local kube = import "../../../kube/kube.libsonnet";

{
    // Cluster sets up all cluster-specific monitoring resources in their own namespace.
    //
    // Currently this consists of a prometheus server that scrapes k8s nodes for kubelet
    // and cAdvisor metrics, and possibly ships over metrics to the global tier via set
    // upstreams.
    Cluster(name):: {
        local cluster = self,
        local cfg = cluster.cfg,
        cfg:: {
            name: name,
            namespace: "monitoring-cluster",

            images: {
                prometheus: "prom/prometheus:v2.18.1",
            },

            storageClasses: {
                prometheus: error "storageClasses.prometheus must be set",
            },

            // Username used to authenticate to upstreams.
            username: error "username must be set",

            // Global tier upstreams that this cluster should ship metrics off to.
            // List of
            //  {
            //     remote: URL of upstream
            //     password: password used to authenticate, in conjunction with cfg.username.
            //  
            upstreams: [],
        },

        namespace: kube.Namespace(cfg.namespace),

        prometheus: {
            local prometheus = self,

            // Configuration that's going to be emitted as prometheus.yml and passed to the
            // prometheus server for this cluster.
            configuration:: {
                global: {
                    external_labels: {
                        cluster: cluster.cfg.name,
                    },
                },

                // Constructor for a Kubernetes scrape job that uses the pod's service account and
                // TLS configuration, selecting the given k8s scrape 'role'.
                local kubeScrapeConfig = function(name, role) {
                    job_name: name,
                    scheme: "https",
                    scrape_interval: "30s",
                    kubernetes_sd_configs: [ { role: role }, ],
                    tls_config: {
                        ca_file: "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt",
                    },
                    bearer_token_file: "/var/run/secrets/kubernetes.io/serviceaccount/token",
                },

                scrape_configs: [
                    // When scraping node-based metrics (ie. node and cadvisor metrics) we contact
                    // the metrics endpoints on the kubelet via the API server. This is done by
                    // relabeling _address__ and __metrics_path__ to point at the k8s API server,
                    // and at the API server proxy path to reach a node's metrics endpoint.
                    //
                    // This approach was lifted from the prometheus examples for Kubernetes, and
                    // while the benefits outlined there do not matter that much to us (our
                    // kubelets listen on public addresses, anyway), we still enjoy this approach
                    // for the fact that we don't have to hardcode the kubelet TLS port.
                    //
                    // https://github.com/prometheus/prometheus/blob/master/documentation/examples/prometheus-kubernetes.yml
                    //
                    // When contacting the API server, we hardcode the 'hswaw.net' DNS suffix as
                    // our API server's TLS certificate only has a CN/SAN for its full FQDN, not
                    // the .svc.cluster.local shorthand (see //cluster/clustercfg:clustercfg.py).

                    // Scrape Kubernetes node metrics via apiserver. This emites kube_node_* metrics.
                    kubeScrapeConfig("cluster_node_metrics", "node") {
                        relabel_configs: [
                            {
                                action: "labelmap",
                                regex: "__meta_kubernetes_node_label_(.+)",
                            },
                            {
                                action: "replace",
                                target_label: "__address__",
                                replacement: "kubernetes.default.svc.%s.hswaw.net:443" % [cluster.cfg.name],
                            },
                            {
                                target_label: "__metrics_path__",
                                source_labels: ["__meta_kubernetes_node_name"],
                                regex: "(.+)",
                                replacement: "/api/v1/nodes/${1}/proxy/metrics",
                            },
                        ],
                    },
                    // Scrape Kubernetes node cadvisor metrics via apiserver. This emits container_* metrics.
                    kubeScrapeConfig("cluster_cadvisor_metrics", "node") {
                        relabel_configs: [
                            {
                                action: "labelmap",
                                regex: "__meta_kubernetes_node_label_(.+)",
                            },
                            {
                                action: "replace",
                                target_label: "__address__",
                                replacement: "kubernetes.default.svc.%s.hswaw.net:443" % [cluster.cfg.name],
                            },
                            {
                                target_label: "__metrics_path__",
                                source_labels: ["__meta_kubernetes_node_name"],
                                regex: "(.+)",
                                replacement: "/api/v1/nodes/${1}/proxy/metrics/cadvisor",
                            },
                        ],
                    },
                ],

