Use mutex to ensure only on flush timer is running

sinks/influxSink.go

@@ -41,10 +41,11 @@ type InfluxSink struct {
 		// Default: 100
 		DropRate int `json:"drop_rate,omitempty"`
 	}
-	batch      []*write.Point
-	flushTimer *time.Timer
-	flushDelay time.Duration
-	batchMutex sync.Mutex // Flush() runs in another goroutine, so this lock has to protect the buffer
+	batch           []*write.Point
+	flushTimer      *time.Timer
+	flushDelay      time.Duration
+	batchMutex      sync.Mutex // Flush() runs in another goroutine, so this lock has to protect the buffer
+	flushTimerMutex sync.Mutex // Ensure only one flush timer is running
 }
 
 // connect connects to the InfluxDB server
@@ -103,16 +104,17 @@ func (s *InfluxSink) connect() error {
 
 func (s *InfluxSink) Write(m lp.CCMetric) error {
 
-	if s.flushDelay != 0 && s.flushTimer == nil {
+	if s.flushDelay != 0 && s.flushTimerMutex.TryLock() {
 		// Run a batched flush for all metrics that arrived in the last flush delay interval
+		cclog.ComponentDebug(s.name, "Starting new flush timer")
 		s.flushTimer = time.AfterFunc(
 			s.flushDelay,
 			func() {
-				err := s.Flush()
-				if err != nil {
+				defer s.flushTimerMutex.Unlock()
+				cclog.ComponentDebug(s.name, "Starting flush in flush timer")
+				if err := s.Flush(); err != nil {
 					cclog.ComponentError(s.name, "Flush timer: flush failed:", err)
 				}
-				s.flushTimer = nil
 			})
 	}
 
@@ -131,7 +133,7 @@ func (s *InfluxSink) Write(m lp.CCMetric) error {
 			s.batch[i] = nil
 		}
 		s.batch = s.batch[:newSize]
-		cclog.ComponentError(s.name, "Batch slice full, dropping ", s.config.DropRate, "oldest metric(s)")
+		cclog.ComponentError(s.name, "Batch slice full, dropping", s.config.DropRate, "oldest metric(s)")
 	}
 
 	// Append metric to batch slice