/
ctrl.go
170 lines (147 loc) · 3.28 KB
/
ctrl.go
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package chief
import (
"context"
"log"
"sync"
clientv3 "go.etcd.io/etcd/client/v3"
"go.etcd.io/etcd/client/v3/concurrency"
)
type leaderCtrl struct {
mu sync.Mutex
registeredWorkers []Worker
runningWorkers []Worker
isLeader bool
wg *sync.WaitGroup
ctx context.Context
ctxCancel context.CancelFunc
etcdCli *clientv3.Client
token string
}
// NewController returns a new Controller from etcd client.
//
// It runs worker goroutine that should be stopped using Controller.Stop
// method.
//
// token is a unique identifier of election participants group. Only one
// of participants would be elected in a group, identified by token
// on current etcd cluster.
func NewController(cli *clientv3.Client, token string) Controller {
lc := &leaderCtrl{
wg: &sync.WaitGroup{},
etcdCli: cli,
token: token,
}
lc.ctx, lc.ctxCancel = context.WithCancel(context.Background())
lc.wg.Add(1)
go lc.worker()
return lc
}
func (ctrl *leaderCtrl) Register(worker Worker) {
ctrl.mu.Lock()
defer ctrl.mu.Unlock()
ctrl.registeredWorkers = append(ctrl.registeredWorkers, worker)
if ctrl.isLeader {
worker.Start()
ctrl.runningWorkers = append(ctrl.runningWorkers, worker)
}
}
func (ctrl *leaderCtrl) startAll() {
ctrl.mu.Lock()
defer ctrl.mu.Unlock()
if ctrl.isLeader {
return
}
for _, w := range ctrl.registeredWorkers {
w.Start()
ctrl.runningWorkers = append(ctrl.runningWorkers, w)
}
ctrl.isLeader = true
}
func (ctrl *leaderCtrl) stopAll() {
ctrl.mu.Lock()
defer ctrl.mu.Unlock()
if !ctrl.isLeader {
return
}
for _, w := range ctrl.runningWorkers {
w.Stop()
}
ctrl.runningWorkers = ctrl.runningWorkers[:0]
ctrl.isLeader = false
}
func workerSession(ctx context.Context, cli *clientv3.Client, ctrl *leaderCtrl) error {
// In case of closing, we need a way to interrupt NewSession creation when
// etcd cluster is broken
sctx, scancel := context.WithCancel(cli.Ctx())
newSessionDoneCh := make(chan struct{})
// goroutine to monitor session closing
go func() {
select {
case <-newSessionDoneCh:
case <-ctx.Done():
scancel()
}
}()
sess, err := concurrency.NewSession(
cli,
concurrency.WithTTL(10),
concurrency.WithContext(sctx),
)
close(newSessionDoneCh)
if err != nil {
return err
}
defer func() {
if err := sess.Close(); err != nil {
log.Printf("session closed with error: %+v", err)
}
scancel()
}()
// Notify session done
go func() {
<-sess.Done()
log.Print("session done watcher")
}()
election := concurrency.NewElection(sess, ctrl.token)
err = election.Campaign(ctx, "")
if err != nil {
return err
}
// Ensure session is active before running registered workers
select {
case <-ctx.Done():
return ctx.Err()
case <-sess.Done():
return nil
default:
}
ctrl.startAll()
defer func() {
ctrl.stopAll()
}()
select {
case <-ctx.Done():
return ctx.Err()
case <-sess.Done():
return nil
}
}
func (ctrl *leaderCtrl) worker() {
defer ctrl.wg.Done()
for {
err := workerSession(ctrl.ctx, ctrl.etcdCli, ctrl)
if err != nil {
log.Printf("worker error: %+v", err)
}
// Exit on context closed
select {
case <-ctrl.ctx.Done():
return
default:
}
}
}
func (ctrl *leaderCtrl) Close() {
ctrl.ctxCancel()
ctrl.wg.Wait()
}