hswaw/laserproxy/locker.go

package main

import (
	"context"
	"time"

	"github.com/golang/glog"
)

type lockCtrl struct {
	getCurrent *lockCtrlGetCurrent
	take *lockCtrlTake
	release *lockCtrlRelease
	subscribe *lockCtrlSubscribe
	bump *lockCtrlBump
}

type lockCtrlGetCurrent struct {
	res chan *lockResCurrent
}

type lockCtrlTake struct {
	note string
	addr string
	prev string
	res chan bool
}

type lockCtrlRelease struct {
	addr string
	force bool
	res chan struct{}
}

type lockCtrlSubscribe struct {
	subscriber chan *lockUpdate
}

type lockCtrlBump struct {
	addr string
}

type lockResCurrent struct {
	note string
	addr string
	deadline time.Time
}

type lockUpdate struct {
	note string
	addr string
}

func (s *service) runLocker(ctx context.Context, ctrlC chan *lockCtrl, ownershipDuration time.Duration) {
	glog.Infof("Locker starting...")

	var curNote string
	var curAddr string
	var curDeadline time.Time
	var subscribers []chan *lockUpdate

	notify := func() {
		for _, sub := range subscribers {
			go func() {
				sub <- &lockUpdate{
					note: curNote,
					addr: curAddr,
				}
			}()
		}
	}

	t := time.NewTicker(5 * time.Second)
	defer t.Stop()

	for {
		select {
		case <-ctx.Done():
			err := ctx.Err()
			glog.Errorf("Locker stoppped: %v", err)
			return
		case <-t.C:
			if curAddr != "" && time.Now().After(curDeadline) {
				glog.Infof("Expiring lock")
				curAddr = ""
				curNote = ""
				notify()
			}
		case ctrl := <-ctrlC:
			switch {
			case ctrl.take != nil:
				won := false
				if curAddr == ctrl.take.prev {
					won = true
					curNote = ctrl.take.note
					curAddr = ctrl.take.addr
					curDeadline = time.Now().Add(ownershipDuration)
					notify()
					glog.Infof("Lock taken by %q %q", curNote, curAddr)
				}
				go func() {
					ctrl.take.res <- won
				}()
			case ctrl.release != nil:
				if curAddr == ctrl.release.addr || ctrl.release.force {
					curAddr = ""
					curNote = ""
					notify()
					glog.Infof("Lock relased")
				}
				go func() {
					ctrl.release.res <- struct{}{}
				}()
			case ctrl.getCurrent != nil:
				go func() {
					ctrl.getCurrent.res <- &lockResCurrent{
						note: curNote,
						addr: curAddr,
						deadline: curDeadline,
					}
				}()
			case ctrl.bump != nil:
				if curAddr != "" {
					curDeadline = time.Now().Add(ownershipDuration)
				}
			case ctrl.subscribe != nil:
				subscribers = append(subscribers, ctrl.subscribe.subscriber)
			}
		}
	}
}