Discovery.Manager: close sync ch after sender() is stopped (#14465)

* close sync ch after sender() is stopped
* break if chan is closed

Signed-off-by: liyandi <littlepangdi@163.com>
Co-authored-by: liyandi <liyandi@xiaomi.com>

discovery/manager.go

@@ -365,8 +365,10 @@ func (m *Manager) updater(ctx context.Context, p *Provider, updates chan []*targ
 
 func (m *Manager) sender() {
 	ticker := time.NewTicker(m.updatert)
-	defer ticker.Stop()
-
+	defer func() {
+		ticker.Stop()
+		close(m.syncCh)
+	}()
 	for {
 		select {
 		case <-m.ctx.Done():

notifier/manager.go

@@ -254,7 +254,10 @@ func (n *Manager) targetUpdateLoop(tsets <-chan map[string][]*targetgroup.Group)
 			select {
 			case <-n.stopRequested:
 				return
-			case ts := <-tsets:
+			case ts, ok := <-tsets:
+				if !ok {
+					break
+				}
 				n.reload(ts)
 			}
 		}

scrape/manager.go

@@ -127,7 +127,10 @@ func (m *Manager) Run(tsets <-chan map[string][]*targetgroup.Group) error {
 	go m.reloader()
 	for {
 		select {
-		case ts := <-tsets:
+		case ts, ok := <-tsets:
+			if !ok {
+				break
+			}
 			m.updateTsets(ts)
 
 			select {