Reconnect before sending graphite metrics if disconnected (#3680)

(cherry picked from commit f374a29)

Author: piotr1212

plugins/outputs/graphite/graphite.go

@@ -155,8 +155,22 @@ func (g *Graphite) Write(metrics []telegraf.Metric) error {
 		batch = append(batch, buf...)
 	}
 
+	err = g.send(batch)
+
+	// try to reconnect and retry to send
+	if err != nil {
+		log.Println("E! Graphite: Reconnecting and retrying: ")
+		g.Connect()
+		err = g.send(batch)
+	}
+
+	return err
+}
+
+func (g *Graphite) send(batch []byte) error {
 	// This will get set to nil if a successful write occurs
-	err = errors.New("Could not write to any Graphite server in cluster\n")
+	err := errors.New("Could not write to any Graphite server in cluster\n")
+
 	// Send data to a random server
 	p := rand.Perm(len(g.conns))
 	for _, n := range p {
@@ -167,18 +181,16 @@ func (g *Graphite) Write(metrics []telegraf.Metric) error {
 		if _, e := g.conns[n].Write(batch); e != nil {
 			// Error
 			log.Println("E! Graphite Error: " + e.Error())
+			// Close explicitely
+			g.conns[n].Close()
 			// Let's try the next one
 		} else {
 			// Success
 			err = nil
 			break
 		}
 	}
-	// try to reconnect
-	if err != nil {
-		log.Println("E! Reconnecting: ")
-		g.Connect()
-	}
+
 	return err
 }
 

plugins/outputs/graphite/graphite_test.go

@@ -81,18 +81,16 @@ func TestGraphiteOK(t *testing.T) {
 	err2 := g.Write(metrics)
 	require.NoError(t, err2)
 
-	// Waiting TCPserver
+	// Waiting TCPserver, should reconnect and resend
 	wg.Wait()
 	t.Log("Finished Waiting for first data")
 	var wg2 sync.WaitGroup
 	// Start TCP server
 	wg2.Add(1)
 	TCPServer2(t, &wg2)
 	//Write but expect an error, but reconnect
-	g.Write(metrics2)
 	err3 := g.Write(metrics2)
-	t.Log("Finished writing second data, it should have failed")
-	//Actually write the new metrics
+	t.Log("Finished writing second data, it should have reconnected automatically")
 
 	require.NoError(t, err3)
 	t.Log("Finished writing third data")