) error {
+	return srv.(ServerReflectionServer).ServerReflectionInfo(&serverReflectionServerReflectionInfoServer{stream})
+}
+
+type ServerReflection_ServerReflectionInfoServer interface {
+	Send(*ServerReflectionResponse) error
+	Recv() (*ServerReflectionRequest, error)
+	grpc.ServerStream
+}
+
+type serverReflectionServerReflectionInfoServer struct {
+	grpc.ServerStream
+}
+
+func (x *serverReflectionServerReflectionInfoServer) Send(m *ServerReflectionResponse) error {
+	return x.ServerStream.SendMsg(m)
+}
+
+func (x *serverReflectionServerReflectionInfoServer) Recv() (*ServerReflectionRequest, error) {
+	m := new(ServerReflectionRequest)
+	if err := x.ServerStream.RecvMsg(m); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+var _ServerReflection_serviceDesc = grpc.ServiceDesc{
+	ServiceName: "grpc.reflection.v1alpha.ServerReflection",
+	HandlerType: (*ServerReflectionServer)(nil),
+	Methods:     []grpc.MethodDesc{},
+	Streams: []grpc.StreamDesc{
+		{
+			StreamName:    "ServerReflectionInfo",
+			Handler:       _ServerReflection_ServerReflectionInfo_Handler,
+			ServerStreams: true,
+			ClientStreams: true,
+		},
+	},
+	Metadata: "grpc_reflection_v1alpha/reflection.proto",
+}
+
+func init() {
+	proto.RegisterFile("grpc_reflection_v1alpha/reflection.proto", fileDescriptor_reflection_178bd1e101bf8b63)
+}
+
+var fileDescriptor_reflection_178bd1e101bf8b63 = []byte{
+	// 656 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x94, 0x54, 0x51, 0x73, 0xd2, 0x40,
+	0x10, 0x6e, 0x5a, 0x68, 0x87, 0x85, 0x02, 0x5e, 0x2b, 0xa4, 0x3a, 0x75, 0x98, 0x68, 0x35, 0x75,
+	0x1c, 0xda, 0xe2, 0x8c, 0x3f, 0x80, 0xaa, 0x83, 0x33, 0xb5, 0x75, 0x0e, 0x5f, 0x1c, 0x1f, 0x6e,
+	0x02, 0x2c, 0x34, 0x1a, 0x72, 0xf1, 0x2e, 0x45, 0x79, 0xf2, 0x47, 0xf8, 0xa3, 0xfc, 0x4b, 0x3e,
+	0x3a, 0x77, 0x09, 0x21, 0xa4, 0x44, 0xa7, 0x4f, 0x30, 0xdf, 0xee, 0xde, 0xb7, 0xbb, 0xdf, 0xb7,
+	0x01, 0x7b, 0x22, 0x82, 0x21, 0x13, 0x38, 0xf6, 0x70, 0x18, 0xba, 0xdc, 0x67, 0xb3, 0x33, 0xc7,
+	0x0b, 0xae, 0x9d, 0x93, 0x25, 0xd4, 0x0e, 0x04, 0x0f, 0x39, 0x69, 0xaa, 0xcc, 0x76, 0x0a, 0x8e,
+	0x33, 0xad, 0x3f, 0x9b, 0xd0, 0xec, 0xa3, 0x98, 0xa1, 0xa0, 0x49, 0x90, 0xe2, 0xb7, 0x1b, 0x94,
+	0x21, 0x21, 0x50, 0xb8, 0xe6, 0x32, 0x34, 0x8d, 0x96, 0x61, 0x97, 0xa8, 0xfe, 0x4f, 0x9e, 0x43,
+	0x7d, 0xec, 0x7a, 0xc8, 0x06, 0x73, 0xa6, 0x7e, 0x7d, 0x67, 0x8a, 0xe6, 0x96, 0x8a, 0xf7, 0x36,
+	0x68, 0x55, 0x21, 0xdd, 0xf9, 0xdb, 0x18, 0x27, 0xaf, 0xa0, 0xa1, 0x73, 0x87, 0xdc, 0x0f, 0x1d,
+	0xd7, 0x77, 0xfd, 0x09, 0x93, 0xf3, 0xe9, 0x80, 0x7b, 0x66, 0x21, 0xae, 0xd8, 0x57, 0xf1, 0xf3,
+	0x24, 0xdc, 0xd7, 0x51, 0x32, 0x81, 0x83, 0x6c, 0x1d, 0xfe, 0x08, 0xd1, 0x97, 0x2e, 0xf7, 0xcd,
+	0x62, 0xcb, 0xb0, 0xcb, 0x9d, 0xe3, 0x76, 0xce, 0x40, 0xed, 0x37, 0x8b, 0xcc, 0x78, 0x8a, 0xde,
+	0x06, 0x6d, 0xae, 0xb2, 0x24, 0x19, 0xa4, 0x0b, 0x87, 0x8e, 0xe7, 0x2d, 0x1f, 0x67, 0xfe, 0xcd,
+	0x74, 0x80, 0x42, 0x32, 0x3e, 0x66, 0xe1, 0x3c, 0x40, 0x73, 0x3b, 0xee, 0xf3, 0xc0, 0xf1, 0xbc,
+	0xa4, 0xec, 0x32, 0x4a, 0xba, 0x1a, 0x7f, 0x9c, 0x07, 0x48, 0x8e, 0x60, 0xd7, 0x73, 0x65, 0xc8,
+	0x24, 0x8a, 0x99, 0x3b, 0x44, 0x69, 0xee, 0xc4, 0x35, 0x15, 0x05, 0xf7, 0x63, 0xb4, 0x7b, 0x0f,
+	0x6a, 0x53, 0x94, 0xd2, 0x99, 0x20, 0x13, 0x51, 0x63, 0xd6, 0x18, 0xea, 0xd9, 0x66, 0xc9, 0x33,
+	0xa8, 0xa5, 0xa6, 0xd6, 0x3d, 0x44, 0xdb, 0xaf, 0x2e, 0x61, 0x4d, 0x7b, 0x0c, 0xf5, 0x6c, 0xdb,
+	0xe6, 0x66, 0xcb, 0xb0, 0x8b, 0xb4, 0x86, 0xab, 0x8d, 0x5a, 0xbf, 0x0b, 0x60, 0xde, 0x96, 0x58,
+	0x06, 0xdc, 0x97, 0x48, 0x0e, 0x01, 0x66, 0x8e, 0xe7, 0x8e, 0x58, 0x4a, 0xe9, 0x92, 0x46, 0x7a,
+	0x4a, 0xee, 0xcf, 0x50, 0xe7, 0xc2, 0x9d, 0xb8, 0xbe, 0xe3, 0x2d, 0xfa, 0xd6, 0x34, 0xe5, 0xce,
+	0x69, 0xae, 0x02, 0x39, 0x76, 0xa2, 0xb5, 0xc5, 0x4b, 0x8b, 0x61, 0xbf, 0x82, 0xa9, 0x75, 0x1e,
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+	0x1e, 0xad, 0xd7, 0x3a, 0xa1, 0x2c, 0xfe, 0x67, 0xae, 0x8c, 0x01, 0x52, 0x9c, 0x0f, 0xd7, 0xd8,
+	0x23, 0x21, 0x1e, 0x41, 0x63, 0xc5, 0x20, 0x4b, 0xc2, 0x6d, 0x4d, 0xf8, 0x22, 0x97, 0xf0, 0x62,
+	0x69, 0xa0, 0x14, 0xd9, 0x7e, 0xda, 0x57, 0x09, 0xcb, 0x15, 0x54, 0x51, 0x88, 0xf4, 0x06, 0x77,
+	0xf4, 0xeb, 0x4f, 0xf3, 0xc7, 0x51, 0xe9, 0xa9, 0x77, 0x77, 0x31, 0x0d, 0x74, 0x09, 0xd4, 0x97,
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+	0xbb, 0xb2, 0x71, 0x75, 0x79, 0x91, 0x62, 0x43, 0x3e, 0x8a, 0x52, 0x8b, 0xb4, 0xa4, 0x91, 0x73,
+	0x3e, 0x42, 0xf2, 0x18, 0x22, 0x41, 0x58, 0xac, 0x82, 0x3e, 0xbb, 0x12, 0xad, 0x68, 0xf0, 0x7d,
+	0x84, 0x75, 0x7e, 0x19, 0x50, 0xcf, 0x9e, 0x1b, 0xf9, 0x09, 0xfb, 0x59, 0xec, 0x9d, 0x3f, 0xe6,
+	0xe4, 0xce, 0x17, 0xfb, 0xe0, 0xec, 0x0e, 0x15, 0xd1, 0x54, 0xb6, 0x71, 0x6a, 0x0c, 0xb6, 0xb5,
+	0xf4, 0x2f, 0xff, 0x06, 0x00, 0x00, 0xff, 0xff, 0x85, 0x02, 0x09, 0x9d, 0x9f, 0x06, 0x00, 0x00,
+}
diff --git a/go/vendor/google.golang.org/grpc/reflection/grpc_reflection_v1alpha/reflection.proto b/go/vendor/google.golang.org/grpc/reflection/grpc_reflection_v1alpha/reflection.proto
new file mode 100644
index 0000000..99b00df
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/reflection/grpc_reflection_v1alpha/reflection.proto
@@ -0,0 +1,136 @@
+// Copyright 2016 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Service exported by server reflection
+
+syntax = "proto3";
+
+package grpc.reflection.v1alpha;
+
+service ServerReflection {
+  // The reflection service is structured as a bidirectional stream, ensuring
+  // all related requests go to a single server.
+  rpc ServerReflectionInfo(stream ServerReflectionRequest)
+      returns (stream ServerReflectionResponse);
+}
+
+// The message sent by the client when calling ServerReflectionInfo method.
+message ServerReflectionRequest {
+  string host = 1;
+  // To use reflection service, the client should set one of the following
+  // fields in message_request. The server distinguishes requests by their
+  // defined field and then handles them using corresponding methods.
+  oneof message_request {
+    // Find a proto file by the file name.
+    string file_by_filename = 3;
+
+    // Find the proto file that declares the given fully-qualified symbol name.
+    // This field should be a fully-qualified symbol name
+    // (e.g. <package>.<service>[.<method>] or <package>.<type>).
+    string file_containing_symbol = 4;
+
+    // Find the proto file which defines an extension extending the given
+    // message type with the given field number.
+    ExtensionRequest file_containing_extension = 5;
+
+    // Finds the tag numbers used by all known extensions of extendee_type, and
+    // appends them to ExtensionNumberResponse in an undefined order.
+    // Its corresponding method is best-effort: it's not guaranteed that the
+    // reflection service will implement this method, and it's not guaranteed
+    // that this method will provide all extensions. Returns
+    // StatusCode::UNIMPLEMENTED if it's not implemented.
+    // This field should be a fully-qualified type name. The format is
+    // <package>.<type>
+    string all_extension_numbers_of_type = 6;
+
+    // List the full names of registered services. The content will not be
+    // checked.
+    string list_services = 7;
+  }
+}
+
+// The type name and extension number sent by the client when requesting
+// file_containing_extension.
+message ExtensionRequest {
+  // Fully-qualified type name. The format should be <package>.<type>
+  string containing_type = 1;
+  int32 extension_number = 2;
+}
+
+// The message sent by the server to answer ServerReflectionInfo method.
+message ServerReflectionResponse {
+  string valid_host = 1;
+  ServerReflectionRequest original_request = 2;
+  // The server sets one of the following fields according to the
+  // message_request in the request.
+  oneof message_response {
+    // This message is used to answer file_by_filename, file_containing_symbol,
+    // file_containing_extension requests with transitive dependencies.
+    // As the repeated label is not allowed in oneof fields, we use a
+    // FileDescriptorResponse message to encapsulate the repeated fields.
+    // The reflection service is allowed to avoid sending FileDescriptorProtos
+    // that were previously sent in response to earlier requests in the stream.
+    FileDescriptorResponse file_descriptor_response = 4;
+
+    // This message is used to answer all_extension_numbers_of_type requests.
+    ExtensionNumberResponse all_extension_numbers_response = 5;
+
+    // This message is used to answer list_services requests.
+    ListServiceResponse list_services_response = 6;
+
+    // This message is used when an error occurs.
+    ErrorResponse error_response = 7;
+  }
+}
+
+// Serialized FileDescriptorProto messages sent by the server answering
+// a file_by_filename, file_containing_symbol, or file_containing_extension
+// request.
+message FileDescriptorResponse {
+  // Serialized FileDescriptorProto messages. We avoid taking a dependency on
+  // descriptor.proto, which uses proto2 only features, by making them opaque
+  // bytes instead.
+  repeated bytes file_descriptor_proto = 1;
+}
+
+// A list of extension numbers sent by the server answering
+// all_extension_numbers_of_type request.
+message ExtensionNumberResponse {
+  // Full name of the base type, including the package name. The format
+  // is <package>.<type>
+  string base_type_name = 1;
+  repeated int32 extension_number = 2;
+}
+
+// A list of ServiceResponse sent by the server answering list_services request.
+message ListServiceResponse {
+  // The information of each service may be expanded in the future, so we use
+  // ServiceResponse message to encapsulate it.
+  repeated ServiceResponse service = 1;
+}
+
+// The information of a single service used by ListServiceResponse to answer
+// list_services request.
+message ServiceResponse {
+  // Full name of a registered service, including its package name. The format
+  // is <package>.<service>
+  string name = 1;
+}
+
+// The error code and error message sent by the server when an error occurs.
+message ErrorResponse {
+  // This field uses the error codes defined in grpc::StatusCode.
+  int32 error_code = 1;
+  string error_message = 2;
+}
diff --git a/go/vendor/google.golang.org/grpc/reflection/serverreflection.go b/go/vendor/google.golang.org/grpc/reflection/serverreflection.go
new file mode 100644
index 0000000..dd22a2d
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/reflection/serverreflection.go
@@ -0,0 +1,454 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+//go:generate protoc --go_out=plugins=grpc:. grpc_reflection_v1alpha/reflection.proto
+
+/*
+Package reflection implements server reflection service.
+
+The service implemented is defined in:
+https://github.com/grpc/grpc/blob/master/src/proto/grpc/reflection/v1alpha/reflection.proto.
+
+To register server reflection on a gRPC server:
+	import "google.golang.org/grpc/reflection"
+
+	s := grpc.NewServer()
+	pb.RegisterYourOwnServer(s, &server{})
+
+	// Register reflection service on gRPC server.
+	reflection.Register(s)
+
+	s.Serve(lis)
+
+*/
+package reflection // import "google.golang.org/grpc/reflection"
+
+import (
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"reflect"
+	"sort"
+	"sync"
+
+	"github.com/golang/protobuf/proto"
+	dpb "github.com/golang/protobuf/protoc-gen-go/descriptor"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	rpb "google.golang.org/grpc/reflection/grpc_reflection_v1alpha"
+	"google.golang.org/grpc/status"
+)
+
+type serverReflectionServer struct {
+	s *grpc.Server
+
+	initSymbols  sync.Once
+	serviceNames []string
+	symbols      map[string]*dpb.FileDescriptorProto // map of fully-qualified names to files
+}
+
+// Register registers the server reflection service on the given gRPC server.
+func Register(s *grpc.Server) {
+	rpb.RegisterServerReflectionServer(s, &serverReflectionServer{
+		s: s,
+	})
+}
+
+// protoMessage is used for type assertion on proto messages.
+// Generated proto message implements function Descriptor(), but Descriptor()
+// is not part of interface proto.Message. This interface is needed to
+// call Descriptor().
+type protoMessage interface {
+	Descriptor() ([]byte, []int)
+}
+
+func (s *serverReflectionServer) getSymbols() (svcNames []string, symbolIndex map[string]*dpb.FileDescriptorProto) {
+	s.initSymbols.Do(func() {
+		serviceInfo := s.s.GetServiceInfo()
+
+		s.symbols = map[string]*dpb.FileDescriptorProto{}
+		s.serviceNames = make([]string, 0, len(serviceInfo))
+		processed := map[string]struct{}{}
+		for svc, info := range serviceInfo {
+			s.serviceNames = append(s.serviceNames, svc)
+			fdenc, ok := parseMetadata(info.Metadata)
+			if !ok {
+				continue
+			}
+			fd, err := decodeFileDesc(fdenc)
+			if err != nil {
+				continue
+			}
+			s.processFile(fd, processed)
+		}
+		sort.Strings(s.serviceNames)
+	})
+
+	return s.serviceNames, s.symbols
+}
+
+func (s *serverReflectionServer) processFile(fd *dpb.FileDescriptorProto, processed map[string]struct{}) {
+	filename := fd.GetName()
+	if _, ok := processed[filename]; ok {
+		return
+	}
+	processed[filename] = struct{}{}
+
+	prefix := fd.GetPackage()
+
+	for _, msg := range fd.MessageType {
+		s.processMessage(fd, prefix, msg)
+	}
+	for _, en := range fd.EnumType {
+		s.processEnum(fd, prefix, en)
+	}
+	for _, ext := range fd.Extension {
+		s.processField(fd, prefix, ext)
+	}
+	for _, svc := range fd.Service {
+		svcName := fqn(prefix, svc.GetName())
+		s.symbols[svcName] = fd
+		for _, meth := range svc.Method {
+			name := fqn(svcName, meth.GetName())
+			s.symbols[name] = fd
+		}
+	}
+
+	for _, dep := range fd.Dependency {
+		fdenc := proto.FileDescriptor(dep)
+		fdDep, err := decodeFileDesc(fdenc)
+		if err != nil {
+			continue
+		}
+		s.processFile(fdDep, processed)
+	}
+}
+
+func (s *serverReflectionServer) processMessage(fd *dpb.FileDescriptorProto, prefix string, msg *dpb.DescriptorProto) {
+	msgName := fqn(prefix, msg.GetName())
+	s.symbols[msgName] = fd
+
+	for _, nested := range msg.NestedType {
+		s.processMessage(fd, msgName, nested)
+	}
+	for _, en := range msg.EnumType {
+		s.processEnum(fd, msgName, en)
+	}
+	for _, ext := range msg.Extension {
+		s.processField(fd, msgName, ext)
+	}
+	for _, fld := range msg.Field {
+		s.processField(fd, msgName, fld)
+	}
+	for _, oneof := range msg.OneofDecl {
+		oneofName := fqn(msgName, oneof.GetName())
+		s.symbols[oneofName] = fd
+	}
+}
+
+func (s *serverReflectionServer) processEnum(fd *dpb.FileDescriptorProto, prefix string, en *dpb.EnumDescriptorProto) {
+	enName := fqn(prefix, en.GetName())
+	s.symbols[enName] = fd
+
+	for _, val := range en.Value {
+		valName := fqn(enName, val.GetName())
+		s.symbols[valName] = fd
+	}
+}
+
+func (s *serverReflectionServer) processField(fd *dpb.FileDescriptorProto, prefix string, fld *dpb.FieldDescriptorProto) {
+	fldName := fqn(prefix, fld.GetName())
+	s.symbols[fldName] = fd
+}
+
+func fqn(prefix, name string) string {
+	if prefix == "" {
+		return name
+	}
+	return prefix + "." + name
+}
+
+// fileDescForType gets the file descriptor for the given type.
+// The given type should be a proto message.
+func (s *serverReflectionServer) fileDescForType(st reflect.Type) (*dpb.FileDescriptorProto, error) {
+	m, ok := reflect.Zero(reflect.PtrTo(st)).Interface().(protoMessage)
+	if !ok {
+		return nil, fmt.Errorf("failed to create message from type: %v", st)
+	}
+	enc, _ := m.Descriptor()
+
+	return decodeFileDesc(enc)
+}
+
+// decodeFileDesc does decompression and unmarshalling on the given
+// file descriptor byte slice.
+func decodeFileDesc(enc []byte) (*dpb.FileDescriptorProto, error) {
+	raw, err := decompress(enc)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decompress enc: %v", err)
+	}
+
+	fd := new(dpb.FileDescriptorProto)
+	if err := proto.Unmarshal(raw, fd); err != nil {
+		return nil, fmt.Errorf("bad descriptor: %v", err)
+	}
+	return fd, nil
+}
+
+// decompress does gzip decompression.
+func decompress(b []byte) ([]byte, error) {
+	r, err := gzip.NewReader(bytes.NewReader(b))
+	if err != nil {
+		return nil, fmt.Errorf("bad gzipped descriptor: %v", err)
+	}
+	out, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, fmt.Errorf("bad gzipped descriptor: %v", err)
+	}
+	return out, nil
+}
+
+func typeForName(name string) (reflect.Type, error) {
+	pt := proto.MessageType(name)
+	if pt == nil {
+		return nil, fmt.Errorf("unknown type: %q", name)
+	}
+	st := pt.Elem()
+
+	return st, nil
+}
+
+func fileDescContainingExtension(st reflect.Type, ext int32) (*dpb.FileDescriptorProto, error) {
+	m, ok := reflect.Zero(reflect.PtrTo(st)).Interface().(proto.Message)
+	if !ok {
+		return nil, fmt.Errorf("failed to create message from type: %v", st)
+	}
+
+	var extDesc *proto.ExtensionDesc
+	for id, desc := range proto.RegisteredExtensions(m) {
+		if id == ext {
+			extDesc = desc
+			break
+		}
+	}
+
+	if extDesc == nil {
+		return nil, fmt.Errorf("failed to find registered extension for extension number %v", ext)
+	}
+
+	return decodeFileDesc(proto.FileDescriptor(extDesc.Filename))
+}
+
+func (s *serverReflectionServer) allExtensionNumbersForType(st reflect.Type) ([]int32, error) {
+	m, ok := reflect.Zero(reflect.PtrTo(st)).Interface().(proto.Message)
+	if !ok {
+		return nil, fmt.Errorf("failed to create message from type: %v", st)
+	}
+
+	exts := proto.RegisteredExtensions(m)
+	out := make([]int32, 0, len(exts))
+	for id := range exts {
+		out = append(out, id)
+	}
+	return out, nil
+}
+
+// fileDescEncodingByFilename finds the file descriptor for given filename,
+// does marshalling on it and returns the marshalled result.
+func (s *serverReflectionServer) fileDescEncodingByFilename(name string) ([]byte, error) {
+	enc := proto.FileDescriptor(name)
+	if enc == nil {
+		return nil, fmt.Errorf("unknown file: %v", name)
+	}
+	fd, err := decodeFileDesc(enc)
+	if err != nil {
+		return nil, err
+	}
+	return proto.Marshal(fd)
+}
+
+// parseMetadata finds the file descriptor bytes specified meta.
+// For SupportPackageIsVersion4, m is the name of the proto file, we
+// call proto.FileDescriptor to get the byte slice.
+// For SupportPackageIsVersion3, m is a byte slice itself.
+func parseMetadata(meta interface{}) ([]byte, bool) {
+	// Check if meta is the file name.
+	if fileNameForMeta, ok := meta.(string); ok {
+		return proto.FileDescriptor(fileNameForMeta), true
+	}
+
+	// Check if meta is the byte slice.
+	if enc, ok := meta.([]byte); ok {
+		return enc, true
+	}
+
+	return nil, false
+}
+
+// fileDescEncodingContainingSymbol finds the file descriptor containing the given symbol,
+// does marshalling on it and returns the marshalled result.
+// The given symbol can be a type, a service or a method.
+func (s *serverReflectionServer) fileDescEncodingContainingSymbol(name string) ([]byte, error) {
+	_, symbols := s.getSymbols()
+	fd := symbols[name]
+	if fd == nil {
+		// Check if it's a type name that was not present in the
+		// transitive dependencies of the registered services.
+		if st, err := typeForName(name); err == nil {
+			fd, err = s.fileDescForType(st)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	if fd == nil {
+		return nil, fmt.Errorf("unknown symbol: %v", name)
+	}
+
+	return proto.Marshal(fd)
+}
+
+// fileDescEncodingContainingExtension finds the file descriptor containing given extension,
+// does marshalling on it and returns the marshalled result.
+func (s *serverReflectionServer) fileDescEncodingContainingExtension(typeName string, extNum int32) ([]byte, error) {
+	st, err := typeForName(typeName)
+	if err != nil {
+		return nil, err
+	}
+	fd, err := fileDescContainingExtension(st, extNum)
+	if err != nil {
+		return nil, err
+	}
+	return proto.Marshal(fd)
+}
+
+// allExtensionNumbersForTypeName returns all extension numbers for the given type.
+func (s *serverReflectionServer) allExtensionNumbersForTypeName(name string) ([]int32, error) {
+	st, err := typeForName(name)
+	if err != nil {
+		return nil, err
+	}
+	extNums, err := s.allExtensionNumbersForType(st)
+	if err != nil {
+		return nil, err
+	}
+	return extNums, nil
+}
+
+// ServerReflectionInfo is the reflection service handler.
