Add field for last GC pause time (#2121)

CHANGELOG.md

@@ -27,6 +27,7 @@ in their config file.
 - [#2079](https://github.com/influxdata/telegraf/pull/2079): Enable setting ClientID in MQTT output.
 - [#2001](https://github.com/influxdata/telegraf/pull/2001): MongoDB input plugin: Improve state data.
 - [#2078](https://github.com/influxdata/telegraf/pull/2078): Ping input: add standard deviation field.
+- [#2121](https://github.com/influxdata/telegraf/pull/2121): Add GC pause metric to InfluxDB input plugin.
 
 ### Bugfixes
 

plugins/inputs/influxdb/influxdb.go

@@ -118,6 +118,7 @@ type memstats struct {
 	NextGC        int64      `json:"NextGC"`
 	LastGC        int64      `json:"LastGC"`
 	PauseTotalNs  int64      `json:"PauseTotalNs"`
+	PauseNs       [256]int64 `json:"PauseNs"`
 	NumGC         int64      `json:"NumGC"`
 	GCCPUFraction float64    `json:"GCCPUFraction"`
 }
@@ -202,6 +203,7 @@ func (i *InfluxDB) gatherURL(
 						"next_gc":         m.NextGC,
 						"last_gc":         m.LastGC,
 						"pause_total_ns":  m.PauseTotalNs,
+						"pause_ns":        m.PauseNs[(m.NumGC+255)%256],
 						"num_gc":          m.NumGC,
 						"gcc_pu_fraction": m.GCCPUFraction,
 					},

plugins/inputs/influxdb/influxdb_test.go

@@ -86,6 +86,7 @@ func TestInfluxDB(t *testing.T) {
 		"frees":           int64(381008),
 		"heap_idle":       int64(15802368),
 		"pause_total_ns":  int64(5132914),
+		"pause_ns":        int64(127053),
 		"lookups":         int64(77),
 		"heap_sys":        int64(33849344),
 		"mcache_sys":      int64(16384),