Do not write metrics if there are 0 to write

closes #884

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 ### Bugfixes
 [#890](https://github.com/influxdata/telegraf/issues/890): Create TLS config even if only ssl_ca is provided.
+[#884](https://github.com/influxdata/telegraf/issues/884): Do not call write method if there are 0 metrics to write.
 
 ## v0.11.1 [2016-03-17]
 

internal/models/running_output.go

@@ -121,6 +121,9 @@ func (ro *RunningOutput) Write() error {
 }
 
 func (ro *RunningOutput) write(metrics []telegraf.Metric) error {
+	if len(metrics) == 0 {
+		return nil
+	}
 	start := time.Now()
 	err := ro.Output.Write(metrics)
 	elapsed := time.Since(start)