+func (s *serverReflectionServer) ServerReflectionInfo(stream rpb.ServerReflection_ServerReflectionInfoServer) error {
+	for {
+		in, err := stream.Recv()
+		if err == io.EOF {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+
+		out := &rpb.ServerReflectionResponse{
+			ValidHost:       in.Host,
+			OriginalRequest: in,
+		}
+		switch req := in.MessageRequest.(type) {
+		case *rpb.ServerReflectionRequest_FileByFilename:
+			b, err := s.fileDescEncodingByFilename(req.FileByFilename)
+			if err != nil {
+				out.MessageResponse = &rpb.ServerReflectionResponse_ErrorResponse{
+					ErrorResponse: &rpb.ErrorResponse{
+						ErrorCode:    int32(codes.NotFound),
+						ErrorMessage: err.Error(),
+					},
+				}
+			} else {
+				out.MessageResponse = &rpb.ServerReflectionResponse_FileDescriptorResponse{
+					FileDescriptorResponse: &rpb.FileDescriptorResponse{FileDescriptorProto: [][]byte{b}},
+				}
+			}
+		case *rpb.ServerReflectionRequest_FileContainingSymbol:
+			b, err := s.fileDescEncodingContainingSymbol(req.FileContainingSymbol)
+			if err != nil {
+				out.MessageResponse = &rpb.ServerReflectionResponse_ErrorResponse{
+					ErrorResponse: &rpb.ErrorResponse{
+						ErrorCode:    int32(codes.NotFound),
+						ErrorMessage: err.Error(),
+					},
+				}
+			} else {
+				out.MessageResponse = &rpb.ServerReflectionResponse_FileDescriptorResponse{
+					FileDescriptorResponse: &rpb.FileDescriptorResponse{FileDescriptorProto: [][]byte{b}},
+				}
+			}
+		case *rpb.ServerReflectionRequest_FileContainingExtension:
+			typeName := req.FileContainingExtension.ContainingType
+			extNum := req.FileContainingExtension.ExtensionNumber
+			b, err := s.fileDescEncodingContainingExtension(typeName, extNum)
+			if err != nil {
+				out.MessageResponse = &rpb.ServerReflectionResponse_ErrorResponse{
+					ErrorResponse: &rpb.ErrorResponse{
+						ErrorCode:    int32(codes.NotFound),
+						ErrorMessage: err.Error(),
+					},
+				}
+			} else {
+				out.MessageResponse = &rpb.ServerReflectionResponse_FileDescriptorResponse{
+					FileDescriptorResponse: &rpb.FileDescriptorResponse{FileDescriptorProto: [][]byte{b}},
+				}
+			}
+		case *rpb.ServerReflectionRequest_AllExtensionNumbersOfType:
+			extNums, err := s.allExtensionNumbersForTypeName(req.AllExtensionNumbersOfType)
+			if err != nil {
+				out.MessageResponse = &rpb.ServerReflectionResponse_ErrorResponse{
+					ErrorResponse: &rpb.ErrorResponse{
+						ErrorCode:    int32(codes.NotFound),
+						ErrorMessage: err.Error(),
+					},
+				}
+			} else {
+				out.MessageResponse = &rpb.ServerReflectionResponse_AllExtensionNumbersResponse{
+					AllExtensionNumbersResponse: &rpb.ExtensionNumberResponse{
+						BaseTypeName:    req.AllExtensionNumbersOfType,
+						ExtensionNumber: extNums,
+					},
+				}
+			}
+		case *rpb.ServerReflectionRequest_ListServices:
+			svcNames, _ := s.getSymbols()
+			serviceResponses := make([]*rpb.ServiceResponse, len(svcNames))
+			for i, n := range svcNames {
+				serviceResponses[i] = &rpb.ServiceResponse{
+					Name: n,
+				}
+			}
+			out.MessageResponse = &rpb.ServerReflectionResponse_ListServicesResponse{
+				ListServicesResponse: &rpb.ListServiceResponse{
+					Service: serviceResponses,
+				},
+			}
+		default:
+			return status.Errorf(codes.InvalidArgument, "invalid MessageRequest: %v", in.MessageRequest)
+		}
+
+		if err := stream.Send(out); err != nil {
+			return err
+		}
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/resolver/dns/dns_resolver.go b/go/vendor/google.golang.org/grpc/resolver/dns/dns_resolver.go
new file mode 100644
index 0000000..4af6742
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/resolver/dns/dns_resolver.go
@@ -0,0 +1,410 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package dns implements a dns resolver to be installed as the default resolver
+// in grpc.
+package dns
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/backoff"
+	"google.golang.org/grpc/internal/grpcrand"
+	"google.golang.org/grpc/resolver"
+)
+
+func init() {
+	resolver.Register(NewBuilder())
+}
+
+const (
+	defaultPort = "443"
+	defaultFreq = time.Minute * 30
+	golang      = "GO"
+	// In DNS, service config is encoded in a TXT record via the mechanism
+	// described in RFC-1464 using the attribute name grpc_config.
+	txtAttribute = "grpc_config="
+)
+
+var (
+	errMissingAddr = errors.New("dns resolver: missing address")
+
+	// Addresses ending with a colon that is supposed to be the separator
+	// between host and port is not allowed.  E.g. "::" is a valid address as
+	// it is an IPv6 address (host only) and "[::]:" is invalid as it ends with
+	// a colon as the host and port separator
+	errEndsWithColon = errors.New("dns resolver: missing port after port-separator colon")
+)
+
+// NewBuilder creates a dnsBuilder which is used to factory DNS resolvers.
+func NewBuilder() resolver.Builder {
+	return &dnsBuilder{minFreq: defaultFreq}
+}
+
+type dnsBuilder struct {
+	// minimum frequency of polling the DNS server.
+	minFreq time.Duration
+}
+
+// Build creates and starts a DNS resolver that watches the name resolution of the target.
+func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
+	host, port, err := parseTarget(target.Endpoint, defaultPort)
+	if err != nil {
+		return nil, err
+	}
+
+	// IP address.
+	if net.ParseIP(host) != nil {
+		host, _ = formatIP(host)
+		addr := []resolver.Address{{Addr: host + ":" + port}}
+		i := &ipResolver{
+			cc: cc,
+			ip: addr,
+			rn: make(chan struct{}, 1),
+			q:  make(chan struct{}),
+		}
+		cc.NewAddress(addr)
+		go i.watcher()
+		return i, nil
+	}
+
+	// DNS address (non-IP).
+	ctx, cancel := context.WithCancel(context.Background())
+	d := &dnsResolver{
+		freq:                 b.minFreq,
+		backoff:              backoff.Exponential{MaxDelay: b.minFreq},
+		host:                 host,
+		port:                 port,
+		ctx:                  ctx,
+		cancel:               cancel,
+		cc:                   cc,
+		t:                    time.NewTimer(0),
+		rn:                   make(chan struct{}, 1),
+		disableServiceConfig: opts.DisableServiceConfig,
+	}
+
+	if target.Authority == "" {
+		d.resolver = defaultResolver
+	} else {
+		d.resolver, err = customAuthorityResolver(target.Authority)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	d.wg.Add(1)
+	go d.watcher()
+	return d, nil
+}
+
+// Scheme returns the naming scheme of this resolver builder, which is "dns".
+func (b *dnsBuilder) Scheme() string {
+	return "dns"
+}
+
+type netResolver interface {
+	LookupHost(ctx context.Context, host string) (addrs []string, err error)
+	LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error)
+	LookupTXT(ctx context.Context, name string) (txts []string, err error)
+}
+
+// ipResolver watches for the name resolution update for an IP address.
+type ipResolver struct {
+	cc resolver.ClientConn
+	ip []resolver.Address
+	// rn channel is used by ResolveNow() to force an immediate resolution of the target.
+	rn chan struct{}
+	q  chan struct{}
+}
+
+// ResolveNow resend the address it stores, no resolution is needed.
+func (i *ipResolver) ResolveNow(opt resolver.ResolveNowOption) {
+	select {
+	case i.rn <- struct{}{}:
+	default:
+	}
+}
+
+// Close closes the ipResolver.
+func (i *ipResolver) Close() {
+	close(i.q)
+}
+
+func (i *ipResolver) watcher() {
+	for {
+		select {
+		case <-i.rn:
+			i.cc.NewAddress(i.ip)
+		case <-i.q:
+			return
+		}
+	}
+}
+
+// dnsResolver watches for the name resolution update for a non-IP target.
+type dnsResolver struct {
+	freq       time.Duration
+	backoff    backoff.Exponential
+	retryCount int
+	host       string
+	port       string
+	resolver   netResolver
+	ctx        context.Context
+	cancel     context.CancelFunc
+	cc         resolver.ClientConn
+	// rn channel is used by ResolveNow() to force an immediate resolution of the target.
+	rn chan struct{}
+	t  *time.Timer
+	// wg is used to enforce Close() to return after the watcher() goroutine has finished.
+	// Otherwise, data race will be possible. [Race Example] in dns_resolver_test we
+	// replace the real lookup functions with mocked ones to facilitate testing.
+	// If Close() doesn't wait for watcher() goroutine finishes, race detector sometimes
+	// will warns lookup (READ the lookup function pointers) inside watcher() goroutine
+	// has data race with replaceNetFunc (WRITE the lookup function pointers).
+	wg                   sync.WaitGroup
+	disableServiceConfig bool
+}
+
+// ResolveNow invoke an immediate resolution of the target that this dnsResolver watches.
+func (d *dnsResolver) ResolveNow(opt resolver.ResolveNowOption) {
+	select {
+	case d.rn <- struct{}{}:
+	default:
+	}
+}
+
+// Close closes the dnsResolver.
+func (d *dnsResolver) Close() {
+	d.cancel()
+	d.wg.Wait()
+	d.t.Stop()
+}
+
+func (d *dnsResolver) watcher() {
+	defer d.wg.Done()
+	for {
+		select {
+		case <-d.ctx.Done():
+			return
+		case <-d.t.C:
+		case <-d.rn:
+		}
+		result, sc := d.lookup()
+		// Next lookup should happen within an interval defined by d.freq. It may be
+		// more often due to exponential retry on empty address list.
+		if len(result) == 0 {
+			d.retryCount++
+			d.t.Reset(d.backoff.Backoff(d.retryCount))
+		} else {
+			d.retryCount = 0
+			d.t.Reset(d.freq)
+		}
+		d.cc.NewServiceConfig(sc)
+		d.cc.NewAddress(result)
+	}
+}
+
+func (d *dnsResolver) lookupSRV() []resolver.Address {
+	var newAddrs []resolver.Address
+	_, srvs, err := d.resolver.LookupSRV(d.ctx, "grpclb", "tcp", d.host)
+	if err != nil {
+		grpclog.Infof("grpc: failed dns SRV record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, s := range srvs {
+		lbAddrs, err := d.resolver.LookupHost(d.ctx, s.Target)
+		if err != nil {
+			grpclog.Infof("grpc: failed load balancer address dns lookup due to %v.\n", err)
+			continue
+		}
+		for _, a := range lbAddrs {
+			a, ok := formatIP(a)
+			if !ok {
+				grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+				continue
+			}
+			addr := a + ":" + strconv.Itoa(int(s.Port))
+			newAddrs = append(newAddrs, resolver.Address{Addr: addr, Type: resolver.GRPCLB, ServerName: s.Target})
+		}
+	}
+	return newAddrs
+}
+
+func (d *dnsResolver) lookupTXT() string {
+	ss, err := d.resolver.LookupTXT(d.ctx, d.host)
+	if err != nil {
+		grpclog.Infof("grpc: failed dns TXT record lookup due to %v.\n", err)
+		return ""
+	}
+	var res string
+	for _, s := range ss {
+		res += s
+	}
+
+	// TXT record must have "grpc_config=" attribute in order to be used as service config.
+	if !strings.HasPrefix(res, txtAttribute) {
+		grpclog.Warningf("grpc: TXT record %v missing %v attribute", res, txtAttribute)
+		return ""
+	}
+	return strings.TrimPrefix(res, txtAttribute)
+}
+
+func (d *dnsResolver) lookupHost() []resolver.Address {
+	var newAddrs []resolver.Address
+	addrs, err := d.resolver.LookupHost(d.ctx, d.host)
+	if err != nil {
+		grpclog.Warningf("grpc: failed dns A record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, a := range addrs {
+		a, ok := formatIP(a)
+		if !ok {
+			grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+			continue
+		}
+		addr := a + ":" + d.port
+		newAddrs = append(newAddrs, resolver.Address{Addr: addr})
+	}
+	return newAddrs
+}
+
+func (d *dnsResolver) lookup() ([]resolver.Address, string) {
+	newAddrs := d.lookupSRV()
+	// Support fallback to non-balancer address.
+	newAddrs = append(newAddrs, d.lookupHost()...)
+	if d.disableServiceConfig {
+		return newAddrs, ""
+	}
+	sc := d.lookupTXT()
+	return newAddrs, canaryingSC(sc)
+}
+
+// formatIP returns ok = false if addr is not a valid textual representation of an IP address.
+// If addr is an IPv4 address, return the addr and ok = true.
+// If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true.
+func formatIP(addr string) (addrIP string, ok bool) {
+	ip := net.ParseIP(addr)
+	if ip == nil {
+		return "", false
+	}
+	if ip.To4() != nil {
+		return addr, true
+	}
+	return "[" + addr + "]", true
+}
+
+// parseTarget takes the user input target string and default port, returns formatted host and port info.
+// If target doesn't specify a port, set the port to be the defaultPort.
+// If target is in IPv6 format and host-name is enclosed in sqarue brackets, brackets
+// are strippd when setting the host.
+// examples:
+// target: "www.google.com" defaultPort: "443" returns host: "www.google.com", port: "443"
+// target: "ipv4-host:80" defaultPort: "443" returns host: "ipv4-host", port: "80"
+// target: "[ipv6-host]" defaultPort: "443" returns host: "ipv6-host", port: "443"
+// target: ":80" defaultPort: "443" returns host: "localhost", port: "80"
+func parseTarget(target, defaultPort string) (host, port string, err error) {
+	if target == "" {
+		return "", "", errMissingAddr
+	}
+	if ip := net.ParseIP(target); ip != nil {
+		// target is an IPv4 or IPv6(without brackets) address
+		return target, defaultPort, nil
+	}
+	if host, port, err = net.SplitHostPort(target); err == nil {
+		if port == "" {
+			// If the port field is empty (target ends with colon), e.g. "[::1]:", this is an error.
+			return "", "", errEndsWithColon
+		}
+		// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
+		if host == "" {
+			// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
+			host = "localhost"
+		}
+		return host, port, nil
+	}
+	if host, port, err = net.SplitHostPort(target + ":" + defaultPort); err == nil {
+		// target doesn't have port
+		return host, port, nil
+	}
+	return "", "", fmt.Errorf("invalid target address %v, error info: %v", target, err)
+}
+
+type rawChoice struct {
+	ClientLanguage *[]string        `json:"clientLanguage,omitempty"`
+	Percentage     *int             `json:"percentage,omitempty"`
+	ClientHostName *[]string        `json:"clientHostName,omitempty"`
+	ServiceConfig  *json.RawMessage `json:"serviceConfig,omitempty"`
+}
+
+func containsString(a *[]string, b string) bool {
+	if a == nil {
+		return true
+	}
+	for _, c := range *a {
+		if c == b {
+			return true
+		}
+	}
+	return false
+}
+
+func chosenByPercentage(a *int) bool {
+	if a == nil {
+		return true
+	}
+	return grpcrand.Intn(100)+1 <= *a
+}
+
+func canaryingSC(js string) string {
+	if js == "" {
+		return ""
+	}
+	var rcs []rawChoice
+	err := json.Unmarshal([]byte(js), &rcs)
+	if err != nil {
+		grpclog.Warningf("grpc: failed to parse service config json string due to %v.\n", err)
+		return ""
+	}
+	cliHostname, err := os.Hostname()
+	if err != nil {
+		grpclog.Warningf("grpc: failed to get client hostname due to %v.\n", err)
+		return ""
+	}
+	var sc string
+	for _, c := range rcs {
+		if !containsString(c.ClientLanguage, golang) ||
+			!chosenByPercentage(c.Percentage) ||
+			!containsString(c.ClientHostName, cliHostname) ||
+			c.ServiceConfig == nil {
+			continue
+		}
+		sc = string(*c.ServiceConfig)
+		break
+	}
+	return sc
+}
diff --git a/go/vendor/google.golang.org/grpc/resolver/dns/go19.go b/go/vendor/google.golang.org/grpc/resolver/dns/go19.go
new file mode 100644
index 0000000..9886de2
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/resolver/dns/go19.go
@@ -0,0 +1,54 @@
+// +build go1.9
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import (
+	"net"
+
+	"golang.org/x/net/context"
+)
+
+var (
+	defaultResolver netResolver = net.DefaultResolver
+)
+
+const defaultDNSSvrPort = "53"
+
+var customAuthorityDialler = func(authority string) func(ctx context.Context, network, address string) (net.Conn, error) {
+	return func(ctx context.Context, network, address string) (net.Conn, error) {
+		var dialer net.Dialer
+		return dialer.DialContext(ctx, network, authority)
+	}
+}
+
+var customAuthorityResolver = func(authority string) (netResolver, error) {
+	host, port, err := parseTarget(authority, defaultDNSSvrPort)
+	if err != nil {
+		return nil, err
+	}
+
+	authorityWithPort := net.JoinHostPort(host, port)
+
+	return &net.Resolver{
+		PreferGo: true,
+		Dial:     customAuthorityDialler(authorityWithPort),
+	}, nil
+}
diff --git a/go/vendor/google.golang.org/grpc/resolver/dns/pre_go19.go b/go/vendor/google.golang.org/grpc/resolver/dns/pre_go19.go
new file mode 100644
index 0000000..7042811
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/resolver/dns/pre_go19.go
@@ -0,0 +1,51 @@
+// +build go1.6, !go1.9
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import (
+	"fmt"
+	"net"
+
+	"golang.org/x/net/context"
+)
+
+var (
+	defaultResolver netResolver = &preGo19Resolver{}
+)
+
+type preGo19Resolver struct {
+}
+
+func (*preGo19Resolver) LookupHost(ctx context.Context, host string) ([]string, error) {
+	return net.LookupHost(host)
+}
+
+func (*preGo19Resolver) LookupSRV(ctx context.Context, service, proto, name string) (string, []*net.SRV, error) {
+	return net.LookupSRV(service, proto, name)
+}
+
+func (*preGo19Resolver) LookupTXT(ctx context.Context, name string) ([]string, error) {
+	return net.LookupTXT(name)
+}
+
+var customAuthorityResolver = func(authority string) (netResolver, error) {
+	return nil, fmt.Errorf("Default DNS resolver does not support custom DNS server with go < 1.9")
+}
diff --git a/go/vendor/google.golang.org/grpc/resolver/passthrough/passthrough.go b/go/vendor/google.golang.org/grpc/resolver/passthrough/passthrough.go
new file mode 100644
index 0000000..b76010d
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/resolver/passthrough/passthrough.go
@@ -0,0 +1,57 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package passthrough implements a pass-through resolver. It sends the target
+// name without scheme back to gRPC as resolved address.
+package passthrough
+
+import "google.golang.org/grpc/resolver"
+
+const scheme = "passthrough"
+
+type passthroughBuilder struct{}
+
+func (*passthroughBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
+	r := &passthroughResolver{
+		target: target,
+		cc:     cc,
+	}
+	r.start()
+	return r, nil
+}
+
+func (*passthroughBuilder) Scheme() string {
+	return scheme
+}
+
+type passthroughResolver struct {
+	target resolver.Target
+	cc     resolver.ClientConn
+}
+
+func (r *passthroughResolver) start() {
+	r.cc.NewAddress([]resolver.Address{{Addr: r.target.Endpoint}})
+}
+
+func (*passthroughResolver) ResolveNow(o resolver.ResolveNowOption) {}
+
+func (*passthroughResolver) Close() {}
+
+func init() {
+	resolver.Register(&passthroughBuilder{})
+}
diff --git a/go/vendor/google.golang.org/grpc/resolver/resolver.go b/go/vendor/google.golang.org/grpc/resolver/resolver.go
new file mode 100644
index 0000000..145cf47
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/resolver/resolver.go
@@ -0,0 +1,158 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package resolver defines APIs for name resolution in gRPC.
+// All APIs in this package are experimental.
+package resolver
+
+var (
+	// m is a map from scheme to resolver builder.
+	m = make(map[string]Builder)
+	// defaultScheme is the default scheme to use.
+	defaultScheme = "passthrough"
+)
+
+// TODO(bar) install dns resolver in init(){}.
+
+// Register registers the resolver builder to the resolver map. b.Scheme will be
+// used as the scheme registered with this builder.
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. If multiple Resolvers are
+// registered with the same name, the one registered last will take effect.
+func Register(b Builder) {
+	m[b.Scheme()] = b
+}
+
+// Get returns the resolver builder registered with the given scheme.
+//
+// If no builder is register with the scheme, nil will be returned.
+func Get(scheme string) Builder {
+	if b, ok := m[scheme]; ok {
+		return b
+	}
+	return nil
+}
+
+// SetDefaultScheme sets the default scheme that will be used. The default
+// default scheme is "passthrough".
+//
+// NOTE: this function must only be called during initialization time (i.e. in
+// an init() function), and is not thread-safe. The scheme set last overrides
+// previously set values.
+func SetDefaultScheme(scheme string) {
+	defaultScheme = scheme
+}
+
+// GetDefaultScheme gets the default scheme that will be used.
+func GetDefaultScheme() string {
+	return defaultScheme
+}
+
+// AddressType indicates the address type returned by name resolution.
+type AddressType uint8
+
+const (
+	// Backend indicates the address is for a backend server.
+	Backend AddressType = iota
+	// GRPCLB indicates the address is for a grpclb load balancer.
+	GRPCLB
+)
+
+// Address represents a server the client connects to.
+// This is the EXPERIMENTAL API and may be changed or extended in the future.
+type Address struct {
+	// Addr is the server address on which a connection will be established.
+	Addr string
+	// Type is the type of this address.
+	Type AddressType
+	// ServerName is the name of this address.
+	//
+	// e.g. if Type is GRPCLB, ServerName should be the name of the remote load
+	// balancer, not the name of the backend.
+	ServerName string
+	// Metadata is the information associated with Addr, which may be used
+	// to make load balancing decision.
+	Metadata interface{}
+}
+
+// BuildOption includes additional information for the builder to create
+// the resolver.
+type BuildOption struct {
+	// DisableServiceConfig indicates whether resolver should fetch service config data.
+	DisableServiceConfig bool
+}
+
+// ClientConn contains the callbacks for resolver to notify any updates
+// to the gRPC ClientConn.
+//
+// This interface is to be implemented by gRPC. Users should not need a
+// brand new implementation of this interface. For the situations like
+// testing, the new implementation should embed this interface. This allows
+// gRPC to add new methods to this interface.
+type ClientConn interface {
+	// NewAddress is called by resolver to notify ClientConn a new list
+	// of resolved addresses.
+	// The address list should be the complete list of resolved addresses.
+	NewAddress(addresses []Address)
+	// NewServiceConfig is called by resolver to notify ClientConn a new
+	// service config. The service config should be provided as a json string.
+	NewServiceConfig(serviceConfig string)
+}
+
+// Target represents a target for gRPC, as specified in:
+// https://github.com/grpc/grpc/blob/master/doc/naming.md.
+type Target struct {
+	Scheme    string
+	Authority string
+	Endpoint  string
+}
+
+// Builder creates a resolver that will be used to watch name resolution updates.
+type Builder interface {
+	// Build creates a new resolver for the given target.
+	//
+	// gRPC dial calls Build synchronously, and fails if the returned error is
+	// not nil.
+	Build(target Target, cc ClientConn, opts BuildOption) (Resolver, error)
+	// Scheme returns the scheme supported by this resolver.
+	// Scheme is defined at https://github.com/grpc/grpc/blob/master/doc/naming.md.
+	Scheme() string
+}
+
+// ResolveNowOption includes additional information for ResolveNow.
+type ResolveNowOption struct{}
+
+// Resolver watches for the updates on the specified target.
+// Updates include address updates and service config updates.
+type Resolver interface {
+	// ResolveNow will be called by gRPC to try to resolve the target name
+	// again. It's just a hint, resolver can ignore this if it's not necessary.
+	//
+	// It could be called multiple times concurrently.
+	ResolveNow(ResolveNowOption)
+	// Close closes the resolver.
+	Close()
+}
+
+// UnregisterForTesting removes the resolver builder with the given scheme from the
+// resolver map.
+// This function is for testing only.
+func UnregisterForTesting(scheme string) {
+	delete(m, scheme)
+}
diff --git a/go/vendor/google.golang.org/grpc/resolver_conn_wrapper.go b/go/vendor/google.golang.org/grpc/resolver_conn_wrapper.go
new file mode 100644
index 0000000..a6c02ac
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/resolver_conn_wrapper.go
@@ -0,0 +1,189 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"fmt"
+	"strings"
+
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/resolver"
+)
+
+// ccResolverWrapper is a wrapper on top of cc for resolvers.
+// It implements resolver.ClientConnection interface.
+type ccResolverWrapper struct {
+	cc                 *ClientConn
+	resolver           resolver.Resolver
+	addrCh             chan []resolver.Address
+	scCh               chan string
+	done               chan struct{}
+	lastAddressesCount int
+}
+
+// split2 returns the values from strings.SplitN(s, sep, 2).
+// If sep is not found, it returns ("", s, false) instead.
+func split2(s, sep string) (string, string, bool) {
+	spl := strings.SplitN(s, sep, 2)
+	if len(spl) < 2 {
+		return "", "", false
+	}
+	return spl[0], spl[1], true
+}
+
+// parseTarget splits target into a struct containing scheme, authority and
+// endpoint.
