Correctly stop the timer used in the remote write path.

storage/remote/queue_manager.go

@@ -430,6 +430,14 @@ func (s *shards) runShard(i int) {
 	pendingSamples := model.Samples{}
 
 	timer := time.NewTimer(s.qm.cfg.BatchSendDeadline)
+	defer func() {
+		if !timer.Stop() {
+			select {
+			case <-timer.C:
+			default:
+			}
+		}
+	}()
 
 	for {
 		select {
@@ -449,11 +457,16 @@ func (s *shards) runShard(i int) {
 			for len(pendingSamples) >= s.qm.cfg.MaxSamplesPerSend {
 				s.sendSamples(pendingSamples[:s.qm.cfg.MaxSamplesPerSend])
 				pendingSamples = pendingSamples[s.qm.cfg.MaxSamplesPerSend:]
-			}
+
 				if !timer.Stop() {
-				<-timer.C
+					select {
+					case <-timer.C:
+					default:
+					}
 				}
 				timer.Reset(s.qm.cfg.BatchSendDeadline)
+			}
+
 		case <-timer.C:
 			if len(pendingSamples) > 0 {
 				s.sendSamples(pendingSamples)