                remote_write: [
                    {
                        url: u.remote,
                        basic_auth: {
                            username: cluster.cfg.username,
                            password: u.password,
                        },
                    }
                    for u in cluster.cfg.upstreams
                ],
            },

            configmap: kube.ConfigMap("prometheus-cluster") {
                metadata+: {
                    namespace: cfg.namespace,
                },
                data: {
                    "prometheus.yml": std.manifestYamlDoc(prometheus.configuration),
                },
            },

            sa: kube.ServiceAccount("prometheus-cluster") {
                metadata+: {
                    namespace: cfg.namespace,
                },
            },

            cr: kube.ClusterRole("monitoring-cluster-prometheus-server-%s" % [cfg.name]) {
                rules: [
                    // Allow access to all metrics.
                    { nonResourceURLs: ["/metrics"], verbs: ["get"], },
                    // Allow to access node details for discovery.
                    { apiGroups: [""], resources: ["nodes"], verbs: ["list", "watch", "get"], },
                    // Allow to proxy to bare node HTTP to access per-node metrics endpoints. 
                    { apiGroups: [""], resources: ["nodes/proxy"], verbs: ["get"], },
                ],
            },

            crb: kube.ClusterRoleBinding("monitoring-cluster-prometheus-server-%s" % [cfg.name]) {
                subjects_: [prometheus.sa],
                roleRef_: prometheus.cr,
            },

            deploy: kube.Deployment("prometheus-cluster") {
                metadata+: {
                    namespace: cfg.namespace,
                },
                spec+: {
                    template+: {
                        spec+: {
                            containers_: {
                                default: kube.Container("default") {
                                    image: cfg.images.prometheus,
                                    command: [
                                        "/bin/prometheus",
                                        "--config.file=/etc/prometheus/prometheus.yml",
                                        "--storage.tsdb.path=/prometheus",
                                        "--storage.tsdb.retention.size=10GB",
                                        "--web.console.libraries=/usr/share/prometheus/console_libraries",
                                        "--web.console.templates=/usr/share/prometheus/consoles",
                                        "--web.enable-lifecycle",
                                    ],
                                    resources: {
                                        requests: {
                                            memory: "256Mi",
                                            cpu: "100m",
                                        },
                                        limits: {
                                            memory: "1Gi",
                                            cpu: "1",
                                        },
                                    },
                                    volumeMounts_: {
                                        data: { mountPath: "/prometheus", },
                                        configmap: { mountPath: "/etc/prometheus", },
                                    },
                                },
                            },
                            serviceAccountName: prometheus.sa.metadata.name,
                            tolerations: [
                                { key: "CriticalAddonsOnly", operator: "Exists" },
                            ],
                            volumes_: {
                                data: kube.PersistentVolumeClaimVolume(prometheus.pvc),
                                configmap: kube.ConfigMapVolume(prometheus.configmap),
                            },
                        },
                    },
                },
            },

            // Kubernetes metric storage volume.
            pvc: kube.PersistentVolumeClaim("prometheus-cluster") {
                metadata+: {
                    namespace: cfg.namespace,
                },
                spec+: {
                    storageClassName: cfg.storageClasses.prometheus,
                    accessModes: ["ReadWriteOnce"],
                    resources: {
                        requests: {
                            storage: "16Gi",
                        },
                    },
                },
            },

            // Network Policy governing access to the prometheus server.
            np: kube.NetworkPolicy("prometheus-cluster") {
                metadata+: {
                    namespace: cfg.namespace,
                },
                spec+: kube.podLabelsSelector(prometheus.deploy) {
                    ingress_: {
                        // Deny all inbound traffic to pod.
                        // This will be augmented to allow access from some other pod/namespace
                        // in the future.
                    },
                    egress_: {
                        // Allow all outbound traffic from pod.
                        outboundAll: {},
                    },
                    policyTypes: ["Ingress", "Egress"],
                },
            },
        },
    },
}