+//
+// If target is not a valid scheme://authority/endpoint, it returns {Endpoint:
+// target}.
+func parseTarget(target string) (ret resolver.Target) {
+	var ok bool
+	ret.Scheme, ret.Endpoint, ok = split2(target, "://")
+	if !ok {
+		return resolver.Target{Endpoint: target}
+	}
+	ret.Authority, ret.Endpoint, ok = split2(ret.Endpoint, "/")
+	if !ok {
+		return resolver.Target{Endpoint: target}
+	}
+	return ret
+}
+
+// newCCResolverWrapper parses cc.target for scheme and gets the resolver
+// builder for this scheme and builds the resolver. The monitoring goroutine
+// for it is not started yet and can be created by calling start().
+//
+// If withResolverBuilder dial option is set, the specified resolver will be
+// used instead.
+func newCCResolverWrapper(cc *ClientConn) (*ccResolverWrapper, error) {
+	rb := cc.dopts.resolverBuilder
+	if rb == nil {
+		return nil, fmt.Errorf("could not get resolver for scheme: %q", cc.parsedTarget.Scheme)
+	}
+
+	ccr := &ccResolverWrapper{
+		cc:     cc,
+		addrCh: make(chan []resolver.Address, 1),
+		scCh:   make(chan string, 1),
+		done:   make(chan struct{}),
+	}
+
+	var err error
+	ccr.resolver, err = rb.Build(cc.parsedTarget, ccr, resolver.BuildOption{DisableServiceConfig: cc.dopts.disableServiceConfig})
+	if err != nil {
+		return nil, err
+	}
+	return ccr, nil
+}
+
+func (ccr *ccResolverWrapper) start() {
+	go ccr.watcher()
+}
+
+// watcher processes address updates and service config updates sequentially.
+// Otherwise, we need to resolve possible races between address and service
+// config (e.g. they specify different balancer types).
+func (ccr *ccResolverWrapper) watcher() {
+	for {
+		select {
+		case <-ccr.done:
+			return
+		default:
+		}
+
+		select {
+		case addrs := <-ccr.addrCh:
+			select {
+			case <-ccr.done:
+				return
+			default:
+			}
+			grpclog.Infof("ccResolverWrapper: sending new addresses to cc: %v", addrs)
+			if channelz.IsOn() {
+				ccr.addChannelzTraceEvent(addrs)
+			}
+			ccr.cc.handleResolvedAddrs(addrs, nil)
+		case sc := <-ccr.scCh:
+			select {
+			case <-ccr.done:
+				return
+			default:
+			}
+			grpclog.Infof("ccResolverWrapper: got new service config: %v", sc)
+			ccr.cc.handleServiceConfig(sc)
+		case <-ccr.done:
+			return
+		}
+	}
+}
+
+func (ccr *ccResolverWrapper) resolveNow(o resolver.ResolveNowOption) {
+	ccr.resolver.ResolveNow(o)
+}
+
+func (ccr *ccResolverWrapper) close() {
+	ccr.resolver.Close()
+	close(ccr.done)
+}
+
+// NewAddress is called by the resolver implemenetion to send addresses to gRPC.
+func (ccr *ccResolverWrapper) NewAddress(addrs []resolver.Address) {
+	select {
+	case <-ccr.addrCh:
+	default:
+	}
+	ccr.addrCh <- addrs
+}
+
+// NewServiceConfig is called by the resolver implemenetion to send service
+// configs to gRPC.
+func (ccr *ccResolverWrapper) NewServiceConfig(sc string) {
+	select {
+	case <-ccr.scCh:
+	default:
+	}
+	ccr.scCh <- sc
+}
+
+func (ccr *ccResolverWrapper) addChannelzTraceEvent(addrs []resolver.Address) {
+	if len(addrs) == 0 && ccr.lastAddressesCount != 0 {
+		channelz.AddTraceEvent(ccr.cc.channelzID, &channelz.TraceEventDesc{
+			Desc:     "Resolver returns an empty address list",
+			Severity: channelz.CtWarning,
+		})
+	} else if len(addrs) != 0 && ccr.lastAddressesCount == 0 {
+		var s string
+		for i, a := range addrs {
+			if a.ServerName != "" {
+				s += a.Addr + "(" + a.ServerName + ")"
+			} else {
+				s += a.Addr
+			}
+			if i != len(addrs)-1 {
+				s += " "
+			}
+		}
+		channelz.AddTraceEvent(ccr.cc.channelzID, &channelz.TraceEventDesc{
+			Desc:     fmt.Sprintf("Resolver returns a non-empty address list (previous one was empty) %q", s),
+			Severity: channelz.CtINFO,
+		})
+	}
+	ccr.lastAddressesCount = len(addrs)
+}
diff --git a/go/vendor/google.golang.org/grpc/rpc_util.go b/go/vendor/google.golang.org/grpc/rpc_util.go
new file mode 100644
index 0000000..6849e37
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/rpc_util.go
@@ -0,0 +1,789 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"bytes"
+	"compress/gzip"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/encoding"
+	"google.golang.org/grpc/encoding/proto"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+)
+
+// Compressor defines the interface gRPC uses to compress a message.
+//
+// Deprecated: use package encoding.
+type Compressor interface {
+	// Do compresses p into w.
+	Do(w io.Writer, p []byte) error
+	// Type returns the compression algorithm the Compressor uses.
+	Type() string
+}
+
+type gzipCompressor struct {
+	pool sync.Pool
+}
+
+// NewGZIPCompressor creates a Compressor based on GZIP.
+//
+// Deprecated: use package encoding/gzip.
+func NewGZIPCompressor() Compressor {
+	c, _ := NewGZIPCompressorWithLevel(gzip.DefaultCompression)
+	return c
+}
+
+// NewGZIPCompressorWithLevel is like NewGZIPCompressor but specifies the gzip compression level instead
+// of assuming DefaultCompression.
+//
+// The error returned will be nil if the level is valid.
+//
+// Deprecated: use package encoding/gzip.
+func NewGZIPCompressorWithLevel(level int) (Compressor, error) {
+	if level < gzip.DefaultCompression || level > gzip.BestCompression {
+		return nil, fmt.Errorf("grpc: invalid compression level: %d", level)
+	}
+	return &gzipCompressor{
+		pool: sync.Pool{
+			New: func() interface{} {
+				w, err := gzip.NewWriterLevel(ioutil.Discard, level)
+				if err != nil {
+					panic(err)
+				}
+				return w
+			},
+		},
+	}, nil
+}
+
+func (c *gzipCompressor) Do(w io.Writer, p []byte) error {
+	z := c.pool.Get().(*gzip.Writer)
+	defer c.pool.Put(z)
+	z.Reset(w)
+	if _, err := z.Write(p); err != nil {
+		return err
+	}
+	return z.Close()
+}
+
+func (c *gzipCompressor) Type() string {
+	return "gzip"
+}
+
+// Decompressor defines the interface gRPC uses to decompress a message.
+//
+// Deprecated: use package encoding.
+type Decompressor interface {
+	// Do reads the data from r and uncompress them.
+	Do(r io.Reader) ([]byte, error)
+	// Type returns the compression algorithm the Decompressor uses.
+	Type() string
+}
+
+type gzipDecompressor struct {
+	pool sync.Pool
+}
+
+// NewGZIPDecompressor creates a Decompressor based on GZIP.
+//
+// Deprecated: use package encoding/gzip.
+func NewGZIPDecompressor() Decompressor {
+	return &gzipDecompressor{}
+}
+
+func (d *gzipDecompressor) Do(r io.Reader) ([]byte, error) {
+	var z *gzip.Reader
+	switch maybeZ := d.pool.Get().(type) {
+	case nil:
+		newZ, err := gzip.NewReader(r)
+		if err != nil {
+			return nil, err
+		}
+		z = newZ
+	case *gzip.Reader:
+		z = maybeZ
+		if err := z.Reset(r); err != nil {
+			d.pool.Put(z)
+			return nil, err
+		}
+	}
+
+	defer func() {
+		z.Close()
+		d.pool.Put(z)
+	}()
+	return ioutil.ReadAll(z)
+}
+
+func (d *gzipDecompressor) Type() string {
+	return "gzip"
+}
+
+// callInfo contains all related configuration and information about an RPC.
+type callInfo struct {
+	compressorType        string
+	failFast              bool
+	stream                *clientStream
+	maxReceiveMessageSize *int
+	maxSendMessageSize    *int
+	creds                 credentials.PerRPCCredentials
+	contentSubtype        string
+	codec                 baseCodec
+	maxRetryRPCBufferSize int
+}
+
+func defaultCallInfo() *callInfo {
+	return &callInfo{
+		failFast:              true,
+		maxRetryRPCBufferSize: 256 * 1024, // 256KB
+	}
+}
+
+// CallOption configures a Call before it starts or extracts information from
+// a Call after it completes.
+type CallOption interface {
+	// before is called before the call is sent to any server.  If before
+	// returns a non-nil error, the RPC fails with that error.
+	before(*callInfo) error
+
+	// after is called after the call has completed.  after cannot return an
+	// error, so any failures should be reported via output parameters.
+	after(*callInfo)
+}
+
+// EmptyCallOption does not alter the Call configuration.
+// It can be embedded in another structure to carry satellite data for use
+// by interceptors.
+type EmptyCallOption struct{}
+
+func (EmptyCallOption) before(*callInfo) error { return nil }
+func (EmptyCallOption) after(*callInfo)        {}
+
+// Header returns a CallOptions that retrieves the header metadata
+// for a unary RPC.
+func Header(md *metadata.MD) CallOption {
+	return HeaderCallOption{HeaderAddr: md}
+}
+
+// HeaderCallOption is a CallOption for collecting response header metadata.
+// The metadata field will be populated *after* the RPC completes.
+// This is an EXPERIMENTAL API.
+type HeaderCallOption struct {
+	HeaderAddr *metadata.MD
+}
+
+func (o HeaderCallOption) before(c *callInfo) error { return nil }
+func (o HeaderCallOption) after(c *callInfo) {
+	if c.stream != nil {
+		*o.HeaderAddr, _ = c.stream.Header()
+	}
+}
+
+// Trailer returns a CallOptions that retrieves the trailer metadata
+// for a unary RPC.
+func Trailer(md *metadata.MD) CallOption {
+	return TrailerCallOption{TrailerAddr: md}
+}
+
+// TrailerCallOption is a CallOption for collecting response trailer metadata.
+// The metadata field will be populated *after* the RPC completes.
+// This is an EXPERIMENTAL API.
+type TrailerCallOption struct {
+	TrailerAddr *metadata.MD
+}
+
+func (o TrailerCallOption) before(c *callInfo) error { return nil }
+func (o TrailerCallOption) after(c *callInfo) {
+	if c.stream != nil {
+		*o.TrailerAddr = c.stream.Trailer()
+	}
+}
+
+// Peer returns a CallOption that retrieves peer information for a unary RPC.
+// The peer field will be populated *after* the RPC completes.
+func Peer(p *peer.Peer) CallOption {
+	return PeerCallOption{PeerAddr: p}
+}
+
+// PeerCallOption is a CallOption for collecting the identity of the remote
+// peer. The peer field will be populated *after* the RPC completes.
+// This is an EXPERIMENTAL API.
+type PeerCallOption struct {
+	PeerAddr *peer.Peer
+}
+
+func (o PeerCallOption) before(c *callInfo) error { return nil }
+func (o PeerCallOption) after(c *callInfo) {
+	if c.stream != nil {
+		if x, ok := peer.FromContext(c.stream.Context()); ok {
+			*o.PeerAddr = *x
+		}
+	}
+}
+
+// FailFast configures the action to take when an RPC is attempted on broken
+// connections or unreachable servers.  If failFast is true, the RPC will fail
+// immediately. Otherwise, the RPC client will block the call until a
+// connection is available (or the call is canceled or times out) and will
+// retry the call if it fails due to a transient error.  gRPC will not retry if
+// data was written to the wire unless the server indicates it did not process
+// the data.  Please refer to
+// https://github.com/grpc/grpc/blob/master/doc/wait-for-ready.md.
+//
+// By default, RPCs are "Fail Fast".
+func FailFast(failFast bool) CallOption {
+	return FailFastCallOption{FailFast: failFast}
+}
+
+// FailFastCallOption is a CallOption for indicating whether an RPC should fail
+// fast or not.
+// This is an EXPERIMENTAL API.
+type FailFastCallOption struct {
+	FailFast bool
+}
+
+func (o FailFastCallOption) before(c *callInfo) error {
+	c.failFast = o.FailFast
+	return nil
+}
+func (o FailFastCallOption) after(c *callInfo) {}
+
+// MaxCallRecvMsgSize returns a CallOption which sets the maximum message size the client can receive.
+func MaxCallRecvMsgSize(s int) CallOption {
+	return MaxRecvMsgSizeCallOption{MaxRecvMsgSize: s}
+}
+
+// MaxRecvMsgSizeCallOption is a CallOption that indicates the maximum message
+// size the client can receive.
+// This is an EXPERIMENTAL API.
+type MaxRecvMsgSizeCallOption struct {
+	MaxRecvMsgSize int
+}
+
+func (o MaxRecvMsgSizeCallOption) before(c *callInfo) error {
+	c.maxReceiveMessageSize = &o.MaxRecvMsgSize
+	return nil
+}
+func (o MaxRecvMsgSizeCallOption) after(c *callInfo) {}
+
+// MaxCallSendMsgSize returns a CallOption which sets the maximum message size the client can send.
+func MaxCallSendMsgSize(s int) CallOption {
+	return MaxSendMsgSizeCallOption{MaxSendMsgSize: s}
+}
+
+// MaxSendMsgSizeCallOption is a CallOption that indicates the maximum message
+// size the client can send.
+// This is an EXPERIMENTAL API.
+type MaxSendMsgSizeCallOption struct {
+	MaxSendMsgSize int
+}
+
+func (o MaxSendMsgSizeCallOption) before(c *callInfo) error {
+	c.maxSendMessageSize = &o.MaxSendMsgSize
+	return nil
+}
+func (o MaxSendMsgSizeCallOption) after(c *callInfo) {}
+
+// PerRPCCredentials returns a CallOption that sets credentials.PerRPCCredentials
+// for a call.
+func PerRPCCredentials(creds credentials.PerRPCCredentials) CallOption {
+	return PerRPCCredsCallOption{Creds: creds}
+}
+
+// PerRPCCredsCallOption is a CallOption that indicates the per-RPC
+// credentials to use for the call.
+// This is an EXPERIMENTAL API.
+type PerRPCCredsCallOption struct {
+	Creds credentials.PerRPCCredentials
+}
+
+func (o PerRPCCredsCallOption) before(c *callInfo) error {
+	c.creds = o.Creds
+	return nil
+}
+func (o PerRPCCredsCallOption) after(c *callInfo) {}
+
+// UseCompressor returns a CallOption which sets the compressor used when
+// sending the request.  If WithCompressor is also set, UseCompressor has
+// higher priority.
+//
+// This API is EXPERIMENTAL.
+func UseCompressor(name string) CallOption {
+	return CompressorCallOption{CompressorType: name}
+}
+
+// CompressorCallOption is a CallOption that indicates the compressor to use.
+// This is an EXPERIMENTAL API.
+type CompressorCallOption struct {
+	CompressorType string
+}
+
+func (o CompressorCallOption) before(c *callInfo) error {
+	c.compressorType = o.CompressorType
+	return nil
+}
+func (o CompressorCallOption) after(c *callInfo) {}
+
+// CallContentSubtype returns a CallOption that will set the content-subtype
+// for a call. For example, if content-subtype is "json", the Content-Type over
+// the wire will be "application/grpc+json". The content-subtype is converted
+// to lowercase before being included in Content-Type. See Content-Type on
+// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
+// more details.
+//
+// If CallCustomCodec is not also used, the content-subtype will be used to
+// look up the Codec to use in the registry controlled by RegisterCodec. See
+// the documentation on RegisterCodec for details on registration. The lookup
+// of content-subtype is case-insensitive. If no such Codec is found, the call
+// will result in an error with code codes.Internal.
+//
+// If CallCustomCodec is also used, that Codec will be used for all request and
+// response messages, with the content-subtype set to the given contentSubtype
+// here for requests.
+func CallContentSubtype(contentSubtype string) CallOption {
+	return ContentSubtypeCallOption{ContentSubtype: strings.ToLower(contentSubtype)}
+}
+
+// ContentSubtypeCallOption is a CallOption that indicates the content-subtype
+// used for marshaling messages.
+// This is an EXPERIMENTAL API.
+type ContentSubtypeCallOption struct {
+	ContentSubtype string
+}
+
+func (o ContentSubtypeCallOption) before(c *callInfo) error {
+	c.contentSubtype = o.ContentSubtype
+	return nil
+}
+func (o ContentSubtypeCallOption) after(c *callInfo) {}
+
+// CallCustomCodec returns a CallOption that will set the given Codec to be
+// used for all request and response messages for a call. The result of calling
+// String() will be used as the content-subtype in a case-insensitive manner.
+//
+// See Content-Type on
+// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
+// more details. Also see the documentation on RegisterCodec and
+// CallContentSubtype for more details on the interaction between Codec and
+// content-subtype.
+//
+// This function is provided for advanced users; prefer to use only
+// CallContentSubtype to select a registered codec instead.
+func CallCustomCodec(codec Codec) CallOption {
+	return CustomCodecCallOption{Codec: codec}
+}
+
+// CustomCodecCallOption is a CallOption that indicates the codec used for
+// marshaling messages.
+// This is an EXPERIMENTAL API.
+type CustomCodecCallOption struct {
+	Codec Codec
+}
+
+func (o CustomCodecCallOption) before(c *callInfo) error {
+	c.codec = o.Codec
+	return nil
+}
+func (o CustomCodecCallOption) after(c *callInfo) {}
+
+// MaxRetryRPCBufferSize returns a CallOption that limits the amount of memory
+// used for buffering this RPC's requests for retry purposes.
+//
+// This API is EXPERIMENTAL.
+func MaxRetryRPCBufferSize(bytes int) CallOption {
+	return MaxRetryRPCBufferSizeCallOption{bytes}
+}
+
+// MaxRetryRPCBufferSizeCallOption is a CallOption indicating the amount of
+// memory to be used for caching this RPC for retry purposes.
+// This is an EXPERIMENTAL API.
+type MaxRetryRPCBufferSizeCallOption struct {
+	MaxRetryRPCBufferSize int
+}
+
+func (o MaxRetryRPCBufferSizeCallOption) before(c *callInfo) error {
+	c.maxRetryRPCBufferSize = o.MaxRetryRPCBufferSize
+	return nil
+}
+func (o MaxRetryRPCBufferSizeCallOption) after(c *callInfo) {}
+
+// The format of the payload: compressed or not?
+type payloadFormat uint8
+
+const (
+	compressionNone payloadFormat = 0 // no compression
+	compressionMade payloadFormat = 1 // compressed
+)
+
+// parser reads complete gRPC messages from the underlying reader.
+type parser struct {
+	// r is the underlying reader.
+	// See the comment on recvMsg for the permissible
+	// error types.
+	r io.Reader
+
+	// The header of a gRPC message. Find more detail at
+	// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
+	header [5]byte
+}
+
+// recvMsg reads a complete gRPC message from the stream.
+//
+// It returns the message and its payload (compression/encoding)
+// format. The caller owns the returned msg memory.
+//
+// If there is an error, possible values are:
+//   * io.EOF, when no messages remain
+//   * io.ErrUnexpectedEOF
+//   * of type transport.ConnectionError
+//   * an error from the status package
+// No other error values or types must be returned, which also means
+// that the underlying io.Reader must not return an incompatible
+// error.
+func (p *parser) recvMsg(maxReceiveMessageSize int) (pf payloadFormat, msg []byte, err error) {
+	if _, err := p.r.Read(p.header[:]); err != nil {
+		return 0, nil, err
+	}
+
+	pf = payloadFormat(p.header[0])
+	length := binary.BigEndian.Uint32(p.header[1:])
+
+	if length == 0 {
+		return pf, nil, nil
+	}
+	if int64(length) > int64(maxInt) {
+		return 0, nil, status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max length allowed on current machine (%d vs. %d)", length, maxInt)
+	}
+	if int(length) > maxReceiveMessageSize {
+		return 0, nil, status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max (%d vs. %d)", length, maxReceiveMessageSize)
+	}
+	// TODO(bradfitz,zhaoq): garbage. reuse buffer after proto decoding instead
+	// of making it for each message:
+	msg = make([]byte, int(length))
+	if _, err := p.r.Read(msg); err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		return 0, nil, err
+	}
+	return pf, msg, nil
+}
+
+// encode serializes msg and returns a buffer containing the message, or an
+// error if it is too large to be transmitted by grpc.  If msg is nil, it
+// generates an empty message.
+func encode(c baseCodec, msg interface{}) ([]byte, error) {
+	if msg == nil { // NOTE: typed nils will not be caught by this check
+		return nil, nil
+	}
+	b, err := c.Marshal(msg)
+	if err != nil {
+		return nil, status.Errorf(codes.Internal, "grpc: error while marshaling: %v", err.Error())
+	}
+	if uint(len(b)) > math.MaxUint32 {
+		return nil, status.Errorf(codes.ResourceExhausted, "grpc: message too large (%d bytes)", len(b))
+	}
+	return b, nil
+}
+
+// compress returns the input bytes compressed by compressor or cp.  If both
+// compressors are nil, returns nil.
+//
+// TODO(dfawley): eliminate cp parameter by wrapping Compressor in an encoding.Compressor.
+func compress(in []byte, cp Compressor, compressor encoding.Compressor) ([]byte, error) {
+	if compressor == nil && cp == nil {
+		return nil, nil
+	}
+	wrapErr := func(err error) error {
+		return status.Errorf(codes.Internal, "grpc: error while compressing: %v", err.Error())
+	}
+	cbuf := &bytes.Buffer{}
+	if compressor != nil {
+		z, err := compressor.Compress(cbuf)
+		if err != nil {
+			return nil, wrapErr(err)
+		}
+		if _, err := z.Write(in); err != nil {
+			return nil, wrapErr(err)
+		}
+		if err := z.Close(); err != nil {
+			return nil, wrapErr(err)
+		}
+	} else {
+		if err := cp.Do(cbuf, in); err != nil {
+			return nil, wrapErr(err)
+		}
+	}
+	return cbuf.Bytes(), nil
+}
+
+const (
+	payloadLen = 1
+	sizeLen    = 4
+	headerLen  = payloadLen + sizeLen
+)
+
+// msgHeader returns a 5-byte header for the message being transmitted and the
+// payload, which is compData if non-nil or data otherwise.
+func msgHeader(data, compData []byte) (hdr []byte, payload []byte) {
+	hdr = make([]byte, headerLen)
+	if compData != nil {
+		hdr[0] = byte(compressionMade)
+		data = compData
+	} else {
+		hdr[0] = byte(compressionNone)
+	}
+
+	// Write length of payload into buf
+	binary.BigEndian.PutUint32(hdr[payloadLen:], uint32(len(data)))
+	return hdr, data
+}
+
+func outPayload(client bool, msg interface{}, data, payload []byte, t time.Time) *stats.OutPayload {
+	return &stats.OutPayload{
+		Client:     client,
+		Payload:    msg,
+		Data:       data,
+		Length:     len(data),
+		WireLength: len(payload) + headerLen,
+		SentTime:   t,
+	}
+}
+
+func checkRecvPayload(pf payloadFormat, recvCompress string, haveCompressor bool) *status.Status {
+	switch pf {
+	case compressionNone:
+	case compressionMade:
+		if recvCompress == "" || recvCompress == encoding.Identity {
+			return status.New(codes.Internal, "grpc: compressed flag set with identity or empty encoding")
+		}
+		if !haveCompressor {
+			return status.Newf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", recvCompress)
+		}
+	default:
+		return status.Newf(codes.Internal, "grpc: received unexpected payload format %d", pf)
+	}
+	return nil
+}
+
+func recvAndDecompress(p *parser, s *transport.Stream, dc Decompressor, maxReceiveMessageSize int, inPayload *stats.InPayload, compressor encoding.Compressor) ([]byte, error) {
+	pf, d, err := p.recvMsg(maxReceiveMessageSize)
+	if err != nil {
+		return nil, err
+	}
+	if inPayload != nil {
+		inPayload.WireLength = len(d)
+	}
+
+	if st := checkRecvPayload(pf, s.RecvCompress(), compressor != nil || dc != nil); st != nil {
+		return nil, st.Err()
+	}
+
+	if pf == compressionMade {
+		// To match legacy behavior, if the decompressor is set by WithDecompressor or RPCDecompressor,
+		// use this decompressor as the default.
+		if dc != nil {
+			d, err = dc.Do(bytes.NewReader(d))
+			if err != nil {
+				return nil, status.Errorf(codes.Internal, "grpc: failed to decompress the received message %v", err)
+			}
+		} else {
+			dcReader, err := compressor.Decompress(bytes.NewReader(d))
+			if err != nil {
+				return nil, status.Errorf(codes.Internal, "grpc: failed to decompress the received message %v", err)
+			}
+			d, err = ioutil.ReadAll(dcReader)
+			if err != nil {
+				return nil, status.Errorf(codes.Internal, "grpc: failed to decompress the received message %v", err)
+			}
+		}
+	}
+	if len(d) > maxReceiveMessageSize {
+		// TODO: Revisit the error code. Currently keep it consistent with java
+		// implementation.
