feat: etcd-election support wait

providers/etcd-election/election.go

@@ -74,11 +74,13 @@ type Interface interface {
 	ResignLeader() error
 	OnLeader(handler func(context.Context))
 	Watch(ctx context.Context, opts ...WatchOption) <-chan Event
+	ResetWait(wait bool) // `true` means waiting participate in election until wait become `false`
 }
 
 type config struct {
 	Prefix string `file:"root_path" default:"etcd-election"`
 	NodeID string `file:"node_id"`
+	Wait   bool   `file:"wait" default:"false"`
 }
 
 type provider struct {
@@ -87,6 +89,10 @@ type provider struct {
 	Client *clientv3.Client `autowired:"etcd-client"`
 	prefix string
 
+	wait          bool
+	stopWaitChan  chan struct{}
+	beginWaitChan chan struct{}
+
 	lock           sync.RWMutex
 	leaderHandlers []func(ctx context.Context)
 	cancelHandler  func()
@@ -102,18 +108,35 @@ func (p *provider) Init(ctx servicehub.Context) error {
 	if len(p.Cfg.NodeID) <= 0 {
 		p.Cfg.NodeID = uuid.NewV4().String()
 	}
+	p.wait = p.Cfg.Wait
+	p.beginWaitChan = make(chan struct{})
+	p.stopWaitChan = make(chan struct{})
 	p.Log.Info("my node id: ", p.Cfg.NodeID)
 	return nil
 }
 
-func (p *provider) reset(session *concurrency.Session) {
+func (p *provider) resetSession(session *concurrency.Session) {
 	session.Close()
 	p.lock.Lock()
 	p.session, p.election = nil, nil
 	p.iAmLeader = false
 	p.lock.Unlock()
 }
 
+func (p *provider) ResetWait(wait bool) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	if wait == p.wait {
+		return
+	}
+	p.wait = wait
+	if !p.wait {
+		p.stopWaitChan <- struct{}{}
+	} else {
+		p.beginWaitChan <- struct{}{}
+	}
+}
+
 func (p *provider) Run(ctx context.Context) error {
 	for {
 		select {
@@ -122,6 +145,15 @@ func (p *provider) Run(ctx context.Context) error {
 		default:
 		}
 
+		p.lock.Lock()
+		wait := p.wait
+		p.lock.Unlock()
+
+		if wait {
+			p.Log.Info("waiting participate in election until wait is false")
+			<-p.stopWaitChan
+		}
+
 		session, err := p.newSession(ctx, 5*time.Second)
 		if err != nil {
 			if errors.Is(err, context.Canceled) {
@@ -140,7 +172,7 @@ func (p *provider) Run(ctx context.Context) error {
 			if errors.Is(err, context.Canceled) {
 				return nil
 			}
-			p.reset(session)
+			p.resetSession(session)
 			p.Log.Errorf("fail to Campaign: %s", err, reflect.TypeOf(err))
 			time.Sleep(1 * time.Second)
 			continue
@@ -151,7 +183,7 @@ func (p *provider) Run(ctx context.Context) error {
 		// The campaign of B exited with nil after connection was restored.
 		select {
 		case <-session.Done():
-			p.reset(session)
+			p.resetSession(session)
 			continue
 		default:
 		}
@@ -166,6 +198,10 @@ func (p *provider) Run(ctx context.Context) error {
 		case <-ctx.Done():
 			p.resignLeader()
 			return nil
+		case <-p.beginWaitChan:
+			p.Log.Info("begin wait, exit election")
+			p.resignLeader()
+			continue
 		}
 	}
 }

providers/etcd-election/examples/examples.yaml

@@ -4,7 +4,8 @@ etcd:
         cert_file: "etcd-client.pem"
         cert_key_file: "etcd-client-key.pem"
         ca_file: "etcd-ca.pem"
-  
+
 example:
 
-etcd-election:
+etcd-election:
+    wait: true

providers/etcd-election/examples/main.go

@@ -51,13 +51,22 @@ func (p *provider) leaderTask(ctx context.Context) {
 }
 
 func (p *provider) Run(ctx context.Context) error {
-	select {
-	case <-time.After(10 * time.Second):
-		p.Log.Info("resign leader")
-		p.Election.ResignLeader()
-	case <-ctx.Done():
+	wait := true
+	ticker := time.NewTicker(5 * time.Second)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-time.After(10 * time.Second):
+			p.Log.Info("resign leader")
+			p.Election.ResignLeader()
+		case <-ticker.C:
+			wait = !wait
+			p.Log.Info("reset wait: ", wait)
+			p.Election.ResetWait(wait)
+		case <-ctx.Done():
+			return nil
+		}
 	}
-	return nil
 }
 
 func init() {