+		return nil, status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max (%d vs. %d)", len(d), maxReceiveMessageSize)
+	}
+	return d, nil
+}
+
+// For the two compressor parameters, both should not be set, but if they are,
+// dc takes precedence over compressor.
+// TODO(dfawley): wrap the old compressor/decompressor using the new API?
+func recv(p *parser, c baseCodec, s *transport.Stream, dc Decompressor, m interface{}, maxReceiveMessageSize int, inPayload *stats.InPayload, compressor encoding.Compressor) error {
+	d, err := recvAndDecompress(p, s, dc, maxReceiveMessageSize, inPayload, compressor)
+	if err != nil {
+		return err
+	}
+	if err := c.Unmarshal(d, m); err != nil {
+		return status.Errorf(codes.Internal, "grpc: failed to unmarshal the received message %v", err)
+	}
+	if inPayload != nil {
+		inPayload.RecvTime = time.Now()
+		inPayload.Payload = m
+		// TODO truncate large payload.
+		inPayload.Data = d
+		inPayload.Length = len(d)
+	}
+	return nil
+}
+
+type rpcInfo struct {
+	failfast bool
+}
+
+type rpcInfoContextKey struct{}
+
+func newContextWithRPCInfo(ctx context.Context, failfast bool) context.Context {
+	return context.WithValue(ctx, rpcInfoContextKey{}, &rpcInfo{failfast: failfast})
+}
+
+func rpcInfoFromContext(ctx context.Context) (s *rpcInfo, ok bool) {
+	s, ok = ctx.Value(rpcInfoContextKey{}).(*rpcInfo)
+	return
+}
+
+// Code returns the error code for err if it was produced by the rpc system.
+// Otherwise, it returns codes.Unknown.
+//
+// Deprecated: use status.FromError and Code method instead.
+func Code(err error) codes.Code {
+	if s, ok := status.FromError(err); ok {
+		return s.Code()
+	}
+	return codes.Unknown
+}
+
+// ErrorDesc returns the error description of err if it was produced by the rpc system.
+// Otherwise, it returns err.Error() or empty string when err is nil.
+//
+// Deprecated: use status.FromError and Message method instead.
+func ErrorDesc(err error) string {
+	if s, ok := status.FromError(err); ok {
+		return s.Message()
+	}
+	return err.Error()
+}
+
+// Errorf returns an error containing an error code and a description;
+// Errorf returns nil if c is OK.
+//
+// Deprecated: use status.Errorf instead.
+func Errorf(c codes.Code, format string, a ...interface{}) error {
+	return status.Errorf(c, format, a...)
+}
+
+// setCallInfoCodec should only be called after CallOptions have been applied.
+func setCallInfoCodec(c *callInfo) error {
+	if c.codec != nil {
+		// codec was already set by a CallOption; use it.
+		return nil
+	}
+
+	if c.contentSubtype == "" {
+		// No codec specified in CallOptions; use proto by default.
+		c.codec = encoding.GetCodec(proto.Name)
+		return nil
+	}
+
+	// c.contentSubtype is already lowercased in CallContentSubtype
+	c.codec = encoding.GetCodec(c.contentSubtype)
+	if c.codec == nil {
+		return status.Errorf(codes.Internal, "no codec registered for content-subtype %s", c.contentSubtype)
+	}
+	return nil
+}
+
+// parseDialTarget returns the network and address to pass to dialer
+func parseDialTarget(target string) (net string, addr string) {
+	net = "tcp"
+
+	m1 := strings.Index(target, ":")
+	m2 := strings.Index(target, ":/")
+
+	// handle unix:addr which will fail with url.Parse
+	if m1 >= 0 && m2 < 0 {
+		if n := target[0:m1]; n == "unix" {
+			net = n
+			addr = target[m1+1:]
+			return net, addr
+		}
+	}
+	if m2 >= 0 {
+		t, err := url.Parse(target)
+		if err != nil {
+			return net, target
+		}
+		scheme := t.Scheme
+		addr = t.Path
+		if scheme == "unix" {
+			net = scheme
+			if addr == "" {
+				addr = t.Host
+			}
+			return net, addr
+		}
+	}
+
+	return net, target
+}
+
+// channelzData is used to store channelz related data for ClientConn, addrConn and Server.
+// These fields cannot be embedded in the original structs (e.g. ClientConn), since to do atomic
+// operation on int64 variable on 32-bit machine, user is responsible to enforce memory alignment.
+// Here, by grouping those int64 fields inside a struct, we are enforcing the alignment.
+type channelzData struct {
+	callsStarted   int64
+	callsFailed    int64
+	callsSucceeded int64
+	// lastCallStartedTime stores the timestamp that last call starts. It is of int64 type instead of
+	// time.Time since it's more costly to atomically update time.Time variable than int64 variable.
+	lastCallStartedTime int64
+}
+
+// The SupportPackageIsVersion variables are referenced from generated protocol
+// buffer files to ensure compatibility with the gRPC version used.  The latest
+// support package version is 5.
+//
+// Older versions are kept for compatibility. They may be removed if
+// compatibility cannot be maintained.
+//
+// These constants should not be referenced from any other code.
+const (
+	SupportPackageIsVersion3 = true
+	SupportPackageIsVersion4 = true
+	SupportPackageIsVersion5 = true
+)
+
+const grpcUA = "grpc-go/" + Version
diff --git a/go/vendor/google.golang.org/grpc/server.go b/go/vendor/google.golang.org/grpc/server.go
new file mode 100644
index 0000000..920da5e
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/server.go
@@ -0,0 +1,1380 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"net"
+	"net/http"
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/trace"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/encoding"
+	"google.golang.org/grpc/encoding/proto"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/tap"
+)
+
+const (
+	defaultServerMaxReceiveMessageSize = 1024 * 1024 * 4
+	defaultServerMaxSendMessageSize    = math.MaxInt32
+)
+
+type methodHandler func(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor UnaryServerInterceptor) (interface{}, error)
+
+// MethodDesc represents an RPC service's method specification.
+type MethodDesc struct {
+	MethodName string
+	Handler    methodHandler
+}
+
+// ServiceDesc represents an RPC service's specification.
+type ServiceDesc struct {
+	ServiceName string
+	// The pointer to the service interface. Used to check whether the user
+	// provided implementation satisfies the interface requirements.
+	HandlerType interface{}
+	Methods     []MethodDesc
+	Streams     []StreamDesc
+	Metadata    interface{}
+}
+
+// service consists of the information of the server serving this service and
+// the methods in this service.
+type service struct {
+	server interface{} // the server for service methods
+	md     map[string]*MethodDesc
+	sd     map[string]*StreamDesc
+	mdata  interface{}
+}
+
+// Server is a gRPC server to serve RPC requests.
+type Server struct {
+	opts options
+
+	mu     sync.Mutex // guards following
+	lis    map[net.Listener]bool
+	conns  map[io.Closer]bool
+	serve  bool
+	drain  bool
+	cv     *sync.Cond          // signaled when connections close for GracefulStop
+	m      map[string]*service // service name -> service info
+	events trace.EventLog
+
+	quit               chan struct{}
+	done               chan struct{}
+	quitOnce           sync.Once
+	doneOnce           sync.Once
+	channelzRemoveOnce sync.Once
+	serveWG            sync.WaitGroup // counts active Serve goroutines for GracefulStop
+
+	channelzID int64 // channelz unique identification number
+	czData     *channelzData
+}
+
+type options struct {
+	creds                 credentials.TransportCredentials
+	codec                 baseCodec
+	cp                    Compressor
+	dc                    Decompressor
+	unaryInt              UnaryServerInterceptor
+	streamInt             StreamServerInterceptor
+	inTapHandle           tap.ServerInHandle
+	statsHandler          stats.Handler
+	maxConcurrentStreams  uint32
+	maxReceiveMessageSize int
+	maxSendMessageSize    int
+	unknownStreamDesc     *StreamDesc
+	keepaliveParams       keepalive.ServerParameters
+	keepalivePolicy       keepalive.EnforcementPolicy
+	initialWindowSize     int32
+	initialConnWindowSize int32
+	writeBufferSize       int
+	readBufferSize        int
+	connectionTimeout     time.Duration
+	maxHeaderListSize     *uint32
+}
+
+var defaultServerOptions = options{
+	maxReceiveMessageSize: defaultServerMaxReceiveMessageSize,
+	maxSendMessageSize:    defaultServerMaxSendMessageSize,
+	connectionTimeout:     120 * time.Second,
+	writeBufferSize:       defaultWriteBufSize,
+	readBufferSize:        defaultReadBufSize,
+}
+
+// A ServerOption sets options such as credentials, codec and keepalive parameters, etc.
+type ServerOption func(*options)
+
+// WriteBufferSize determines how much data can be batched before doing a write on the wire.
+// The corresponding memory allocation for this buffer will be twice the size to keep syscalls low.
+// The default value for this buffer is 32KB.
+// Zero will disable the write buffer such that each write will be on underlying connection.
+// Note: A Send call may not directly translate to a write.
+func WriteBufferSize(s int) ServerOption {
+	return func(o *options) {
+		o.writeBufferSize = s
+	}
+}
+
+// ReadBufferSize lets you set the size of read buffer, this determines how much data can be read at most
+// for one read syscall.
+// The default value for this buffer is 32KB.
+// Zero will disable read buffer for a connection so data framer can access the underlying
+// conn directly.
+func ReadBufferSize(s int) ServerOption {
+	return func(o *options) {
+		o.readBufferSize = s
+	}
+}
+
+// InitialWindowSize returns a ServerOption that sets window size for stream.
+// The lower bound for window size is 64K and any value smaller than that will be ignored.
+func InitialWindowSize(s int32) ServerOption {
+	return func(o *options) {
+		o.initialWindowSize = s
+	}
+}
+
+// InitialConnWindowSize returns a ServerOption that sets window size for a connection.
+// The lower bound for window size is 64K and any value smaller than that will be ignored.
+func InitialConnWindowSize(s int32) ServerOption {
+	return func(o *options) {
+		o.initialConnWindowSize = s
+	}
+}
+
+// KeepaliveParams returns a ServerOption that sets keepalive and max-age parameters for the server.
+func KeepaliveParams(kp keepalive.ServerParameters) ServerOption {
+	return func(o *options) {
+		o.keepaliveParams = kp
+	}
+}
+
+// KeepaliveEnforcementPolicy returns a ServerOption that sets keepalive enforcement policy for the server.
+func KeepaliveEnforcementPolicy(kep keepalive.EnforcementPolicy) ServerOption {
+	return func(o *options) {
+		o.keepalivePolicy = kep
+	}
+}
+
+// CustomCodec returns a ServerOption that sets a codec for message marshaling and unmarshaling.
+//
+// This will override any lookups by content-subtype for Codecs registered with RegisterCodec.
+func CustomCodec(codec Codec) ServerOption {
+	return func(o *options) {
+		o.codec = codec
+	}
+}
+
+// RPCCompressor returns a ServerOption that sets a compressor for outbound
+// messages.  For backward compatibility, all outbound messages will be sent
+// using this compressor, regardless of incoming message compression.  By
+// default, server messages will be sent using the same compressor with which
+// request messages were sent.
+//
+// Deprecated: use encoding.RegisterCompressor instead.
+func RPCCompressor(cp Compressor) ServerOption {
+	return func(o *options) {
+		o.cp = cp
+	}
+}
+
+// RPCDecompressor returns a ServerOption that sets a decompressor for inbound
+// messages.  It has higher priority than decompressors registered via
+// encoding.RegisterCompressor.
+//
+// Deprecated: use encoding.RegisterCompressor instead.
+func RPCDecompressor(dc Decompressor) ServerOption {
+	return func(o *options) {
+		o.dc = dc
+	}
+}
+
+// MaxMsgSize returns a ServerOption to set the max message size in bytes the server can receive.
+// If this is not set, gRPC uses the default limit.
+//
+// Deprecated: use MaxRecvMsgSize instead.
+func MaxMsgSize(m int) ServerOption {
+	return MaxRecvMsgSize(m)
+}
+
+// MaxRecvMsgSize returns a ServerOption to set the max message size in bytes the server can receive.
+// If this is not set, gRPC uses the default 4MB.
+func MaxRecvMsgSize(m int) ServerOption {
+	return func(o *options) {
+		o.maxReceiveMessageSize = m
+	}
+}
+
+// MaxSendMsgSize returns a ServerOption to set the max message size in bytes the server can send.
+// If this is not set, gRPC uses the default 4MB.
+func MaxSendMsgSize(m int) ServerOption {
+	return func(o *options) {
+		o.maxSendMessageSize = m
+	}
+}
+
+// MaxConcurrentStreams returns a ServerOption that will apply a limit on the number
+// of concurrent streams to each ServerTransport.
+func MaxConcurrentStreams(n uint32) ServerOption {
+	return func(o *options) {
+		o.maxConcurrentStreams = n
+	}
+}
+
+// Creds returns a ServerOption that sets credentials for server connections.
+func Creds(c credentials.TransportCredentials) ServerOption {
+	return func(o *options) {
+		o.creds = c
+	}
+}
+
+// UnaryInterceptor returns a ServerOption that sets the UnaryServerInterceptor for the
+// server. Only one unary interceptor can be installed. The construction of multiple
+// interceptors (e.g., chaining) can be implemented at the caller.
+func UnaryInterceptor(i UnaryServerInterceptor) ServerOption {
+	return func(o *options) {
+		if o.unaryInt != nil {
+			panic("The unary server interceptor was already set and may not be reset.")
+		}
+		o.unaryInt = i
+	}
+}
+
+// StreamInterceptor returns a ServerOption that sets the StreamServerInterceptor for the
+// server. Only one stream interceptor can be installed.
+func StreamInterceptor(i StreamServerInterceptor) ServerOption {
+	return func(o *options) {
+		if o.streamInt != nil {
+			panic("The stream server interceptor was already set and may not be reset.")
+		}
+		o.streamInt = i
+	}
+}
+
+// InTapHandle returns a ServerOption that sets the tap handle for all the server
+// transport to be created. Only one can be installed.
+func InTapHandle(h tap.ServerInHandle) ServerOption {
+	return func(o *options) {
+		if o.inTapHandle != nil {
+			panic("The tap handle was already set and may not be reset.")
+		}
+		o.inTapHandle = h
+	}
+}
+
+// StatsHandler returns a ServerOption that sets the stats handler for the server.
+func StatsHandler(h stats.Handler) ServerOption {
+	return func(o *options) {
+		o.statsHandler = h
+	}
+}
+
+// UnknownServiceHandler returns a ServerOption that allows for adding a custom
+// unknown service handler. The provided method is a bidi-streaming RPC service
+// handler that will be invoked instead of returning the "unimplemented" gRPC
+// error whenever a request is received for an unregistered service or method.
+// The handling function has full access to the Context of the request and the
+// stream, and the invocation bypasses interceptors.
+func UnknownServiceHandler(streamHandler StreamHandler) ServerOption {
+	return func(o *options) {
+		o.unknownStreamDesc = &StreamDesc{
+			StreamName: "unknown_service_handler",
+			Handler:    streamHandler,
+			// We need to assume that the users of the streamHandler will want to use both.
+			ClientStreams: true,
+			ServerStreams: true,
+		}
+	}
+}
+
+// ConnectionTimeout returns a ServerOption that sets the timeout for
+// connection establishment (up to and including HTTP/2 handshaking) for all
+// new connections.  If this is not set, the default is 120 seconds.  A zero or
+// negative value will result in an immediate timeout.
+//
+// This API is EXPERIMENTAL.
+func ConnectionTimeout(d time.Duration) ServerOption {
+	return func(o *options) {
+		o.connectionTimeout = d
+	}
+}
+
+// MaxHeaderListSize returns a ServerOption that sets the max (uncompressed) size
+// of header list that the server is prepared to accept.
+func MaxHeaderListSize(s uint32) ServerOption {
+	return func(o *options) {
+		o.maxHeaderListSize = &s
+	}
+}
+
+// NewServer creates a gRPC server which has no service registered and has not
+// started to accept requests yet.
+func NewServer(opt ...ServerOption) *Server {
+	opts := defaultServerOptions
+	for _, o := range opt {
+		o(&opts)
+	}
+	s := &Server{
+		lis:    make(map[net.Listener]bool),
+		opts:   opts,
+		conns:  make(map[io.Closer]bool),
+		m:      make(map[string]*service),
+		quit:   make(chan struct{}),
+		done:   make(chan struct{}),
+		czData: new(channelzData),
+	}
+	s.cv = sync.NewCond(&s.mu)
+	if EnableTracing {
+		_, file, line, _ := runtime.Caller(1)
+		s.events = trace.NewEventLog("grpc.Server", fmt.Sprintf("%s:%d", file, line))
+	}
+
+	if channelz.IsOn() {
+		s.channelzID = channelz.RegisterServer(&channelzServer{s}, "")
+	}
+	return s
+}
+
+// printf records an event in s's event log, unless s has been stopped.
+// REQUIRES s.mu is held.
+func (s *Server) printf(format string, a ...interface{}) {
+	if s.events != nil {
+		s.events.Printf(format, a...)
+	}
+}
+
+// errorf records an error in s's event log, unless s has been stopped.
+// REQUIRES s.mu is held.
+func (s *Server) errorf(format string, a ...interface{}) {
+	if s.events != nil {
+		s.events.Errorf(format, a...)
+	}
+}
+
+// RegisterService registers a service and its implementation to the gRPC
+// server. It is called from the IDL generated code. This must be called before
+// invoking Serve.
+func (s *Server) RegisterService(sd *ServiceDesc, ss interface{}) {
+	ht := reflect.TypeOf(sd.HandlerType).Elem()
+	st := reflect.TypeOf(ss)
+	if !st.Implements(ht) {
+		grpclog.Fatalf("grpc: Server.RegisterService found the handler of type %v that does not satisfy %v", st, ht)
+	}
+	s.register(sd, ss)
+}
+
+func (s *Server) register(sd *ServiceDesc, ss interface{}) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.printf("RegisterService(%q)", sd.ServiceName)
+	if s.serve {
+		grpclog.Fatalf("grpc: Server.RegisterService after Server.Serve for %q", sd.ServiceName)
+	}
+	if _, ok := s.m[sd.ServiceName]; ok {
+		grpclog.Fatalf("grpc: Server.RegisterService found duplicate service registration for %q", sd.ServiceName)
+	}
+	srv := &service{
+		server: ss,
+		md:     make(map[string]*MethodDesc),
+		sd:     make(map[string]*StreamDesc),
+		mdata:  sd.Metadata,
+	}
+	for i := range sd.Methods {
+		d := &sd.Methods[i]
+		srv.md[d.MethodName] = d
+	}
+	for i := range sd.Streams {
+		d := &sd.Streams[i]
+		srv.sd[d.StreamName] = d
+	}
+	s.m[sd.ServiceName] = srv
+}
+
+// MethodInfo contains the information of an RPC including its method name and type.
+type MethodInfo struct {
+	// Name is the method name only, without the service name or package name.
+	Name string
+	// IsClientStream indicates whether the RPC is a client streaming RPC.
+	IsClientStream bool
+	// IsServerStream indicates whether the RPC is a server streaming RPC.
+	IsServerStream bool
+}
+
+// ServiceInfo contains unary RPC method info, streaming RPC method info and metadata for a service.
+type ServiceInfo struct {
+	Methods []MethodInfo
+	// Metadata is the metadata specified in ServiceDesc when registering service.
+	Metadata interface{}
+}
+
+// GetServiceInfo returns a map from service names to ServiceInfo.
+// Service names include the package names, in the form of <package>.<service>.
+func (s *Server) GetServiceInfo() map[string]ServiceInfo {
+	ret := make(map[string]ServiceInfo)
+	for n, srv := range s.m {
+		methods := make([]MethodInfo, 0, len(srv.md)+len(srv.sd))
+		for m := range srv.md {
+			methods = append(methods, MethodInfo{
+				Name:           m,
+				IsClientStream: false,
+				IsServerStream: false,
+			})
+		}
+		for m, d := range srv.sd {
+			methods = append(methods, MethodInfo{
+				Name:           m,
+				IsClientStream: d.ClientStreams,
+				IsServerStream: d.ServerStreams,
+			})
+		}
+
+		ret[n] = ServiceInfo{
+			Methods:  methods,
+			Metadata: srv.mdata,
+		}
+	}
+	return ret
+}
+
+// ErrServerStopped indicates that the operation is now illegal because of
+// the server being stopped.
+var ErrServerStopped = errors.New("grpc: the server has been stopped")
+
+func (s *Server) useTransportAuthenticator(rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
+	if s.opts.creds == nil {
+		return rawConn, nil, nil
+	}
+	return s.opts.creds.ServerHandshake(rawConn)
+}
+
+type listenSocket struct {
+	net.Listener
+	channelzID int64
+}
+
+func (l *listenSocket) ChannelzMetric() *channelz.SocketInternalMetric {
+	return &channelz.SocketInternalMetric{
+		SocketOptions: channelz.GetSocketOption(l.Listener),
+		LocalAddr:     l.Listener.Addr(),
+	}
+}
+
+func (l *listenSocket) Close() error {
+	err := l.Listener.Close()
+	if channelz.IsOn() {
+		channelz.RemoveEntry(l.channelzID)
+	}
+	return err
+}
+
+// Serve accepts incoming connections on the listener lis, creating a new
+// ServerTransport and service goroutine for each. The service goroutines
+// read gRPC requests and then call the registered handlers to reply to them.
+// Serve returns when lis.Accept fails with fatal errors.  lis will be closed when
+// this method returns.
+// Serve will return a non-nil error unless Stop or GracefulStop is called.
+func (s *Server) Serve(lis net.Listener) error {
+	s.mu.Lock()
+	s.printf("serving")
+	s.serve = true
+	if s.lis == nil {
+		// Serve called after Stop or GracefulStop.
+		s.mu.Unlock()
+		lis.Close()
+		return ErrServerStopped
+	}
+
+	s.serveWG.Add(1)
+	defer func() {
+		s.serveWG.Done()
+		select {
+		// Stop or GracefulStop called; block until done and return nil.
+		case <-s.quit:
+			<-s.done
+		default:
+		}
+	}()
+
+	ls := &listenSocket{Listener: lis}
+	s.lis[ls] = true
+
+	if channelz.IsOn() {
+		ls.channelzID = channelz.RegisterListenSocket(ls, s.channelzID, "")
+	}
+	s.mu.Unlock()
+
+	defer func() {
+		s.mu.Lock()
+		if s.lis != nil && s.lis[ls] {
+			ls.Close()
+			delete(s.lis, ls)
+		}
+		s.mu.Unlock()
+	}()
+
+	var tempDelay time.Duration // how long to sleep on accept failure
+
+	for {
+		rawConn, err := lis.Accept()
+		if err != nil {
+			if ne, ok := err.(interface {
+				Temporary() bool
+			}); ok && ne.Temporary() {
+				if tempDelay == 0 {
+					tempDelay = 5 * time.Millisecond
+				} else {
+					tempDelay *= 2
+				}
+				if max := 1 * time.Second; tempDelay > max {
+					tempDelay = max
+				}
+				s.mu.Lock()
+				s.printf("Accept error: %v; retrying in %v", err, tempDelay)
+				s.mu.Unlock()
+				timer := time.NewTimer(tempDelay)
+				select {
+				case <-timer.C:
+				case <-s.quit:
+					timer.Stop()
+					return nil
+				}
+				continue
+			}
+			s.mu.Lock()
+			s.printf("done serving; Accept = %v", err)
+			s.mu.Unlock()
+
+			select {
+			case <-s.quit:
+				return nil
+			default:
+			}
+			return err
+		}
+		tempDelay = 0
+		// Start a new goroutine to deal with rawConn so we don't stall this Accept
+		// loop goroutine.
+		//
+		// Make sure we account for the goroutine so GracefulStop doesn't nil out
+		// s.conns before this conn can be added.
+		s.serveWG.Add(1)
+		go func() {
+			s.handleRawConn(rawConn)
+			s.serveWG.Done()
+		}()
+	}
+}
+
+// handleRawConn forks a goroutine to handle a just-accepted connection that
+// has not had any I/O performed on it yet.
+func (s *Server) handleRawConn(rawConn net.Conn) {
+	rawConn.SetDeadline(time.Now().Add(s.opts.connectionTimeout))
+	conn, authInfo, err := s.useTransportAuthenticator(rawConn)
+	if err != nil {
+		s.mu.Lock()
+		s.errorf("ServerHandshake(%q) failed: %v", rawConn.RemoteAddr(), err)
+		s.mu.Unlock()
+		grpclog.Warningf("grpc: Server.Serve failed to complete security handshake from %q: %v", rawConn.RemoteAddr(), err)
+		// If serverHandshake returns ErrConnDispatched, keep rawConn open.
+		if err != credentials.ErrConnDispatched {
+			rawConn.Close()
+		}
+		rawConn.SetDeadline(time.Time{})
+		return
+	}
+
+	s.mu.Lock()
+	if s.conns == nil {
+		s.mu.Unlock()
+		conn.Close()
+		return
+	}
+	s.mu.Unlock()
+
+	// Finish handshaking (HTTP2)
+	st := s.newHTTP2Transport(conn, authInfo)
+	if st == nil {
+		return
+	}
+
+	rawConn.SetDeadline(time.Time{})
+	if !s.addConn(st) {
+		return
+	}
+	go func() {
+		s.serveStreams(st)
+		s.removeConn(st)
+	}()
+}
+
+// newHTTP2Transport sets up a http/2 transport (using the
+// gRPC http2 server transport in transport/http2_server.go).
+func (s *Server) newHTTP2Transport(c net.Conn, authInfo credentials.AuthInfo) transport.ServerTransport {
+	config := &transport.ServerConfig{
+		MaxStreams:            s.opts.maxConcurrentStreams,
+		AuthInfo:              authInfo,
+		InTapHandle:           s.opts.inTapHandle,
+		StatsHandler:          s.opts.statsHandler,
+		KeepaliveParams:       s.opts.keepaliveParams,
+		KeepalivePolicy:       s.opts.keepalivePolicy,
+		InitialWindowSize:     s.opts.initialWindowSize,
+		InitialConnWindowSize: s.opts.initialConnWindowSize,
+		WriteBufferSize:       s.opts.writeBufferSize,
+		ReadBufferSize:        s.opts.readBufferSize,
+		ChannelzParentID:      s.channelzID,
+		MaxHeaderListSize:     s.opts.maxHeaderListSize,
+	}
+	st, err := transport.NewServerTransport("http2", c, config)
+	if err != nil {
+		s.mu.Lock()
+		s.errorf("NewServerTransport(%q) failed: %v", c.RemoteAddr(), err)
+		s.mu.Unlock()
+		c.Close()
+		grpclog.Warningln("grpc: Server.Serve failed to create ServerTransport: ", err)
+		return nil
+	}
+
+	return st
+}
+
+func (s *Server) serveStreams(st transport.ServerTransport) {
+	defer st.Close()
+	var wg sync.WaitGroup
+	st.HandleStreams(func(stream *transport.Stream) {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			s.handleStream(st, stream, s.traceInfo(st, stream))
+		}()
+	}, func(ctx context.Context, method string) context.Context {
+		if !EnableTracing {
+			return ctx
+		}
+		tr := trace.New("grpc.Recv."+methodFamily(method), method)
+		return trace.NewContext(ctx, tr)
+	})
+	wg.Wait()
+}
+
+var _ http.Handler = (*Server)(nil)
+
+// ServeHTTP implements the Go standard library's http.Handler
+// interface by responding to the gRPC request r, by looking up
+// the requested gRPC method in the gRPC server s.
+//
+// The provided HTTP request must have arrived on an HTTP/2
+// connection. When using the Go standard library's server,
+// practically this means that the Request must also have arrived
+// over TLS.
+//
+// To share one port (such as 443 for https) between gRPC and an
+// existing http.Handler, use a root http.Handler such as:
+//
+//   if r.ProtoMajor == 2 && strings.HasPrefix(
+//   	r.Header.Get("Content-Type"), "application/grpc") {
+//   	grpcServer.ServeHTTP(w, r)
+//   } else {
+//   	yourMux.ServeHTTP(w, r)
+//   }
+//
+// Note that ServeHTTP uses Go's HTTP/2 server implementation which is totally
+// separate from grpc-go's HTTP/2 server. Performance and features may vary
+// between the two paths. ServeHTTP does not support some gRPC features
+// available through grpc-go's HTTP/2 server, and it is currently EXPERIMENTAL
+// and subject to change.
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	st, err := transport.NewServerHandlerTransport(w, r, s.opts.statsHandler)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	if !s.addConn(st) {
+		return
+	}
+	defer s.removeConn(st)
+	s.serveStreams(st)
+}
+
+// traceInfo returns a traceInfo and associates it with stream, if tracing is enabled.
+// If tracing is not enabled, it returns nil.
+func (s *Server) traceInfo(st transport.ServerTransport, stream *transport.Stream) (trInfo *traceInfo) {
+	tr, ok := trace.FromContext(stream.Context())
+	if !ok {
+		return nil
+	}
+
+	trInfo = &traceInfo{
+		tr: tr,
+	}
+	trInfo.firstLine.client = false
+	trInfo.firstLine.remoteAddr = st.RemoteAddr()
+
+	if dl, ok := stream.Context().Deadline(); ok {
+		trInfo.firstLine.deadline = dl.Sub(time.Now())
+	}
+	return trInfo
+}
+
+func (s *Server) addConn(c io.Closer) bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.conns == nil {
+		c.Close()
+		return false
+	}
+	if s.drain {
+		// Transport added after we drained our existing conns: drain it
+		// immediately.
+		c.(transport.ServerTransport).Drain()
+	}
+	s.conns[c] = true
+	return true
+}
+
+func (s *Server) removeConn(c io.Closer) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.conns != nil {
+		delete(s.conns, c)
+		s.cv.Broadcast()
+	}
+}
+
+func (s *Server) channelzMetric() *channelz.ServerInternalMetric {
+	return &channelz.ServerInternalMetric{
+		CallsStarted:             atomic.LoadInt64(&s.czData.callsStarted),
+		CallsSucceeded:           atomic.LoadInt64(&s.czData.callsSucceeded),
+		CallsFailed:              atomic.LoadInt64(&s.czData.callsFailed),
+		LastCallStartedTimestamp: time.Unix(0, atomic.LoadInt64(&s.czData.lastCallStartedTime)),
+	}
+}
+
+func (s *Server) incrCallsStarted() {
+	atomic.AddInt64(&s.czData.callsStarted, 1)
+	atomic.StoreInt64(&s.czData.lastCallStartedTime, time.Now().UnixNano())
+}
+
+func (s *Server) incrCallsSucceeded() {
+	atomic.AddInt64(&s.czData.callsSucceeded, 1)
+}
+
+func (s *Server) incrCallsFailed() {
+	atomic.AddInt64(&s.czData.callsFailed, 1)
+}
+
+func (s *Server) sendResponse(t transport.ServerTransport, stream *transport.Stream, msg interface{}, cp Compressor, opts *transport.Options, comp encoding.Compressor) error {
+	data, err := encode(s.getCodec(stream.ContentSubtype()), msg)
+	if err != nil {
+		grpclog.Errorln("grpc: server failed to encode response: ", err)
+		return err
+	}
+	compData, err := compress(data, cp, comp)
+	if err != nil {
+		grpclog.Errorln("grpc: server failed to compress response: ", err)
+		return err
+	}
+	hdr, payload := msgHeader(data, compData)
+	// TODO(dfawley): should we be checking len(data) instead?
+	if len(payload) > s.opts.maxSendMessageSize {
+		return status.Errorf(codes.ResourceExhausted, "grpc: trying to send message larger than max (%d vs. %d)", len(payload), s.opts.maxSendMessageSize)
+	}
+	err = t.Write(stream, hdr, payload, opts)
+	if err == nil && s.opts.statsHandler != nil {
+		s.opts.statsHandler.HandleRPC(stream.Context(), outPayload(false, msg, data, payload, time.Now()))
+	}
+	return err
+}
+
+func (s *Server) processUnaryRPC(t transport.ServerTransport, stream *transport.Stream, srv *service, md *MethodDesc, trInfo *traceInfo) (err error) {
+	if channelz.IsOn() {
+		s.incrCallsStarted()
+		defer func() {
+			if err != nil && err != io.EOF {
+				s.incrCallsFailed()
+			} else {
+				s.incrCallsSucceeded()
+			}
+		}()
+	}
+	sh := s.opts.statsHandler
+	if sh != nil {
+		beginTime := time.Now()
+		begin := &stats.Begin{
+			BeginTime: beginTime,
+		}
+		sh.HandleRPC(stream.Context(), begin)
+		defer func() {
+			end := &stats.End{
+				BeginTime: beginTime,
+				EndTime:   time.Now(),
+			}
+			if err != nil && err != io.EOF {
+				end.Error = toRPCErr(err)
+			}
+			sh.HandleRPC(stream.Context(), end)
+		}()
+	}
+	if trInfo != nil {
+		defer trInfo.tr.Finish()
+		trInfo.firstLine.client = false
+		trInfo.tr.LazyLog(&trInfo.firstLine, false)
+		defer func() {
+			if err != nil && err != io.EOF {
+				trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+				trInfo.tr.SetError()
+			}
+		}()
+	}
+
+	// comp and cp are used for compression.  decomp and dc are used for
+	// decompression.  If comp and decomp are both set, they are the same;
+	// however they are kept separate to ensure that at most one of the
+	// compressor/decompressor variable pairs are set for use later.
+	var comp, decomp encoding.Compressor
+	var cp Compressor
+	var dc Decompressor
+
+	// If dc is set and matches the stream's compression, use it.  Otherwise, try
+	// to find a matching registered compressor for decomp.
+	if rc := stream.RecvCompress(); s.opts.dc != nil && s.opts.dc.Type() == rc {
+		dc = s.opts.dc
+	} else if rc != "" && rc != encoding.Identity {
+		decomp = encoding.GetCompressor(rc)
+		if decomp == nil {
+			st := status.Newf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", rc)
+			t.WriteStatus(stream, st)
+			return st.Err()
+		}
+	}
+
+	// If cp is set, use it.  Otherwise, attempt to compress the response using
+	// the incoming message compression method.
+	//
+	// NOTE: this needs to be ahead of all handling, https://github.com/grpc/grpc-go/issues/686.
+	if s.opts.cp != nil {
+		cp = s.opts.cp
+		stream.SetSendCompress(cp.Type())
+	} else if rc := stream.RecvCompress(); rc != "" && rc != encoding.Identity {
+		// Legacy compressor not specified; attempt to respond with same encoding.
+		comp = encoding.GetCompressor(rc)
+		if comp != nil {
+			stream.SetSendCompress(rc)
+		}
+	}
+
+	var inPayload *stats.InPayload
+	if sh != nil {
+		inPayload = &stats.InPayload{
+			RecvTime: time.Now(),
+		}
+	}
+	d, err := recvAndDecompress(&parser{r: stream}, stream, dc, s.opts.maxReceiveMessageSize, inPayload, decomp)
+	if err != nil {
+		if st, ok := status.FromError(err); ok {
+			if e := t.WriteStatus(stream, st); e != nil {
+				grpclog.Warningf("grpc: Server.processUnaryRPC failed to write status %v", e)
+			}
+		}
+		return err
+	}
+	if channelz.IsOn() {
+		t.IncrMsgRecv()
+	}
+	df := func(v interface{}) error {
+		if err := s.getCodec(stream.ContentSubtype()).Unmarshal(d, v); err != nil {
+			return status.Errorf(codes.Internal, "grpc: error unmarshalling request: %v", err)
+		}
+		if inPayload != nil {
+			inPayload.Payload = v
+			inPayload.Data = d
+			inPayload.Length = len(d)
+			sh.HandleRPC(stream.Context(), inPayload)
+		}
+		if trInfo != nil {
+			trInfo.tr.LazyLog(&payload{sent: false, msg: v}, true)
+		}
+		return nil
+	}
+	ctx := NewContextWithServerTransportStream(stream.Context(), stream)
+	reply, appErr := md.Handler(srv.server, ctx, df, s.opts.unaryInt)
+	if appErr != nil {
+		appStatus, ok := status.FromError(appErr)
+		if !ok {
+			// Convert appErr if it is not a grpc status error.
+			appErr = status.Error(codes.Unknown, appErr.Error())
+			appStatus, _ = status.FromError(appErr)
+		}
+		if trInfo != nil {
+			trInfo.tr.LazyLog(stringer(appStatus.Message()), true)
+			trInfo.tr.SetError()
+		}
+		if e := t.WriteStatus(stream, appStatus); e != nil {
+			grpclog.Warningf("grpc: Server.processUnaryRPC failed to write status: %v", e)
+		}
+		return appErr
+	}
+	if trInfo != nil {
+		trInfo.tr.LazyLog(stringer("OK"), false)
+	}
+	opts := &transport.Options{Last: true}
+
+	if err := s.sendResponse(t, stream, reply, cp, opts, comp); err != nil {
+		if err == io.EOF {
+			// The entire stream is done (for unary RPC only).
+			return err
+		}
+		if s, ok := status.FromError(err); ok {
+			if e := t.WriteStatus(stream, s); e != nil {
+				grpclog.Warningf("grpc: Server.processUnaryRPC failed to write status: %v", e)
+			}
+		} else {
+			switch st := err.(type) {
+			case transport.ConnectionError:
+				// Nothing to do here.
+			default:
+				panic(fmt.Sprintf("grpc: Unexpected error (%T) from sendResponse: %v", st, st))
+			}
+		}
+		return err
+	}
+	if channelz.IsOn() {
+		t.IncrMsgSent()
+	}
+	if trInfo != nil {
+		trInfo.tr.LazyLog(&payload{sent: true, msg: reply}, true)
+	}
+	// TODO: Should we be logging if writing status failed here, like above?
+	// Should the logging be in WriteStatus?  Should we ignore the WriteStatus
+	// error or allow the stats handler to see it?
+	return t.WriteStatus(stream, status.New(codes.OK, ""))
+}
+
+func (s *Server) processStreamingRPC(t transport.ServerTransport, stream *transport.Stream, srv *service, sd *StreamDesc, trInfo *traceInfo) (err error) {
+	if channelz.IsOn() {
+		s.incrCallsStarted()
+		defer func() {
+			if err != nil && err != io.EOF {
+				s.incrCallsFailed()
+			} else {
+				s.incrCallsSucceeded()
+			}
+		}()
+	}
+	sh := s.opts.statsHandler
+	if sh != nil {
+		beginTime := time.Now()
+		begin := &stats.Begin{
+			BeginTime: beginTime,
+		}
+		sh.HandleRPC(stream.Context(), begin)
+		defer func() {
+			end := &stats.End{
+				BeginTime: beginTime,
+				EndTime:   time.Now(),
+			}
+			if err != nil && err != io.EOF {
+				end.Error = toRPCErr(err)
+			}
+			sh.HandleRPC(stream.Context(), end)
+		}()
+	}
+	ctx := NewContextWithServerTransportStream(stream.Context(), stream)
+	ss := &serverStream{
+		ctx:                   ctx,
+		t:                     t,
+		s:                     stream,
+		p:                     &parser{r: stream},
+		codec:                 s.getCodec(stream.ContentSubtype()),
+		maxReceiveMessageSize: s.opts.maxReceiveMessageSize,
+		maxSendMessageSize:    s.opts.maxSendMessageSize,
+		trInfo:                trInfo,
+		statsHandler:          sh,
+	}
+
+	// If dc is set and matches the stream's compression, use it.  Otherwise, try
+	// to find a matching registered compressor for decomp.
+	if rc := stream.RecvCompress(); s.opts.dc != nil && s.opts.dc.Type() == rc {
+		ss.dc = s.opts.dc
+	} else if rc != "" && rc != encoding.Identity {
+		ss.decomp = encoding.GetCompressor(rc)
+		if ss.decomp == nil {
+			st := status.Newf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", rc)
+			t.WriteStatus(ss.s, st)
+			return st.Err()
+		}
+	}
+
+	// If cp is set, use it.  Otherwise, attempt to compress the response using
+	// the incoming message compression method.
+	//
+	// NOTE: this needs to be ahead of all handling, https://github.com/grpc/grpc-go/issues/686.
+	if s.opts.cp != nil {
+		ss.cp = s.opts.cp
+		stream.SetSendCompress(s.opts.cp.Type())
+	} else if rc := stream.RecvCompress(); rc != "" && rc != encoding.Identity {
+		// Legacy compressor not specified; attempt to respond with same encoding.
+		ss.comp = encoding.GetCompressor(rc)
+		if ss.comp != nil {
+			stream.SetSendCompress(rc)
+		}
+	}
+
+	if trInfo != nil {
+		trInfo.tr.LazyLog(&trInfo.firstLine, false)
+		defer func() {
+			ss.mu.Lock()
+			if err != nil && err != io.EOF {
+				ss.trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+				ss.trInfo.tr.SetError()
+			}
+			ss.trInfo.tr.Finish()
+			ss.trInfo.tr = nil
+			ss.mu.Unlock()
+		}()
+	}
+	var appErr error
+	var server interface{}
+	if srv != nil {
+		server = srv.server
+	}
+	if s.opts.streamInt == nil {
+		appErr = sd.Handler(server, ss)
+	} else {
+		info := &StreamServerInfo{
+			FullMethod:     stream.Method(),
+			IsClientStream: sd.ClientStreams,
+			IsServerStream: sd.ServerStreams,
+		}
+		appErr = s.opts.streamInt(server, ss, info, sd.Handler)
+	}
+	if appErr != nil {
+		appStatus, ok := status.FromError(appErr)
+		if !ok {
+			appStatus = status.New(codes.Unknown, appErr.Error())
+			appErr = appStatus.Err()
+		}
+		if trInfo != nil {
+			ss.mu.Lock()
+			ss.trInfo.tr.LazyLog(stringer(appStatus.Message()), true)
+			ss.trInfo.tr.SetError()
+			ss.mu.Unlock()
+		}
+		t.WriteStatus(ss.s, appStatus)
+		// TODO: Should we log an error from WriteStatus here and below?
+		return appErr
+	}
+	if trInfo != nil {
+		ss.mu.Lock()
+		ss.trInfo.tr.LazyLog(stringer("OK"), false)
+		ss.mu.Unlock()
+	}
+	return t.WriteStatus(ss.s, status.New(codes.OK, ""))
+}
+
+func (s *Server) handleStream(t transport.ServerTransport, stream *transport.Stream, trInfo *traceInfo) {
+	sm := stream.Method()
+	if sm != "" && sm[0] == '/' {
+		sm = sm[1:]
+	}
+	pos := strings.LastIndex(sm, "/")
+	if pos == -1 {
+		if trInfo != nil {
+			trInfo.tr.LazyLog(&fmtStringer{"Malformed method name %q", []interface{}{sm}}, true)
+			trInfo.tr.SetError()
+		}
+		errDesc := fmt.Sprintf("malformed method name: %q", stream.Method())
+		if err := t.WriteStatus(stream, status.New(codes.ResourceExhausted, errDesc)); err != nil {
+			if trInfo != nil {
+				trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+				trInfo.tr.SetError()
+			}
+			grpclog.Warningf("grpc: Server.handleStream failed to write status: %v", err)
+		}
+		if trInfo != nil {
+			trInfo.tr.Finish()
+		}
+		return
+	}
+	service := sm[:pos]
+	method := sm[pos+1:]
+
+	if srv, ok := s.m[service]; ok {
+		if md, ok := srv.md[method]; ok {
+			s.processUnaryRPC(t, stream, srv, md, trInfo)
+			return
+		}
+		if sd, ok := srv.sd[method]; ok {
+			s.processStreamingRPC(t, stream, srv, sd, trInfo)
+			return
+		}
+	}
+	// Unknown service, or known server unknown method.
+	if unknownDesc := s.opts.unknownStreamDesc; unknownDesc != nil {
+		s.processStreamingRPC(t, stream, nil, unknownDesc, trInfo)
+		return
+	}
+	if trInfo != nil {
+		trInfo.tr.LazyLog(&fmtStringer{"Unknown service %v", []interface{}{service}}, true)
+		trInfo.tr.SetError()
+	}
+	errDesc := fmt.Sprintf("unknown service %v", service)
+	if err := t.WriteStatus(stream, status.New(codes.Unimplemented, errDesc)); err != nil {
+		if trInfo != nil {
+			trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+			trInfo.tr.SetError()
+		}
+		grpclog.Warningf("grpc: Server.handleStream failed to write status: %v", err)
+	}
+	if trInfo != nil {
+		trInfo.tr.Finish()
+	}
+}
+
+// The key to save ServerTransportStream in the context.
+type streamKey struct{}
+
+// NewContextWithServerTransportStream creates a new context from ctx and
+// attaches stream to it.
+//
+// This API is EXPERIMENTAL.
+func NewContextWithServerTransportStream(ctx context.Context, stream ServerTransportStream) context.Context {
+	return context.WithValue(ctx, streamKey{}, stream)
+}
+
+// ServerTransportStream is a minimal interface that a transport stream must
+// implement. This can be used to mock an actual transport stream for tests of
+// handler code that use, for example, grpc.SetHeader (which requires some
+// stream to be in context).
+//
+// See also NewContextWithServerTransportStream.
+//
+// This API is EXPERIMENTAL.
+type ServerTransportStream interface {
+	Method() string
+	SetHeader(md metadata.MD) error
+	SendHeader(md metadata.MD) error
+	SetTrailer(md metadata.MD) error
+}
+
+// ServerTransportStreamFromContext returns the ServerTransportStream saved in
+// ctx. Returns nil if the given context has no stream associated with it
+// (which implies it is not an RPC invocation context).
+//
+// This API is EXPERIMENTAL.
+func ServerTransportStreamFromContext(ctx context.Context) ServerTransportStream {
+	s, _ := ctx.Value(streamKey{}).(ServerTransportStream)
+	return s
+}
+
+// Stop stops the gRPC server. It immediately closes all open
+// connections and listeners.
+// It cancels all active RPCs on the server side and the corresponding
+// pending RPCs on the client side will get notified by connection
+// errors.
+func (s *Server) Stop() {
+	s.quitOnce.Do(func() {
+		close(s.quit)
+	})
+
+	defer func() {
+		s.serveWG.Wait()
+		s.doneOnce.Do(func() {
+			close(s.done)
+		})
+	}()
+
+	s.channelzRemoveOnce.Do(func() {
+		if channelz.IsOn() {
+			channelz.RemoveEntry(s.channelzID)
+		}
+	})
+
+	s.mu.Lock()
+	listeners := s.lis
+	s.lis = nil
+	st := s.conns
+	s.conns = nil
+	// interrupt GracefulStop if Stop and GracefulStop are called concurrently.
+	s.cv.Broadcast()
+	s.mu.Unlock()
+
+	for lis := range listeners {
+		lis.Close()
+	}
+	for c := range st {
+		c.Close()
+	}
+
+	s.mu.Lock()
+	if s.events != nil {
+		s.events.Finish()
+		s.events = nil
+	}
+	s.mu.Unlock()
+}
+
+// GracefulStop stops the gRPC server gracefully. It stops the server from
+// accepting new connections and RPCs and blocks until all the pending RPCs are
+// finished.
+func (s *Server) GracefulStop() {
+	s.quitOnce.Do(func() {
+		close(s.quit)
+	})
+
+	defer func() {
+		s.doneOnce.Do(func() {
+			close(s.done)
+		})
+	}()
+
+	s.channelzRemoveOnce.Do(func() {
+		if channelz.IsOn() {
+			channelz.RemoveEntry(s.channelzID)
+		}
+	})
+	s.mu.Lock()
+	if s.conns == nil {
+		s.mu.Unlock()
+		return
+	}
+
+	for lis := range s.lis {
+		lis.Close()
+	}
+	s.lis = nil
+	if !s.drain {
+		for c := range s.conns {
+			c.(transport.ServerTransport).Drain()
+		}
+		s.drain = true
+	}
+
+	// Wait for serving threads to be ready to exit.  Only then can we be sure no
+	// new conns will be created.
+	s.mu.Unlock()
+	s.serveWG.Wait()
+	s.mu.Lock()
+
+	for len(s.conns) != 0 {
+		s.cv.Wait()
+	}
+	s.conns = nil
+	if s.events != nil {
+		s.events.Finish()
+		s.events = nil
+	}
+	s.mu.Unlock()
+}
+
+// contentSubtype must be lowercase
+// cannot return nil
+func (s *Server) getCodec(contentSubtype string) baseCodec {
+	if s.opts.codec != nil {
+		return s.opts.codec
+	}
+	if contentSubtype == "" {
+		return encoding.GetCodec(proto.Name)
+	}
+	codec := encoding.GetCodec(contentSubtype)
+	if codec == nil {
+		return encoding.GetCodec(proto.Name)
+	}
+	return codec
+}
+
+// SetHeader sets the header metadata.
+// When called multiple times, all the provided metadata will be merged.
+// All the metadata will be sent out when one of the following happens:
+//  - grpc.SendHeader() is called;
+//  - The first response is sent out;
+//  - An RPC status is sent out (error or success).
+func SetHeader(ctx context.Context, md metadata.MD) error {
+	if md.Len() == 0 {
+		return nil
+	}
+	stream := ServerTransportStreamFromContext(ctx)
+	if stream == nil {
+		return status.Errorf(codes.Internal, "grpc: failed to fetch the stream from the context %v", ctx)
+	}
+	return stream.SetHeader(md)
+}
+
+// SendHeader sends header metadata. It may be called at most once.
+// The provided md and headers set by SetHeader() will be sent.
+func SendHeader(ctx context.Context, md metadata.MD) error {
+	stream := ServerTransportStreamFromContext(ctx)
+	if stream == nil {
+		return status.Errorf(codes.Internal, "grpc: failed to fetch the stream from the context %v", ctx)
+	}
+	if err := stream.SendHeader(md); err != nil {
+		return toRPCErr(err)
+	}
+	return nil
+}
+
+// SetTrailer sets the trailer metadata that will be sent when an RPC returns.
+// When called more than once, all the provided metadata will be merged.
+func SetTrailer(ctx context.Context, md metadata.MD) error {
+	if md.Len() == 0 {
+		return nil
+	}
+	stream := ServerTransportStreamFromContext(ctx)
+	if stream == nil {
+		return status.Errorf(codes.Internal, "grpc: failed to fetch the stream from the context %v", ctx)
+	}
+	return stream.SetTrailer(md)
+}
+
+// Method returns the method string for the server context.  The returned
+// string is in the format of "/service/method".
+func Method(ctx context.Context) (string, bool) {
+	s := ServerTransportStreamFromContext(ctx)
+	if s == nil {
+		return "", false
+	}
+	return s.Method(), true
+}
+
+type channelzServer struct {
+	s *Server
+}
+
+func (c *channelzServer) ChannelzMetric() *channelz.ServerInternalMetric {
+	return c.s.channelzMetric()
+}
diff --git a/go/vendor/google.golang.org/grpc/service_config.go b/go/vendor/google.golang.org/grpc/service_config.go
new file mode 100644
index 0000000..a305fe0
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/service_config.go
@@ -0,0 +1,361 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/grpclog"
+)
+
+const maxInt = int(^uint(0) >> 1)
+
+// MethodConfig defines the configuration recommended by the service providers for a
+// particular method.
+//
+// Deprecated: Users should not use this struct. Service config should be received
+// through name resolver, as specified here
+// https://github.com/grpc/grpc/blob/master/doc/service_config.md
+type MethodConfig struct {
+	// WaitForReady indicates whether RPCs sent to this method should wait until
+	// the connection is ready by default (!failfast). The value specified via the
+	// gRPC client API will override the value set here.
+	WaitForReady *bool
+	// Timeout is the default timeout for RPCs sent to this method. The actual
+	// deadline used will be the minimum of the value specified here and the value
+	// set by the application via the gRPC client API.  If either one is not set,
+	// then the other will be used.  If neither is set, then the RPC has no deadline.
+	Timeout *time.Duration
+	// MaxReqSize is the maximum allowed payload size for an individual request in a
+	// stream (client->server) in bytes. The size which is measured is the serialized
+	// payload after per-message compression (but before stream compression) in bytes.
+	// The actual value used is the minimum of the value specified here and the value set
+	// by the application via the gRPC client API. If either one is not set, then the other
+	// will be used.  If neither is set, then the built-in default is used.
+	MaxReqSize *int
+	// MaxRespSize is the maximum allowed payload size for an individual response in a
+	// stream (server->client) in bytes.
+	MaxRespSize *int
+	// RetryPolicy configures retry options for the method.
+	retryPolicy *retryPolicy
+}
+
+// ServiceConfig is provided by the service provider and contains parameters for how
+// clients that connect to the service should behave.
+//
+// Deprecated: Users should not use this struct. Service config should be received
+// through name resolver, as specified here
+// https://github.com/grpc/grpc/blob/master/doc/service_config.md
+type ServiceConfig struct {
+	// LB is the load balancer the service providers recommends. The balancer specified
+	// via grpc.WithBalancer will override this.
+	LB *string
+
+	// Methods contains a map for the methods in this service.  If there is an
+	// exact match for a method (i.e. /service/method) in the map, use the
+	// corresponding MethodConfig.  If there's no exact match, look for the
+	// default config for the service (/service/) and use the corresponding
+	// MethodConfig if it exists.  Otherwise, the method has no MethodConfig to
+	// use.
+	Methods map[string]MethodConfig
+
+	// If a retryThrottlingPolicy is provided, gRPC will automatically throttle
+	// retry attempts and hedged RPCs when the client’s ratio of failures to
+	// successes exceeds a threshold.
+	//
+	// For each server name, the gRPC client will maintain a token_count which is
+	// initially set to maxTokens, and can take values between 0 and maxTokens.
+	//
+	// Every outgoing RPC (regardless of service or method invoked) will change
+	// token_count as follows:
+	//
+	//   - Every failed RPC will decrement the token_count by 1.
+	//   - Every successful RPC will increment the token_count by tokenRatio.
+	//
+	// If token_count is less than or equal to maxTokens / 2, then RPCs will not
+	// be retried and hedged RPCs will not be sent.
+	retryThrottling *retryThrottlingPolicy
+}
+
+// retryPolicy defines the go-native version of the retry policy defined by the
+// service config here:
+// https://github.com/grpc/proposal/blob/master/A6-client-retries.md#integration-with-service-config
+type retryPolicy struct {
+	// MaxAttempts is the maximum number of attempts, including the original RPC.
+	//
+	// This field is required and must be two or greater.
+	maxAttempts int
+
+	// Exponential backoff parameters. The initial retry attempt will occur at
+	// random(0, initialBackoffMS). In general, the nth attempt will occur at
+	// random(0,
+	//   min(initialBackoffMS*backoffMultiplier**(n-1), maxBackoffMS)).
+	//
+	// These fields are required and must be greater than zero.
+	initialBackoff    time.Duration
+	maxBackoff        time.Duration
+	backoffMultiplier float64
+
+	// The set of status codes which may be retried.
+	//
+	// Status codes are specified as strings, e.g., "UNAVAILABLE".
+	//
+	// This field is required and must be non-empty.
+	// Note: a set is used to store this for easy lookup.
+	retryableStatusCodes map[codes.Code]bool
+}
+
+type jsonRetryPolicy struct {
+	MaxAttempts          int
+	InitialBackoff       string
+	MaxBackoff           string
+	BackoffMultiplier    float64
+	RetryableStatusCodes []codes.Code
+}
+
+// retryThrottlingPolicy defines the go-native version of the retry throttling
+// policy defined by the service config here:
+// https://github.com/grpc/proposal/blob/master/A6-client-retries.md#integration-with-service-config
+type retryThrottlingPolicy struct {
+	// The number of tokens starts at maxTokens. The token_count will always be
+	// between 0 and maxTokens.
+	//
+	// This field is required and must be greater than zero.
+	MaxTokens float64
+	// The amount of tokens to add on each successful RPC. Typically this will
+	// be some number between 0 and 1, e.g., 0.1.
+	//
+	// This field is required and must be greater than zero. Up to 3 decimal
+	// places are supported.
+	TokenRatio float64
+}
+
+func parseDuration(s *string) (*time.Duration, error) {
+	if s == nil {
+		return nil, nil
+	}
+	if !strings.HasSuffix(*s, "s") {
+		return nil, fmt.Errorf("malformed duration %q", *s)
+	}
+	ss := strings.SplitN((*s)[:len(*s)-1], ".", 3)
+	if len(ss) > 2 {
+		return nil, fmt.Errorf("malformed duration %q", *s)
+	}
+	// hasDigits is set if either the whole or fractional part of the number is
+	// present, since both are optional but one is required.
+	hasDigits := false
+	var d time.Duration
+	if len(ss[0]) > 0 {
+		i, err := strconv.ParseInt(ss[0], 10, 32)
+		if err != nil {
+			return nil, fmt.Errorf("malformed duration %q: %v", *s, err)
+		}
+		d = time.Duration(i) * time.Second
+		hasDigits = true
+	}
+	if len(ss) == 2 && len(ss[1]) > 0 {
+		if len(ss[1]) > 9 {
+			return nil, fmt.Errorf("malformed duration %q", *s)
+		}
+		f, err := strconv.ParseInt(ss[1], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("malformed duration %q: %v", *s, err)
+		}
+		for i := 9; i > len(ss[1]); i-- {
+			f *= 10
+		}
+		d += time.Duration(f)
+		hasDigits = true
+	}
+	if !hasDigits {
+		return nil, fmt.Errorf("malformed duration %q", *s)
+	}
+
+	return &d, nil
+}
+
+type jsonName struct {
+	Service *string
+	Method  *string
+}
+
+func (j jsonName) generatePath() (string, bool) {
+	if j.Service == nil {
+		return "", false
+	}
+	res := "/" + *j.Service + "/"
+	if j.Method != nil {
+		res += *j.Method
+	}
+	return res, true
+}
+
+// TODO(lyuxuan): delete this struct after cleaning up old service config implementation.
+type jsonMC struct {
+	Name                    *[]jsonName
+	WaitForReady            *bool
+	Timeout                 *string
+	MaxRequestMessageBytes  *int64
+	MaxResponseMessageBytes *int64
+	RetryPolicy             *jsonRetryPolicy
+}
+
+// TODO(lyuxuan): delete this struct after cleaning up old service config implementation.
+type jsonSC struct {
+	LoadBalancingPolicy *string
+	MethodConfig        *[]jsonMC
+	RetryThrottling     *retryThrottlingPolicy
+}
+
+func parseServiceConfig(js string) (ServiceConfig, error) {
+	if len(js) == 0 {
+		return ServiceConfig{}, fmt.Errorf("no JSON service config provided")
+	}
+	var rsc jsonSC
+	err := json.Unmarshal([]byte(js), &rsc)
+	if err != nil {
+		grpclog.Warningf("grpc: parseServiceConfig error unmarshaling %s due to %v", js, err)
+		return ServiceConfig{}, err
+	}
+	sc := ServiceConfig{
+		LB:              rsc.LoadBalancingPolicy,
+		Methods:         make(map[string]MethodConfig),
+		retryThrottling: rsc.RetryThrottling,
+	}
+	if rsc.MethodConfig == nil {
+		return sc, nil
+	}
+
+	for _, m := range *rsc.MethodConfig {
+		if m.Name == nil {
+			continue
+		}
+		d, err := parseDuration(m.Timeout)
+		if err != nil {
+			grpclog.Warningf("grpc: parseServiceConfig error unmarshaling %s due to %v", js, err)
+			return ServiceConfig{}, err
+		}
+
+		mc := MethodConfig{
+			WaitForReady: m.WaitForReady,
+			Timeout:      d,
+		}
+		if mc.retryPolicy, err = convertRetryPolicy(m.RetryPolicy); err != nil {
+			grpclog.Warningf("grpc: parseServiceConfig error unmarshaling %s due to %v", js, err)
+			return ServiceConfig{}, err
+		}
+		if m.MaxRequestMessageBytes != nil {
+			if *m.MaxRequestMessageBytes > int64(maxInt) {
+				mc.MaxReqSize = newInt(maxInt)
+			} else {
+				mc.MaxReqSize = newInt(int(*m.MaxRequestMessageBytes))
+			}
+		}
+		if m.MaxResponseMessageBytes != nil {
+			if *m.MaxResponseMessageBytes > int64(maxInt) {
+				mc.MaxRespSize = newInt(maxInt)
+			} else {
+				mc.MaxRespSize = newInt(int(*m.MaxResponseMessageBytes))
+			}
+		}
+		for _, n := range *m.Name {
+			if path, valid := n.generatePath(); valid {
+				sc.Methods[path] = mc
+			}
+		}
+	}
+
+	if sc.retryThrottling != nil {
+		if sc.retryThrottling.MaxTokens <= 0 ||
+			sc.retryThrottling.MaxTokens >= 1000 ||
+			sc.retryThrottling.TokenRatio <= 0 {
+			// Illegal throttling config; disable throttling.
+			sc.retryThrottling = nil
+		}
+	}
+	return sc, nil
+}
+
+func convertRetryPolicy(jrp *jsonRetryPolicy) (p *retryPolicy, err error) {
+	if jrp == nil {
+		return nil, nil
+	}
+	ib, err := parseDuration(&jrp.InitialBackoff)
+	if err != nil {
+		return nil, err
+	}
+	mb, err := parseDuration(&jrp.MaxBackoff)
+	if err != nil {
+		return nil, err
+	}
+
+	if jrp.MaxAttempts <= 1 ||
+		*ib <= 0 ||
+		*mb <= 0 ||
+		jrp.BackoffMultiplier <= 0 ||
+		len(jrp.RetryableStatusCodes) == 0 {
+		grpclog.Warningf("grpc: ignoring retry policy %v due to illegal configuration", jrp)
+		return nil, nil
+	}
+
+	rp := &retryPolicy{
+		maxAttempts:          jrp.MaxAttempts,
+		initialBackoff:       *ib,
+		maxBackoff:           *mb,
+		backoffMultiplier:    jrp.BackoffMultiplier,
+		retryableStatusCodes: make(map[codes.Code]bool),
+	}
+	if rp.maxAttempts > 5 {
+		// TODO(retry): Make the max maxAttempts configurable.
+		rp.maxAttempts = 5
+	}
+	for _, code := range jrp.RetryableStatusCodes {
+		rp.retryableStatusCodes[code] = true
+	}
+	return rp, nil
+}
+
+func min(a, b *int) *int {
+	if *a < *b {
+		return a
+	}
+	return b
+}
+
+func getMaxSize(mcMax, doptMax *int, defaultVal int) *int {
+	if mcMax == nil && doptMax == nil {
+		return &defaultVal
+	}
+	if mcMax != nil && doptMax != nil {
+		return min(mcMax, doptMax)
+	}
+	if mcMax != nil {
+		return mcMax
+	}
+	return doptMax
+}
+
+func newInt(b int) *int {
+	return &b
+}
diff --git a/go/vendor/google.golang.org/grpc/stats/handlers.go b/go/vendor/google.golang.org/grpc/stats/handlers.go
new file mode 100644
index 0000000..05b384c
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/stats/handlers.go
@@ -0,0 +1,64 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package stats
+
+import (
+	"net"
+
+	"golang.org/x/net/context"
+)
+
+// ConnTagInfo defines the relevant information needed by connection context tagger.
+type ConnTagInfo struct {
+	// RemoteAddr is the remote address of the corresponding connection.
+	RemoteAddr net.Addr
+	// LocalAddr is the local address of the corresponding connection.
+	LocalAddr net.Addr
+}
+
+// RPCTagInfo defines the relevant information needed by RPC context tagger.
+type RPCTagInfo struct {
+	// FullMethodName is the RPC method in the format of /package.service/method.
+	FullMethodName string
+	// FailFast indicates if this RPC is failfast.
+	// This field is only valid on client side, it's always false on server side.
+	FailFast bool
+}
+
+// Handler defines the interface for the related stats handling (e.g., RPCs, connections).
+type Handler interface {
+	// TagRPC can attach some information to the given context.
+	// The context used for the rest lifetime of the RPC will be derived from
+	// the returned context.
+	TagRPC(context.Context, *RPCTagInfo) context.Context
+	// HandleRPC processes the RPC stats.
+	HandleRPC(context.Context, RPCStats)
+
+	// TagConn can attach some information to the given context.
+	// The returned context will be used for stats handling.
+	// For conn stats handling, the context used in HandleConn for this
+	// connection will be derived from the context returned.
+	// For RPC stats handling,
+	//  - On server side, the context used in HandleRPC for all RPCs on this
+	// connection will be derived from the context returned.
+	//  - On client side, the context is not derived from the context returned.
+	TagConn(context.Context, *ConnTagInfo) context.Context
+	// HandleConn processes the Conn stats.
+	HandleConn(context.Context, ConnStats)
+}
diff --git a/go/vendor/google.golang.org/grpc/stats/stats.go b/go/vendor/google.golang.org/grpc/stats/stats.go
new file mode 100644
index 0000000..3f13190
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/stats/stats.go
@@ -0,0 +1,296 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+//go:generate protoc --go_out=plugins=grpc:. grpc_testing/test.proto
+
+// Package stats is for collecting and reporting various network and RPC stats.
+// This package is for monitoring purpose only. All fields are read-only.
+// All APIs are experimental.
+package stats // import "google.golang.org/grpc/stats"
+
+import (
+	"net"
+	"time"
+
+	"golang.org/x/net/context"
+)
+
+// RPCStats contains stats information about RPCs.
+type RPCStats interface {
+	isRPCStats()
+	// IsClient returns true if this RPCStats is from client side.
+	IsClient() bool
+}
+
+// Begin contains stats when an RPC begins.
+// FailFast is only valid if this Begin is from client side.
+type Begin struct {
+	// Client is true if this Begin is from client side.
+	Client bool
+	// BeginTime is the time when the RPC begins.
+	BeginTime time.Time
+	// FailFast indicates if this RPC is failfast.
+	FailFast bool
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *Begin) IsClient() bool { return s.Client }
+
+func (s *Begin) isRPCStats() {}
+
+// InPayload contains the information for an incoming payload.
+type InPayload struct {
+	// Client is true if this InPayload is from client side.
+	Client bool
+	// Payload is the payload with original type.
+	Payload interface{}
+	// Data is the serialized message payload.
+	Data []byte
+	// Length is the length of uncompressed data.
+	Length int
+	// WireLength is the length of data on wire (compressed, signed, encrypted).
+	WireLength int
+	// RecvTime is the time when the payload is received.
+	RecvTime time.Time
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *InPayload) IsClient() bool { return s.Client }
+
+func (s *InPayload) isRPCStats() {}
+
+// InHeader contains stats when a header is received.
+type InHeader struct {
+	// Client is true if this InHeader is from client side.
+	Client bool
+	// WireLength is the wire length of header.
+	WireLength int
+
+	// The following fields are valid only if Client is false.
+	// FullMethod is the full RPC method string, i.e., /package.service/method.
+	FullMethod string
+	// RemoteAddr is the remote address of the corresponding connection.
+	RemoteAddr net.Addr
+	// LocalAddr is the local address of the corresponding connection.
+	LocalAddr net.Addr
+	// Compression is the compression algorithm used for the RPC.
+	Compression string
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *InHeader) IsClient() bool { return s.Client }
+
+func (s *InHeader) isRPCStats() {}
+
+// InTrailer contains stats when a trailer is received.
+type InTrailer struct {
+	// Client is true if this InTrailer is from client side.
+	Client bool
+	// WireLength is the wire length of trailer.
+	WireLength int
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *InTrailer) IsClient() bool { return s.Client }
+
+func (s *InTrailer) isRPCStats() {}
+
+// OutPayload contains the information for an outgoing payload.
+type OutPayload struct {
+	// Client is true if this OutPayload is from client side.
+	Client bool
+	// Payload is the payload with original type.
+	Payload interface{}
+	// Data is the serialized message payload.
+	Data []byte
+	// Length is the length of uncompressed data.
+	Length int
+	// WireLength is the length of data on wire (compressed, signed, encrypted).
+	WireLength int
+	// SentTime is the time when the payload is sent.
+	SentTime time.Time
+}
+
+// IsClient indicates if this stats information is from client side.
+func (s *OutPayload) IsClient() bool { return s.Client }
+
+func (s *OutPayload) isRPCStats() {}
+
+// OutHeader contains stats when a header is sent.
+type OutHeader struct {
+	// Client is true if this OutHeader is from client side.
+	Client bool
+
+	// The following fields are valid only if Client is true.
+	// FullMethod is the full RPC method string, i.e., /package.service/method.
+	FullMethod string
+	// RemoteAddr is the remote address of the corresponding connection.
+	RemoteAddr net.Addr
+	// LocalAddr is the local address of the corresponding connection.
+	LocalAddr net.Addr
+	// Compression is the compression algorithm used for the RPC.
+	Compression string
+}
+
+// IsClient indicates if this stats information is from client side.
+func (s *OutHeader) IsClient() bool { return s.Client }
+
+func (s *OutHeader) isRPCStats() {}
+
+// OutTrailer contains stats when a trailer is sent.
+type OutTrailer struct {
+	// Client is true if this OutTrailer is from client side.
+	Client bool
+	// WireLength is the wire length of trailer.
+	WireLength int
+}
+
+// IsClient indicates if this stats information is from client side.
+func (s *OutTrailer) IsClient() bool { return s.Client }
+
+func (s *OutTrailer) isRPCStats() {}
+
+// End contains stats when an RPC ends.
+type End struct {
+	// Client is true if this End is from client side.
+	Client bool
+	// BeginTime is the time when the RPC began.
+	BeginTime time.Time
+	// EndTime is the time when the RPC ends.
+	EndTime time.Time
+	// Error is the error the RPC ended with. It is an error generated from
+	// status.Status and can be converted back to status.Status using
+	// status.FromError if non-nil.
+	Error error
+}
+
+// IsClient indicates if this is from client side.
+func (s *End) IsClient() bool { return s.Client }
+
+func (s *End) isRPCStats() {}
+
+// ConnStats contains stats information about connections.
+type ConnStats interface {
+	isConnStats()
+	// IsClient returns true if this ConnStats is from client side.
+	IsClient() bool
+}
+
+// ConnBegin contains the stats of a connection when it is established.
+type ConnBegin struct {
+	// Client is true if this ConnBegin is from client side.
+	Client bool
+}
+
+// IsClient indicates if this is from client side.
+func (s *ConnBegin) IsClient() bool { return s.Client }
+
+func (s *ConnBegin) isConnStats() {}
+
+// ConnEnd contains the stats of a connection when it ends.
+type ConnEnd struct {
+	// Client is true if this ConnEnd is from client side.
+	Client bool
+}
+
+// IsClient indicates if this is from client side.
+func (s *ConnEnd) IsClient() bool { return s.Client }
+
+func (s *ConnEnd) isConnStats() {}
+
+type incomingTagsKey struct{}
+type outgoingTagsKey struct{}
+
+// SetTags attaches stats tagging data to the context, which will be sent in
+// the outgoing RPC with the header grpc-tags-bin.  Subsequent calls to
+// SetTags will overwrite the values from earlier calls.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func SetTags(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, outgoingTagsKey{}, b)
+}
+
+// Tags returns the tags from the context for the inbound RPC.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func Tags(ctx context.Context) []byte {
+	b, _ := ctx.Value(incomingTagsKey{}).([]byte)
+	return b
+}
+
+// SetIncomingTags attaches stats tagging data to the context, to be read by
+// the application (not sent in outgoing RPCs).
+//
+// This is intended for gRPC-internal use ONLY.
+func SetIncomingTags(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, incomingTagsKey{}, b)
+}
+
+// OutgoingTags returns the tags from the context for the outbound RPC.
+//
+// This is intended for gRPC-internal use ONLY.
+func OutgoingTags(ctx context.Context) []byte {
+	b, _ := ctx.Value(outgoingTagsKey{}).([]byte)
+	return b
+}
+
+type incomingTraceKey struct{}
+type outgoingTraceKey struct{}
+
+// SetTrace attaches stats tagging data to the context, which will be sent in
+// the outgoing RPC with the header grpc-trace-bin.  Subsequent calls to
+// SetTrace will overwrite the values from earlier calls.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func SetTrace(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, outgoingTraceKey{}, b)
+}
+
+// Trace returns the trace from the context for the inbound RPC.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func Trace(ctx context.Context) []byte {
+	b, _ := ctx.Value(incomingTraceKey{}).([]byte)
+	return b
+}
+
+// SetIncomingTrace attaches stats tagging data to the context, to be read by
+// the application (not sent in outgoing RPCs).  It is intended for
+// gRPC-internal use.
+func SetIncomingTrace(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, incomingTraceKey{}, b)
+}
+
+// OutgoingTrace returns the trace from the context for the outbound RPC.  It is
+// intended for gRPC-internal use.
+func OutgoingTrace(ctx context.Context) []byte {
+	b, _ := ctx.Value(outgoingTraceKey{}).([]byte)
+	return b
+}
diff --git a/go/vendor/google.golang.org/grpc/status/go16.go b/go/vendor/google.golang.org/grpc/status/go16.go
new file mode 100644
index 0000000..e59b53e
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/status/go16.go
@@ -0,0 +1,42 @@
+// +build go1.6,!go1.7
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package status
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+)
+
+// FromContextError converts a context error into a Status.  It returns a
+// Status with codes.OK if err is nil, or a Status with codes.Unknown if err is
+// non-nil and not a context error.
+func FromContextError(err error) *Status {
+	switch err {
+	case nil:
+		return New(codes.OK, "")
+	case context.DeadlineExceeded:
+		return New(codes.DeadlineExceeded, err.Error())
+	case context.Canceled:
+		return New(codes.Canceled, err.Error())
+	default:
+		return New(codes.Unknown, err.Error())
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/status/go17.go b/go/vendor/google.golang.org/grpc/status/go17.go
new file mode 100644
index 0000000..0902151
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/status/go17.go
@@ -0,0 +1,44 @@
+// +build go1.7
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package status
+
+import (
+	"context"
+
+	netctx "golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+)
+
+// FromContextError converts a context error into a Status.  It returns a
+// Status with codes.OK if err is nil, or a Status with codes.Unknown if err is
+// non-nil and not a context error.
+func FromContextError(err error) *Status {
+	switch err {
+	case nil:
+		return New(codes.OK, "")
+	case context.DeadlineExceeded, netctx.DeadlineExceeded:
+		return New(codes.DeadlineExceeded, err.Error())
+	case context.Canceled, netctx.Canceled:
+		return New(codes.Canceled, err.Error())
+	default:
+		return New(codes.Unknown, err.Error())
+	}
+}
diff --git a/go/vendor/google.golang.org/grpc/status/status.go b/go/vendor/google.golang.org/grpc/status/status.go
new file mode 100644
index 0000000..897321b
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/status/status.go
@@ -0,0 +1,193 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package status implements errors returned by gRPC.  These errors are
+// serialized and transmitted on the wire between server and client, and allow
+// for additional data to be transmitted via the Details field in the status
+// proto.  gRPC service handlers should return an error created by this
+// package, and gRPC clients should expect a corresponding error to be
+// returned from the RPC call.
+//
+// This package upholds the invariants that a non-nil error may not
+// contain an OK code, and an OK code must result in a nil error.
+package status
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/golang/protobuf/proto"
+	"github.com/golang/protobuf/ptypes"
+	spb "google.golang.org/genproto/googleapis/rpc/status"
+	"google.golang.org/grpc/codes"
+)
+
+// statusError is an alias of a status proto.  It implements error and Status,
+// and a nil statusError should never be returned by this package.
+type statusError spb.Status
+
+func (se *statusError) Error() string {
+	p := (*spb.Status)(se)
+	return fmt.Sprintf("rpc error: code = %s desc = %s", codes.Code(p.GetCode()), p.GetMessage())
+}
+
+func (se *statusError) GRPCStatus() *Status {
+	return &Status{s: (*spb.Status)(se)}
+}
+
+// Status represents an RPC status code, message, and details.  It is immutable
+// and should be created with New, Newf, or FromProto.
+type Status struct {
+	s *spb.Status
+}
+
+// Code returns the status code contained in s.
+func (s *Status) Code() codes.Code {
+	if s == nil || s.s == nil {
+		return codes.OK
+	}
+	return codes.Code(s.s.Code)
+}
+
+// Message returns the message contained in s.
+func (s *Status) Message() string {
+	if s == nil || s.s == nil {
+		return ""
+	}
+	return s.s.Message
+}
+
+// Proto returns s's status as an spb.Status proto message.
+func (s *Status) Proto() *spb.Status {
+	if s == nil {
+		return nil
+	}
+	return proto.Clone(s.s).(*spb.Status)
+}
+
+// Err returns an immutable error representing s; returns nil if s.Code() is
+// OK.
+func (s *Status) Err() error {
+	if s.Code() == codes.OK {
+		return nil
+	}
+	return (*statusError)(s.s)
+}
+
+// New returns a Status representing c and msg.
+func New(c codes.Code, msg string) *Status {
+	return &Status{s: &spb.Status{Code: int32(c), Message: msg}}
+}
+
+// Newf returns New(c, fmt.Sprintf(format, a...)).
+func Newf(c codes.Code, format string, a ...interface{}) *Status {
+	return New(c, fmt.Sprintf(format, a...))
+}
+
+// Error returns an error representing c and msg.  If c is OK, returns nil.
+func Error(c codes.Code, msg string) error {
+	return New(c, msg).Err()
+}
+
+// Errorf returns Error(c, fmt.Sprintf(format, a...)).
+func Errorf(c codes.Code, format string, a ...interface{}) error {
+	return Error(c, fmt.Sprintf(format, a...))
+}
+
+// ErrorProto returns an error representing s.  If s.Code is OK, returns nil.
+func ErrorProto(s *spb.Status) error {
+	return FromProto(s).Err()
+}
+
+// FromProto returns a Status representing s.
+func FromProto(s *spb.Status) *Status {
+	return &Status{s: proto.Clone(s).(*spb.Status)}
+}
+
+// FromError returns a Status representing err if it was produced from this
+// package or has a method `GRPCStatus() *Status`. Otherwise, ok is false and a
+// Status is returned with codes.Unknown and the original error message.
+func FromError(err error) (s *Status, ok bool) {
+	if err == nil {
+		return &Status{s: &spb.Status{Code: int32(codes.OK)}}, true
+	}
+	if se, ok := err.(interface {
+		GRPCStatus() *Status
+	}); ok {
+		return se.GRPCStatus(), true
+	}
+	return New(codes.Unknown, err.Error()), false
+}
+
+// Convert is a convenience function which removes the need to handle the
+// boolean return value from FromError.
+func Convert(err error) *Status {
+	s, _ := FromError(err)
+	return s
+}
+
+// WithDetails returns a new status with the provided details messages appended to the status.
+// If any errors are encountered, it returns nil and the first error encountered.
+func (s *Status) WithDetails(details ...proto.Message) (*Status, error) {
+	if s.Code() == codes.OK {
+		return nil, errors.New("no error details for status with code OK")
+	}
+	// s.Code() != OK implies that s.Proto() != nil.
+	p := s.Proto()
+	for _, detail := range details {
+		any, err := ptypes.MarshalAny(detail)
+		if err != nil {
+			return nil, err
+		}
+		p.Details = append(p.Details, any)
+	}
+	return &Status{s: p}, nil
+}
+
+// Details returns a slice of details messages attached to the status.
+// If a detail cannot be decoded, the error is returned in place of the detail.
+func (s *Status) Details() []interface{} {
+	if s == nil || s.s == nil {
+		return nil
+	}
+	details := make([]interface{}, 0, len(s.s.Details))
+	for _, any := range s.s.Details {
+		detail := &ptypes.DynamicAny{}
+		if err := ptypes.UnmarshalAny(any, detail); err != nil {
+			details = append(details, err)
+			continue
+		}
+		details = append(details, detail.Message)
+	}
+	return details
+}
+
+// Code returns the Code of the error if it is a Status error, codes.OK if err
+// is nil, or codes.Unknown otherwise.
+func Code(err error) codes.Code {
+	// Don't use FromError to avoid allocation of OK status.
+	if err == nil {
+		return codes.OK
+	}
+	if se, ok := err.(interface {
+		GRPCStatus() *Status
+	}); ok {
+		return se.GRPCStatus().Code()
+	}
+	return codes.Unknown
+}
diff --git a/go/vendor/google.golang.org/grpc/stream.go b/go/vendor/google.golang.org/grpc/stream.go
new file mode 100644
index 0000000..b71eb31
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/stream.go
@@ -0,0 +1,1033 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"errors"
+	"io"
+	"math"
+	"strconv"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/trace"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/encoding"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/internal/grpcrand"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+)
+
+// StreamHandler defines the handler called by gRPC server to complete the
+// execution of a streaming RPC. If a StreamHandler returns an error, it
+// should be produced by the status package, or else gRPC will use
+// codes.Unknown as the status code and err.Error() as the status message
+// of the RPC.
+type StreamHandler func(srv interface{}, stream ServerStream) error
+
+// StreamDesc represents a streaming RPC service's method specification.
+type StreamDesc struct {
+	StreamName string
+	Handler    StreamHandler
+
+	// At least one of these is true.
+	ServerStreams bool
+	ClientStreams bool
+}
+
+// Stream defines the common interface a client or server stream has to satisfy.
+//
+// Deprecated: See ClientStream and ServerStream documentation instead.
+type Stream interface {
+	// Deprecated: See ClientStream and ServerStream documentation instead.
+	Context() context.Context
+	// Deprecated: See ClientStream and ServerStream documentation instead.
+	SendMsg(m interface{}) error
+	// Deprecated: See ClientStream and ServerStream documentation instead.
+	RecvMsg(m interface{}) error
+}
+
+// ClientStream defines the client-side behavior of a streaming RPC.
+//
+// All errors returned from ClientStream methods are compatible with the
+// status package.
+type ClientStream interface {
+	// Header returns the header metadata received from the server if there
+	// is any. It blocks if the metadata is not ready to read.
+	Header() (metadata.MD, error)
+	// Trailer returns the trailer metadata from the server, if there is any.
+	// It must only be called after stream.CloseAndRecv has returned, or
+	// stream.Recv has returned a non-nil error (including io.EOF).
+	Trailer() metadata.MD
+	// CloseSend closes the send direction of the stream. It closes the stream
+	// when non-nil error is met.
+	CloseSend() error
+	// Context returns the context for this stream.
+	//
+	// It should not be called until after Header or RecvMsg has returned. Once
+	// called, subsequent client-side retries are disabled.
+	Context() context.Context
+	// SendMsg is generally called by generated code. On error, SendMsg aborts
+	// the stream. If the error was generated by the client, the status is
+	// returned directly; otherwise, io.EOF is returned and the status of
+	// the stream may be discovered using RecvMsg.
+	//
+	// SendMsg blocks until:
+	//   - There is sufficient flow control to schedule m with the transport, or
+	//   - The stream is done, or
+	//   - The stream breaks.
+	//
+	// SendMsg does not wait until the message is received by the server. An
+	// untimely stream closure may result in lost messages. To ensure delivery,
+	// users should ensure the RPC completed successfully using RecvMsg.
+	//
+	// It is safe to have a goroutine calling SendMsg and another goroutine
+	// calling RecvMsg on the same stream at the same time, but it is not safe
+	// to call SendMsg on the same stream in different goroutines.
+	SendMsg(m interface{}) error
+	// RecvMsg blocks until it receives a message into m or the stream is
+	// done. It returns io.EOF when the stream completes successfully. On
+	// any other error, the stream is aborted and the error contains the RPC
+	// status.
+	//
+	// It is safe to have a goroutine calling SendMsg and another goroutine
+	// calling RecvMsg on the same stream at the same time, but it is not
+	// safe to call RecvMsg on the same stream in different goroutines.
+	RecvMsg(m interface{}) error
+}
+
+// NewStream creates a new Stream for the client side. This is typically
+// called by generated code. ctx is used for the lifetime of the stream.
+//
+// To ensure resources are not leaked due to the stream returned, one of the following
+// actions must be performed:
+//
+//      1. Call Close on the ClientConn.
+//      2. Cancel the context provided.
+//      3. Call RecvMsg until a non-nil error is returned. A protobuf-generated
+//         client-streaming RPC, for instance, might use the helper function
+//         CloseAndRecv (note that CloseSend does not Recv, therefore is not
+//         guaranteed to release all resources).
+//      4. Receive a non-nil, non-io.EOF error from Header or SendMsg.
+//
+// If none of the above happen, a goroutine and a context will be leaked, and grpc
+// will not call the optionally-configured stats handler with a stats.End message.
+func (cc *ClientConn) NewStream(ctx context.Context, desc *StreamDesc, method string, opts ...CallOption) (ClientStream, error) {
+	// allow interceptor to see all applicable call options, which means those
+	// configured as defaults from dial option as well as per-call options
+	opts = combine(cc.dopts.callOptions, opts)
+
+	if cc.dopts.streamInt != nil {
+		return cc.dopts.streamInt(ctx, desc, cc, method, newClientStream, opts...)
+	}
+	return newClientStream(ctx, desc, cc, method, opts...)
+}
+
+// NewClientStream is a wrapper for ClientConn.NewStream.
+func NewClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, opts ...CallOption) (ClientStream, error) {
+	return cc.NewStream(ctx, desc, method, opts...)
+}
+
+func newClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, opts ...CallOption) (_ ClientStream, err error) {
+	if channelz.IsOn() {
+		cc.incrCallsStarted()
+		defer func() {
+			if err != nil {
+				cc.incrCallsFailed()
+			}
+		}()
+	}
+	c := defaultCallInfo()
+	mc := cc.GetMethodConfig(method)
+	if mc.WaitForReady != nil {
+		c.failFast = !*mc.WaitForReady
+	}
+
+	// Possible context leak:
+	// The cancel function for the child context we create will only be called
+	// when RecvMsg returns a non-nil error, if the ClientConn is closed, or if
+	// an error is generated by SendMsg.
+	// https://github.com/grpc/grpc-go/issues/1818.
+	var cancel context.CancelFunc
+	if mc.Timeout != nil && *mc.Timeout >= 0 {
+		ctx, cancel = context.WithTimeout(ctx, *mc.Timeout)
+	} else {
+		ctx, cancel = context.WithCancel(ctx)
+	}
+	defer func() {
+		if err != nil {
+			cancel()
+		}
+	}()
+
+	for _, o := range opts {
+		if err := o.before(c); err != nil {
+			return nil, toRPCErr(err)
+		}
+	}
+	c.maxSendMessageSize = getMaxSize(mc.MaxReqSize, c.maxSendMessageSize, defaultClientMaxSendMessageSize)
+	c.maxReceiveMessageSize = getMaxSize(mc.MaxRespSize, c.maxReceiveMessageSize, defaultClientMaxReceiveMessageSize)
+	if err := setCallInfoCodec(c); err != nil {
+		return nil, err
+	}
+
+	callHdr := &transport.CallHdr{
+		Host:           cc.authority,
+		Method:         method,
+		ContentSubtype: c.contentSubtype,
+	}
+
+	// Set our outgoing compression according to the UseCompressor CallOption, if
+	// set.  In that case, also find the compressor from the encoding package.
+	// Otherwise, use the compressor configured by the WithCompressor DialOption,
+	// if set.
+	var cp Compressor
+	var comp encoding.Compressor
+	if ct := c.compressorType; ct != "" {
+		callHdr.SendCompress = ct
+		if ct != encoding.Identity {
+			comp = encoding.GetCompressor(ct)
+			if comp == nil {
+				return nil, status.Errorf(codes.Internal, "grpc: Compressor is not installed for requested grpc-encoding %q", ct)
+			}
+		}
+	} else if cc.dopts.cp != nil {
+		callHdr.SendCompress = cc.dopts.cp.Type()
+		cp = cc.dopts.cp
+	}
+	if c.creds != nil {
+		callHdr.Creds = c.creds
+	}
+	var trInfo traceInfo
+	if EnableTracing {
+		trInfo.tr = trace.New("grpc.Sent."+methodFamily(method), method)
+		trInfo.firstLine.client = true
+		if deadline, ok := ctx.Deadline(); ok {
+			trInfo.firstLine.deadline = deadline.Sub(time.Now())
+		}
+		trInfo.tr.LazyLog(&trInfo.firstLine, false)
+		ctx = trace.NewContext(ctx, trInfo.tr)
+	}
+	ctx = newContextWithRPCInfo(ctx, c.failFast)
+	sh := cc.dopts.copts.StatsHandler
+	var beginTime time.Time
+	if sh != nil {
+		ctx = sh.TagRPC(ctx, &stats.RPCTagInfo{FullMethodName: method, FailFast: c.failFast})
+		beginTime = time.Now()
+		begin := &stats.Begin{
+			Client:    true,
+			BeginTime: beginTime,
+			FailFast:  c.failFast,
+		}
+		sh.HandleRPC(ctx, begin)
+	}
+
+	cs := &clientStream{
+		callHdr:      callHdr,
+		ctx:          ctx,
+		methodConfig: &mc,
+		opts:         opts,
+		callInfo:     c,
+		cc:           cc,
+		desc:         desc,
+		codec:        c.codec,
+		cp:           cp,
+		comp:         comp,
+		cancel:       cancel,
+		beginTime:    beginTime,
+		firstAttempt: true,
+	}
+	if !cc.dopts.disableRetry {
+		cs.retryThrottler = cc.retryThrottler.Load().(*retryThrottler)
+	}
+
+	cs.callInfo.stream = cs
+	// Only this initial attempt has stats/tracing.
+	// TODO(dfawley): move to newAttempt when per-attempt stats are implemented.
+	if err := cs.newAttemptLocked(sh, trInfo); err != nil {
+		cs.finish(err)
+		return nil, err
+	}
+
+	op := func(a *csAttempt) error { return a.newStream() }
+	if err := cs.withRetry(op, func() { cs.bufferForRetryLocked(0, op) }); err != nil {
+		cs.finish(err)
+		return nil, err
+	}
+
+	if desc != unaryStreamDesc {
+		// Listen on cc and stream contexts to cleanup when the user closes the
+		// ClientConn or cancels the stream context.  In all other cases, an error
+		// should already be injected into the recv buffer by the transport, which
+		// the client will eventually receive, and then we will cancel the stream's
+		// context in clientStream.finish.
+		go func() {
+			select {
+			case <-cc.ctx.Done():
+				cs.finish(ErrClientConnClosing)
+			case <-ctx.Done():
+				cs.finish(toRPCErr(ctx.Err()))
+			}
+		}()
+	}
+	return cs, nil
+}
+
+func (cs *clientStream) newAttemptLocked(sh stats.Handler, trInfo traceInfo) error {
+	cs.attempt = &csAttempt{
+		cs:           cs,
+		dc:           cs.cc.dopts.dc,
+		statsHandler: sh,
+		trInfo:       trInfo,
+	}
+
+	if err := cs.ctx.Err(); err != nil {
+		return toRPCErr(err)
+	}
+	t, done, err := cs.cc.getTransport(cs.ctx, cs.callInfo.failFast, cs.callHdr.Method)
+	if err != nil {
+		return err
+	}
+	cs.attempt.t = t
+	cs.attempt.done = done
+	return nil
+}
+
+func (a *csAttempt) newStream() error {
+	cs := a.cs
+	cs.callHdr.PreviousAttempts = cs.numRetries
+	s, err := a.t.NewStream(cs.ctx, cs.callHdr)
+	if err != nil {
+		return toRPCErr(err)
+	}
+	cs.attempt.s = s
+	cs.attempt.p = &parser{r: s}
+	return nil
+}
+
+// clientStream implements a client side Stream.
+type clientStream struct {
+	callHdr  *transport.CallHdr
+	opts     []CallOption
+	callInfo *callInfo
+	cc       *ClientConn
+	desc     *StreamDesc
+
+	codec baseCodec
+	cp    Compressor
+	comp  encoding.Compressor
+
+	cancel context.CancelFunc // cancels all attempts
+
+	sentLast  bool // sent an end stream
+	beginTime time.Time
+
+	methodConfig *MethodConfig
+
+	ctx context.Context // the application's context, wrapped by stats/tracing
+
+	retryThrottler *retryThrottler // The throttler active when the RPC began.
+
+	mu                      sync.Mutex
+	firstAttempt            bool       // if true, transparent retry is valid
+	numRetries              int        // exclusive of transparent retry attempt(s)
+	numRetriesSincePushback int        // retries since pushback; to reset backoff
+	finished                bool       // TODO: replace with atomic cmpxchg or sync.Once?
+	attempt                 *csAttempt // the active client stream attempt
+	// TODO(hedging): hedging will have multiple attempts simultaneously.
+	committed  bool                       // active attempt committed for retry?
+	buffer     []func(a *csAttempt) error // operations to replay on retry
+	bufferSize int                        // current size of buffer
+}
+
+// csAttempt implements a single transport stream attempt within a
+// clientStream.
+type csAttempt struct {
+	cs   *clientStream
+	t    transport.ClientTransport
+	s    *transport.Stream
+	p    *parser
+	done func(balancer.DoneInfo)
+
+	finished  bool
+	dc        Decompressor
+	decomp    encoding.Compressor
+	decompSet bool
+
+	mu sync.Mutex // guards trInfo.tr
+	// trInfo.tr is set when created (if EnableTracing is true),
+	// and cleared when the finish method is called.
+	trInfo traceInfo
+
+	statsHandler stats.Handler
+}
+
+func (cs *clientStream) commitAttemptLocked() {
+	cs.committed = true
+	cs.buffer = nil
+}
+
+func (cs *clientStream) commitAttempt() {
+	cs.mu.Lock()
+	cs.commitAttemptLocked()
+	cs.mu.Unlock()
+}
+
+// shouldRetry returns nil if the RPC should be retried; otherwise it returns
+// the error that should be returned by the operation.
+func (cs *clientStream) shouldRetry(err error) error {
+	if cs.attempt.s == nil && !cs.callInfo.failFast {
+		// In the event of any error from NewStream (attempt.s == nil), we
+		// never attempted to write anything to the wire, so we can retry
+		// indefinitely for non-fail-fast RPCs.
+		return nil
+	}
+	if cs.finished || cs.committed {
+		// RPC is finished or committed; cannot retry.
+		return err
+	}
+	// Wait for the trailers.
+	if cs.attempt.s != nil {
+		<-cs.attempt.s.Done()
+	}
+	if cs.firstAttempt && !cs.callInfo.failFast && (cs.attempt.s == nil || cs.attempt.s.Unprocessed()) {
+		// First attempt, wait-for-ready, stream unprocessed: transparently retry.
+		cs.firstAttempt = false
+		return nil
+	}
+	cs.firstAttempt = false
+	if cs.cc.dopts.disableRetry {
+		return err
+	}
+
+	pushback := 0
+	hasPushback := false
+	if cs.attempt.s != nil {
+		if to, toErr := cs.attempt.s.TrailersOnly(); toErr != nil {
+			// Context error; stop now.
+			return toErr
+		} else if !to {
+			return err
+		}
+
+		// TODO(retry): Move down if the spec changes to not check server pushback
+		// before considering this a failure for throttling.
+		sps := cs.attempt.s.Trailer()["grpc-retry-pushback-ms"]
+		if len(sps) == 1 {
+			var e error
+			if pushback, e = strconv.Atoi(sps[0]); e != nil || pushback < 0 {
+				grpclog.Infof("Server retry pushback specified to abort (%q).", sps[0])
+				cs.retryThrottler.throttle() // This counts as a failure for throttling.
+				return err
+			}
+			hasPushback = true
+		} else if len(sps) > 1 {
+			grpclog.Warningf("Server retry pushback specified multiple values (%q); not retrying.", sps)
+			cs.retryThrottler.throttle() // This counts as a failure for throttling.
+			return err
+		}
+	}
+
+	var code codes.Code
+	if cs.attempt.s != nil {
+		code = cs.attempt.s.Status().Code()
+	} else {
+		code = status.Convert(err).Code()
+	}
+
+	rp := cs.methodConfig.retryPolicy
+	if rp == nil || !rp.retryableStatusCodes[code] {
+		return err
+	}
+
+	// Note: the ordering here is important; we count this as a failure
+	// only if the code matched a retryable code.
+	if cs.retryThrottler.throttle() {
+		return err
+	}
+	if cs.numRetries+1 >= rp.maxAttempts {
+		return err
+	}
+
+	var dur time.Duration
+	if hasPushback {
+		dur = time.Millisecond * time.Duration(pushback)
+		cs.numRetriesSincePushback = 0
+	} else {
+		fact := math.Pow(rp.backoffMultiplier, float64(cs.numRetriesSincePushback))
+		cur := float64(rp.initialBackoff) * fact
+		if max := float64(rp.maxBackoff); cur > max {
+			cur = max
+		}
+		dur = time.Duration(grpcrand.Int63n(int64(cur)))
+		cs.numRetriesSincePushback++
+	}
+
+	// TODO(dfawley): we could eagerly fail here if dur puts us past the
+	// deadline, but unsure if it is worth doing.
+	t := time.NewTimer(dur)
+	select {
+	case <-t.C:
+		cs.numRetries++
+		return nil
+	case <-cs.ctx.Done():
+		t.Stop()
+		return status.FromContextError(cs.ctx.Err()).Err()
+	}
+}
+
+// Returns nil if a retry was performed and succeeded; error otherwise.
+func (cs *clientStream) retryLocked(lastErr error) error {
+	for {
+		cs.attempt.finish(lastErr)
+		if err := cs.shouldRetry(lastErr); err != nil {
+			cs.commitAttemptLocked()
+			return err
+		}
+		if err := cs.newAttemptLocked(nil, traceInfo{}); err != nil {
+			return err
+		}
+		if lastErr = cs.replayBufferLocked(); lastErr == nil {
+			return nil
+		}
+	}
+}
+
+func (cs *clientStream) Context() context.Context {
+	cs.commitAttempt()
+	// No need to lock before using attempt, since we know it is committed and
+	// cannot change.
+	return cs.attempt.s.Context()
+}
+
+func (cs *clientStream) withRetry(op func(a *csAttempt) error, onSuccess func()) error {
+	cs.mu.Lock()
+	for {
+		if cs.committed {
+			cs.mu.Unlock()
+			return op(cs.attempt)
+		}
+		a := cs.attempt
+		cs.mu.Unlock()
+		err := op(a)
+		cs.mu.Lock()
+		if a != cs.attempt {
+			// We started another attempt already.
+			continue
+		}
+		if err == io.EOF {
+			<-a.s.Done()
+		}
+		if err == nil || (err == io.EOF && a.s.Status().Code() == codes.OK) {
+			onSuccess()
+			cs.mu.Unlock()
+			return err
+		}
+		if err := cs.retryLocked(err); err != nil {
+			cs.mu.Unlock()
+			return err
+		}
+	}
+}
+
+func (cs *clientStream) Header() (metadata.MD, error) {
+	var m metadata.MD
+	err := cs.withRetry(func(a *csAttempt) error {
+		var err error
+		m, err = a.s.Header()
+		return toRPCErr(err)
+	}, cs.commitAttemptLocked)
+	if err != nil {
+		cs.finish(err)
+	}
+	return m, err
+}
+
+func (cs *clientStream) Trailer() metadata.MD {
+	// On RPC failure, we never need to retry, because usage requires that
+	// RecvMsg() returned a non-nil error before calling this function is valid.
+	// We would have retried earlier if necessary.
+	//
+	// Commit the attempt anyway, just in case users are not following those
+	// directions -- it will prevent races and should not meaningfully impact
+	// performance.
+	cs.commitAttempt()
+	if cs.attempt.s == nil {
+		return nil
+	}
+	return cs.attempt.s.Trailer()
+}
+
+func (cs *clientStream) replayBufferLocked() error {
+	a := cs.attempt
+	for _, f := range cs.buffer {
+		if err := f(a); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (cs *clientStream) bufferForRetryLocked(sz int, op func(a *csAttempt) error) {
+	// Note: we still will buffer if retry is disabled (for transparent retries).
+	if cs.committed {
+		return
+	}
+	cs.bufferSize += sz
+	if cs.bufferSize > cs.callInfo.maxRetryRPCBufferSize {
+		cs.commitAttemptLocked()
+		return
+	}
+	cs.buffer = append(cs.buffer, op)
+}
+
+func (cs *clientStream) SendMsg(m interface{}) (err error) {
+	defer func() {
+		if err != nil && err != io.EOF {
+			// Call finish on the client stream for errors generated by this SendMsg
+			// call, as these indicate problems created by this client.  (Transport
+			// errors are converted to an io.EOF error in csAttempt.sendMsg; the real
+			// error will be returned from RecvMsg eventually in that case, or be
+			// retried.)
+			cs.finish(err)
+		}
+	}()
+	if cs.sentLast {
+		return status.Errorf(codes.Internal, "SendMsg called after CloseSend")
+	}
+	if !cs.desc.ClientStreams {
+		cs.sentLast = true
+	}
+	data, err := encode(cs.codec, m)
+	if err != nil {
+		return err
+	}
+	compData, err := compress(data, cs.cp, cs.comp)
+	if err != nil {
+		return err
+	}
+	hdr, payload := msgHeader(data, compData)
+	// TODO(dfawley): should we be checking len(data) instead?
+	if len(payload) > *cs.callInfo.maxSendMessageSize {
+		return status.Errorf(codes.ResourceExhausted, "trying to send message larger than max (%d vs. %d)", len(payload), *cs.callInfo.maxSendMessageSize)
+	}
+	op := func(a *csAttempt) error {
+		err := a.sendMsg(m, hdr, payload, data)
+		// nil out the message and uncomp when replaying; they are only needed for
+		// stats which is disabled for subsequent attempts.
+		m, data = nil, nil
+		return err
+	}
+	return cs.withRetry(op, func() { cs.bufferForRetryLocked(len(hdr)+len(payload), op) })
+}
+
+func (cs *clientStream) RecvMsg(m interface{}) error {
+	err := cs.withRetry(func(a *csAttempt) error {
+		return a.recvMsg(m)
+	}, cs.commitAttemptLocked)
+	if err != nil || !cs.desc.ServerStreams {
+		// err != nil or non-server-streaming indicates end of stream.
+		cs.finish(err)
+	}
+	return err
+}
+
+func (cs *clientStream) CloseSend() error {
+	if cs.sentLast {
+		// TODO: return an error and finish the stream instead, due to API misuse?
+		return nil
+	}
+	cs.sentLast = true
+	op := func(a *csAttempt) error {
+		a.t.Write(a.s, nil, nil, &transport.Options{Last: true})
+		// Always return nil; io.EOF is the only error that might make sense
+		// instead, but there is no need to signal the client to call RecvMsg
+		// as the only use left for the stream after CloseSend is to call
+		// RecvMsg.  This also matches historical behavior.
+		return nil
+	}
+	cs.withRetry(op, func() { cs.bufferForRetryLocked(0, op) })
+	// We never returned an error here for reasons.
+	return nil
+}
+
+func (cs *clientStream) finish(err error) {
+	if err == io.EOF {
+		// Ending a stream with EOF indicates a success.
+		err = nil
+	}
+	cs.mu.Lock()
+	if cs.finished {
+		cs.mu.Unlock()
+		return
+	}
+	cs.finished = true
+	cs.commitAttemptLocked()
+	cs.mu.Unlock()
+	if err == nil {
+		cs.retryThrottler.successfulRPC()
+	}
+	if channelz.IsOn() {
+		if err != nil {
+			cs.cc.incrCallsFailed()
+		} else {
+			cs.cc.incrCallsSucceeded()
+		}
+	}
+	if cs.attempt != nil {
+		cs.attempt.finish(err)
+	}
+	// after functions all rely upon having a stream.
+	if cs.attempt.s != nil {
+		for _, o := range cs.opts {
+			o.after(cs.callInfo)
+		}
+	}
+	cs.cancel()
+}
+
+func (a *csAttempt) sendMsg(m interface{}, hdr, payld, data []byte) error {
+	cs := a.cs
+	if EnableTracing {
+		a.mu.Lock()
+		if a.trInfo.tr != nil {
+			a.trInfo.tr.LazyLog(&payload{sent: true, msg: m}, true)
+		}
+		a.mu.Unlock()
+	}
+	if err := a.t.Write(a.s, hdr, payld, &transport.Options{Last: !cs.desc.ClientStreams}); err != nil {
+		if !cs.desc.ClientStreams {
+			// For non-client-streaming RPCs, we return nil instead of EOF on error
+			// because the generated code requires it.  finish is not called; RecvMsg()
+			// will call it with the stream's status independently.
+			return nil
+		}
+		return io.EOF
+	}
+	if a.statsHandler != nil {
+		a.statsHandler.HandleRPC(cs.ctx, outPayload(true, m, data, payld, time.Now()))
+	}
+	if channelz.IsOn() {
+		a.t.IncrMsgSent()
+	}
+	return nil
+}
+
+func (a *csAttempt) recvMsg(m interface{}) (err error) {
+	cs := a.cs
+	var inPayload *stats.InPayload
+	if a.statsHandler != nil {
+		inPayload = &stats.InPayload{
+			Client: true,
+		}
+	}
+	if !a.decompSet {
+		// Block until we receive headers containing received message encoding.
+		if ct := a.s.RecvCompress(); ct != "" && ct != encoding.Identity {
+			if a.dc == nil || a.dc.Type() != ct {
+				// No configured decompressor, or it does not match the incoming
+				// message encoding; attempt to find a registered compressor that does.
+				a.dc = nil
+				a.decomp = encoding.GetCompressor(ct)
+			}
+		} else {
+			// No compression is used; disable our decompressor.
+			a.dc = nil
+		}
+		// Only initialize this state once per stream.
+		a.decompSet = true
+	}
+	err = recv(a.p, cs.codec, a.s, a.dc, m, *cs.callInfo.maxReceiveMessageSize, inPayload, a.decomp)
+	if err != nil {
+		if err == io.EOF {
+			if statusErr := a.s.Status().Err(); statusErr != nil {
+				return statusErr
+			}
+			return io.EOF // indicates successful end of stream.
+		}
+		return toRPCErr(err)
+	}
+	if EnableTracing {
+		a.mu.Lock()
+		if a.trInfo.tr != nil {
+			a.trInfo.tr.LazyLog(&payload{sent: false, msg: m}, true)
+		}
+		a.mu.Unlock()
+	}
+	if inPayload != nil {
+		a.statsHandler.HandleRPC(cs.ctx, inPayload)
+	}
+	if channelz.IsOn() {
+		a.t.IncrMsgRecv()
+	}
+	if cs.desc.ServerStreams {
+		// Subsequent messages should be received by subsequent RecvMsg calls.
+		return nil
+	}
+
+	// Special handling for non-server-stream rpcs.
+	// This recv expects EOF or errors, so we don't collect inPayload.
+	err = recv(a.p, cs.codec, a.s, a.dc, m, *cs.callInfo.maxReceiveMessageSize, nil, a.decomp)
+	if err == nil {
+		return toRPCErr(errors.New("grpc: client streaming protocol violation: get <nil>, want <EOF>"))
+	}
+	if err == io.EOF {
+		return a.s.Status().Err() // non-server streaming Recv returns nil on success
+	}
+	return toRPCErr(err)
+}
+
+func (a *csAttempt) finish(err error) {
+	a.mu.Lock()
+	if a.finished {
+		a.mu.Unlock()
+		return
+	}
+	a.finished = true
+	if err == io.EOF {
+		// Ending a stream with EOF indicates a success.
+		err = nil
+	}
+	if a.s != nil {
+		a.t.CloseStream(a.s, err)
+	}
+
+	if a.done != nil {
+		br := false
+		var tr metadata.MD
+		if a.s != nil {
+			br = a.s.BytesReceived()
+			tr = a.s.Trailer()
+		}
+		a.done(balancer.DoneInfo{
+			Err:           err,
+			Trailer:       tr,
+			BytesSent:     a.s != nil,
+			BytesReceived: br,
+		})
+	}
+	if a.statsHandler != nil {
+		end := &stats.End{
+			Client:    true,
+			BeginTime: a.cs.beginTime,
+			EndTime:   time.Now(),
+			Error:     err,
+		}
+		a.statsHandler.HandleRPC(a.cs.ctx, end)
+	}
+	if a.trInfo.tr != nil {
+		if err == nil {
+			a.trInfo.tr.LazyPrintf("RPC: [OK]")
+		} else {
+			a.trInfo.tr.LazyPrintf("RPC: [%v]", err)
+			a.trInfo.tr.SetError()
+		}
+		a.trInfo.tr.Finish()
+		a.trInfo.tr = nil
+	}
+	a.mu.Unlock()
+}
+
+// ServerStream defines the server-side behavior of a streaming RPC.
+//
+// All errors returned from ServerStream methods are compatible with the
+// status package.
+type ServerStream interface {
+	// SetHeader sets the header metadata. It may be called multiple times.
+	// When call multiple times, all the provided metadata will be merged.
+	// All the metadata will be sent out when one of the following happens:
+	//  - ServerStream.SendHeader() is called;
+	//  - The first response is sent out;
+	//  - An RPC status is sent out (error or success).
+	SetHeader(metadata.MD) error
+	// SendHeader sends the header metadata.
+	// The provided md and headers set by SetHeader() will be sent.
+	// It fails if called multiple times.
+	SendHeader(metadata.MD) error
+	// SetTrailer sets the trailer metadata which will be sent with the RPC status.
+	// When called more than once, all the provided metadata will be merged.
+	SetTrailer(metadata.MD)
+	// Context returns the context for this stream.
+	Context() context.Context
+	// SendMsg sends a message. On error, SendMsg aborts the stream and the
+	// error is returned directly.
+	//
+	// SendMsg blocks until:
+	//   - There is sufficient flow control to schedule m with the transport, or
+	//   - The stream is done, or
+	//   - The stream breaks.
+	//
+	// SendMsg does not wait until the message is received by the client. An
+	// untimely stream closure may result in lost messages.
+	//
+	// It is safe to have a goroutine calling SendMsg and another goroutine
+	// calling RecvMsg on the same stream at the same time, but it is not safe
+	// to call SendMsg on the same stream in different goroutines.
+	SendMsg(m interface{}) error
+	// RecvMsg blocks until it receives a message into m or the stream is
+	// done. It returns io.EOF when the client has performed a CloseSend. On
+	// any non-EOF error, the stream is aborted and the error contains the
+	// RPC status.
+	//
+	// It is safe to have a goroutine calling SendMsg and another goroutine
+	// calling RecvMsg on the same stream at the same time, but it is not
+	// safe to call RecvMsg on the same stream in different goroutines.
+	RecvMsg(m interface{}) error
+}
+
+// serverStream implements a server side Stream.
+type serverStream struct {
+	ctx   context.Context
+	t     transport.ServerTransport
+	s     *transport.Stream
+	p     *parser
+	codec baseCodec
+
+	cp     Compressor
+	dc     Decompressor
+	comp   encoding.Compressor
+	decomp encoding.Compressor
+
+	maxReceiveMessageSize int
+	maxSendMessageSize    int
+	trInfo                *traceInfo
+
+	statsHandler stats.Handler
+
+	mu sync.Mutex // protects trInfo.tr after the service handler runs.
+}
+
+func (ss *serverStream) Context() context.Context {
+	return ss.ctx
+}
+
+func (ss *serverStream) SetHeader(md metadata.MD) error {
+	if md.Len() == 0 {
+		return nil
+	}
+	return ss.s.SetHeader(md)
+}
+
+func (ss *serverStream) SendHeader(md metadata.MD) error {
+	return ss.t.WriteHeader(ss.s, md)
+}
+
+func (ss *serverStream) SetTrailer(md metadata.MD) {
+	if md.Len() == 0 {
+		return
+	}
+	ss.s.SetTrailer(md)
+}
+
+func (ss *serverStream) SendMsg(m interface{}) (err error) {
+	defer func() {
+		if ss.trInfo != nil {
+			ss.mu.Lock()
+			if ss.trInfo.tr != nil {
+				if err == nil {
+					ss.trInfo.tr.LazyLog(&payload{sent: true, msg: m}, true)
+				} else {
+					ss.trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+					ss.trInfo.tr.SetError()
+				}
+			}
+			ss.mu.Unlock()
+		}
+		if err != nil && err != io.EOF {
+			st, _ := status.FromError(toRPCErr(err))
+			ss.t.WriteStatus(ss.s, st)
+		}
+		if channelz.IsOn() && err == nil {
+			ss.t.IncrMsgSent()
+		}
+	}()
+	data, err := encode(ss.codec, m)
+	if err != nil {
+		return err
+	}
+	compData, err := compress(data, ss.cp, ss.comp)
+	if err != nil {
+		return err
+	}
+	hdr, payload := msgHeader(data, compData)
+	// TODO(dfawley): should we be checking len(data) instead?
+	if len(payload) > ss.maxSendMessageSize {
+		return status.Errorf(codes.ResourceExhausted, "trying to send message larger than max (%d vs. %d)", len(payload), ss.maxSendMessageSize)
+	}
+	if err := ss.t.Write(ss.s, hdr, payload, &transport.Options{Last: false}); err != nil {
+		return toRPCErr(err)
+	}
+	if ss.statsHandler != nil {
+		ss.statsHandler.HandleRPC(ss.s.Context(), outPayload(false, m, data, payload, time.Now()))
+	}
+	return nil
+}
+
+func (ss *serverStream) RecvMsg(m interface{}) (err error) {
+	defer func() {
+		if ss.trInfo != nil {
+			ss.mu.Lock()
+			if ss.trInfo.tr != nil {
+				if err == nil {
+					ss.trInfo.tr.LazyLog(&payload{sent: false, msg: m}, true)
+				} else if err != io.EOF {
+					ss.trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+					ss.trInfo.tr.SetError()
+				}
+			}
+			ss.mu.Unlock()
+		}
+		if err != nil && err != io.EOF {
+			st, _ := status.FromError(toRPCErr(err))
+			ss.t.WriteStatus(ss.s, st)
+		}
+		if channelz.IsOn() && err == nil {
+			ss.t.IncrMsgRecv()
+		}
+	}()
+	var inPayload *stats.InPayload
+	if ss.statsHandler != nil {
+		inPayload = &stats.InPayload{}
+	}
+	if err := recv(ss.p, ss.codec, ss.s, ss.dc, m, ss.maxReceiveMessageSize, inPayload, ss.decomp); err != nil {
+		if err == io.EOF {
+			return err
+		}
+		if err == io.ErrUnexpectedEOF {
+			err = status.Errorf(codes.Internal, io.ErrUnexpectedEOF.Error())
+		}
+		return toRPCErr(err)
+	}
+	if inPayload != nil {
+		ss.statsHandler.HandleRPC(ss.s.Context(), inPayload)
+	}
+	return nil
+}
+
+// MethodFromServerStream returns the method string for the input stream.
+// The returned string is in the format of "/service/method".
+func MethodFromServerStream(stream ServerStream) (string, bool) {
+	return Method(stream.Context())
+}
diff --git a/go/vendor/google.golang.org/grpc/tap/tap.go b/go/vendor/google.golang.org/grpc/tap/tap.go
new file mode 100644
index 0000000..22b8fb5
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/tap/tap.go
@@ -0,0 +1,51 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package tap defines the function handles which are executed on the transport
+// layer of gRPC-Go and related information. Everything here is EXPERIMENTAL.
+package tap
+
+import (
+	"golang.org/x/net/context"
+)
+
+// Info defines the relevant information needed by the handles.
+type Info struct {
+	// FullMethodName is the string of grpc method (in the format of
+	// /package.service/method).
+	FullMethodName string
+	// TODO: More to be added.
+}
+
+// ServerInHandle defines the function which runs before a new stream is created
+// on the server side. If it returns a non-nil error, the stream will not be
+// created and a RST_STREAM will be sent back to the client with REFUSED_STREAM.
+// The client will receive an RPC error "code = Unavailable, desc = stream
+// terminated by RST_STREAM with error code: REFUSED_STREAM".
+//
+// It's intended to be used in situations where you don't want to waste the
+// resources to accept the new stream (e.g. rate-limiting). And the content of
+// the error will be ignored and won't be sent back to the client. For other
+// general usages, please use interceptors.
+//
+// Note that it is executed in the per-connection I/O goroutine(s) instead of
+// per-RPC goroutine. Therefore, users should NOT have any
+// blocking/time-consuming work in this handle. Otherwise all the RPCs would
+// slow down. Also, for the same reason, this handle won't be called
+// concurrently by gRPC.
+type ServerInHandle func(ctx context.Context, info *Info) (context.Context, error)
diff --git a/go/vendor/google.golang.org/grpc/trace.go b/go/vendor/google.golang.org/grpc/trace.go
new file mode 100644
index 0000000..c1c96de
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/trace.go
@@ -0,0 +1,113 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+	"time"
+
+	"golang.org/x/net/trace"
+)
+
+// EnableTracing controls whether to trace RPCs using the golang.org/x/net/trace package.
+// This should only be set before any RPCs are sent or received by this program.
+var EnableTracing bool
+
+// methodFamily returns the trace family for the given method.
+// It turns "/pkg.Service/GetFoo" into "pkg.Service".
+func methodFamily(m string) string {
+	m = strings.TrimPrefix(m, "/") // remove leading slash
+	if i := strings.Index(m, "/"); i >= 0 {
+		m = m[:i] // remove everything from second slash
+	}
+	if i := strings.LastIndex(m, "."); i >= 0 {
+		m = m[i+1:] // cut down to last dotted component
+	}
+	return m
+}
+
+// traceInfo contains tracing information for an RPC.
+type traceInfo struct {
+	tr        trace.Trace
+	firstLine firstLine
+}
+
+// firstLine is the first line of an RPC trace.
+type firstLine struct {
+	client     bool // whether this is a client (outgoing) RPC
+	remoteAddr net.Addr
+	deadline   time.Duration // may be zero
+}
+
+func (f *firstLine) String() string {
+	var line bytes.Buffer
+	io.WriteString(&line, "RPC: ")
+	if f.client {
+		io.WriteString(&line, "to")
+	} else {
+		io.WriteString(&line, "from")
+	}
+	fmt.Fprintf(&line, " %v deadline:", f.remoteAddr)
+	if f.deadline != 0 {
+		fmt.Fprint(&line, f.deadline)
+	} else {
+		io.WriteString(&line, "none")
+	}
+	return line.String()
+}
+
+const truncateSize = 100
+
+func truncate(x string, l int) string {
+	if l > len(x) {
+		return x
+	}
+	return x[:l]
+}
+
+// payload represents an RPC request or response payload.
+type payload struct {
+	sent bool        // whether this is an outgoing payload
+	msg  interface{} // e.g. a proto.Message
+	// TODO(dsymonds): add stringifying info to codec, and limit how much we hold here?
+}
+
+func (p payload) String() string {
+	if p.sent {
+		return truncate(fmt.Sprintf("sent: %v", p.msg), truncateSize)
+	}
+	return truncate(fmt.Sprintf("recv: %v", p.msg), truncateSize)
+}
+
+type fmtStringer struct {
+	format string
+	a      []interface{}
+}
+
+func (f *fmtStringer) String() string {
+	return fmt.Sprintf(f.format, f.a...)
+}
+
+type stringer string
+
+func (s stringer) String() string { return string(s) }
diff --git a/go/vendor/google.golang.org/grpc/version.go b/go/vendor/google.golang.org/grpc/version.go
new file mode 100644
index 0000000..d8e0287
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/version.go
@@ -0,0 +1,22 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+// Version is the current grpc version.
+const Version = "1.16.0"
diff --git a/go/vendor/google.golang.org/grpc/vet.sh b/go/vendor/google.golang.org/grpc/vet.sh
new file mode 100755
index 0000000..eb32870
--- /dev/null
+++ b/go/vendor/google.golang.org/grpc/vet.sh
@@ -0,0 +1,129 @@
+#!/bin/bash
+
+if [[ `uname -a` = *"Darwin"* ]]; then
+  echo "It seems you are running on Mac. This script does not work on Mac. See https://github.com/grpc/grpc-go/issues/2047"
+  exit 1
+fi
+
+set -ex  # Exit on error; debugging enabled.
+set -o pipefail  # Fail a pipe if any sub-command fails.
+
+die() {
+  echo "$@" >&2
+  exit 1
+}
+
+# Check to make sure it's safe to modify the user's git repo.
+if git status --porcelain | read; then
+  die "Uncommitted or untracked files found; commit changes first"
+fi
+
+if [[ -d "${GOPATH}/src" ]]; then
+  die "\${GOPATH}/src (${GOPATH}/src) exists; this script will delete it."
+fi
+
+# Undo any edits made by this script.
+cleanup() {
+  rm -rf "${GOPATH}/src"
+  git reset --hard HEAD
+}
+trap cleanup EXIT
+
+PATH="${GOPATH}/bin:${GOROOT}/bin:${PATH}"
+
+if [[ "$1" = "-install" ]]; then
+  # Check for module support
+  if go help mod >& /dev/null; then
+    go install \
+      github.com/golang/lint/golint \
+      golang.org/x/tools/cmd/goimports \
+      honnef.co/go/tools/cmd/staticcheck \
+      github.com/client9/misspell/cmd/misspell \
+      github.com/golang/protobuf/protoc-gen-go
+  else
+    # Ye olde `go get` incantation.
+    # Note: this gets the latest version of all tools (vs. the pinned versions
+    # with Go modules).
+    go get -u \
+      github.com/golang/lint/golint \
+      golang.org/x/tools/cmd/goimports \
+      honnef.co/go/tools/cmd/staticcheck \
+      github.com/client9/misspell/cmd/misspell \
+      github.com/golang/protobuf/protoc-gen-go
+  fi
+  if [[ -z "${VET_SKIP_PROTO}" ]]; then
+    if [[ "${TRAVIS}" = "true" ]]; then
+      PROTOBUF_VERSION=3.3.0
+      PROTOC_FILENAME=protoc-${PROTOBUF_VERSION}-linux-x86_64.zip
+      pushd /home/travis
+      wget https://github.com/google/protobuf/releases/download/v${PROTOBUF_VERSION}/${PROTOC_FILENAME}
+      unzip ${PROTOC_FILENAME}
+      bin/protoc --version
+      popd
+    elif ! which protoc > /dev/null; then
+      die "Please install protoc into your path"
+    fi
+  fi
+  exit 0
+elif [[ "$#" -ne 0 ]]; then
+  die "Unknown argument(s): $*"
+fi
+
+git ls-files "*.go" | xargs grep -L "\(Copyright [0-9]\{4,\} gRPC authors\)\|DO NOT EDIT" 2>&1 | tee /dev/stderr | (! read)
+git ls-files "*.go" | xargs grep -l '"math/rand"' 2>&1 | (! grep -v '^examples\|^stress\|grpcrand') | tee /dev/stderr | (! read)
+git ls-files | xargs dirname | sort | uniq | xargs go run test/go_vet/vet.go | tee /dev/stderr | (! read)
+gofmt -s -d -l . 2>&1 | tee /dev/stderr | (! read)
+goimports -l . 2>&1 | tee /dev/stderr | (! read)
+golint ./... 2>&1 | (grep -vE "(_mock|\.pb)\.go:" || true) | tee /dev/stderr | (! read)
+
+# Rewrite golang.org/x/net/context -> context imports (see grpc/grpc-go#1484).
+# TODO: Remove this mangling once "context" is imported directly (grpc/grpc-go#711).
+git ls-files "*.go" | xargs sed -i 's:"golang.org/x/net/context":"context":'
+set +o pipefail # vet exits with non-zero error if issues are found
+
+# TODO(deklerk) remove when we drop Go 1.6 support
+go tool vet -all . 2>&1 | \
+    grep -vE 'clientconn.go:.*cancel (function|var)' | \
+    grep -vE '.*transport_test.go:.*cancel' | \
+    tee /dev/stderr | \
+    (! read)
+
+set -o pipefail
+git reset --hard HEAD
+
+if [[ -z "${VET_SKIP_PROTO}" ]]; then
+  PATH="/home/travis/bin:${PATH}" make proto && \
+    git status --porcelain 2>&1 | (! read) || \
+    (git status; git --no-pager diff; exit 1)
+fi
+
+if go help mod >& /dev/null; then
+  go mod tidy && \
+    git status --porcelain 2>&1 | (! read) || \
+    (git status; git --no-pager diff; exit 1)
+fi
+
+### HACK HACK HACK: Remove once staticcheck works with modules.
+# Make a symlink in ${GOPATH}/src to its ${GOPATH}/pkg/mod equivalent for every package we use.
+for x in $(find "${GOPATH}/pkg/mod" -name '*@*' | grep -v \/mod\/cache\/); do
+  pkg="$(echo ${x#"${GOPATH}/pkg/mod/"} | cut -f1 -d@)";
+  # If multiple versions exist, just use the existing one.
+  if [[ -L "${GOPATH}/src/${pkg}" ]]; then continue; fi
+  mkdir -p "$(dirname "${GOPATH}/src/${pkg}")";
+  ln -s $x "${GOPATH}/src/${pkg}";
+done
+### END HACK HACK HACK
+
+# TODO(menghanl): fix errors in transport_test.
+staticcheck -ignore '
+internal/transport/transport_test.go:SA2002
+benchmark/benchmain/main.go:SA1019
+stats/stats_test.go:SA1019
+test/end2end_test.go:SA1019
+balancer_test.go:SA1019
+balancer.go:SA1019
+clientconn_test.go:SA1019
+internal/transport/handler_server_test.go:SA1019
+internal/transport/handler_server.go:SA1019
+' ./...
+misspell -error .