Add memstats to the influxdb input plugin

closes #958

CHANGELOG.md

@@ -17,6 +17,7 @@ because the `value` field is redundant in the graphite/librato context.
 - [#939](https://github.com/influxdata/telegraf/pull/939): sysstat input plugin. Thanks @zbindenren!
 - [#998](https://github.com/influxdata/telegraf/pull/998): **breaking change** enabled global, user and ip queries in dovecot plugin. Thanks @mikif70!
 - [#1001](https://github.com/influxdata/telegraf/pull/1001): Graphite serializer templates.
+- [#1008](https://github.com/influxdata/telegraf/pull/1008): Adding memstats metrics to the influxdb plugin.
 
 ### Bugfixes
 - [#968](https://github.com/influxdata/telegraf/issues/968): Processes plugin gets unknown state when spaces are in (command name)

plugins/inputs/influxdb/README.md

@@ -1,6 +1,41 @@
 # influxdb plugin
 
-The influxdb plugin collects InfluxDB-formatted data from JSON endpoints.
+The InfluxDB plugin will collect metrics on the given InfluxDB servers.
+
+This plugin can also gather metrics from endpoints that expose
+InfluxDB-formatted endpoints. See below for more information.
+
+### Configuration:
+
+```toml
+# Read InfluxDB-formatted JSON metrics from one or more HTTP endpoints
+[[inputs.influxdb]]
+  ## Works with InfluxDB debug endpoints out of the box,
+  ## but other services can use this format too.
+  ## See the influxdb plugin's README for more details.
+
+  ## Multiple URLs from which to read InfluxDB-formatted JSON
+  urls = [
+    "http://localhost:8086/debug/vars"
+  ]
+```
+
+### Measurements & Fields
+
+- influxdb_database
+- influxdb_httpd
+- influxdb_measurement
+- influxdb_memstats
+- influxdb_shard
+- influxdb_subscriber
+- influxdb_tsm1_cache
+- influxdb_tsm1_wal
+- influxdb_write
+
+### InfluxDB-formatted endpoints
+
+The influxdb plugin can collect InfluxDB-formatted data from JSON endpoints.
+Whether associated with an Influx database or not.
 
 With a configuration of:
 
@@ -65,8 +100,11 @@ influxdb_transactions,url='http://192.168.2.1:8086/debug/vars' total=100.0,balan
 
 There are two important details to note about the collected metrics:
 
-1. Even though the values in JSON are being displayed as integers, the metrics are reported as floats.
+1. Even though the values in JSON are being displayed as integers,
+the metrics are reported as floats.
 JSON encoders usually don't print the fractional part for round floats.
-Because you cannot change the type of an existing field in InfluxDB, we assume all numbers are floats.
+Because you cannot change the type of an existing field in InfluxDB,
+we assume all numbers are floats.
 
-2. The top-level keys' names (in the example above, `"k1"`, `"k2"`, and `"k3"`) are not considered when recording the metrics.
+2. The top-level keys' names (in the example above, `"k1"`, `"k2"`, and `"k3"`)
+are not considered when recording the metrics.

plugins/inputs/influxdb/influxdb.go

@@ -71,6 +71,35 @@ type point struct {
 	Values map[string]interface{} `json:"values"`
 }
 
+type memstats struct {
+	Alloc         int64   `json:"Alloc"`
+	TotalAlloc    int64   `json:"TotalAlloc"`
+	Sys           int64   `json:"Sys"`
+	Lookups       int64   `json:"Lookups"`
+	Mallocs       int64   `json:"Mallocs"`
+	Frees         int64   `json:"Frees"`
+	HeapAlloc     int64   `json:"HeapAlloc"`
+	HeapSys       int64   `json:"HeapSys"`
+	HeapIdle      int64   `json:"HeapIdle"`
+	HeapInuse     int64   `json:"HeapInuse"`
+	HeapReleased  int64   `json:"HeapReleased"`
+	HeapObjects   int64   `json:"HeapObjects"`
+	StackInuse    int64   `json:"StackInuse"`
+	StackSys      int64   `json:"StackSys"`
+	MSpanInuse    int64   `json:"MSpanInuse"`
+	MSpanSys      int64   `json:"MSpanSys"`
+	MCacheInuse   int64   `json:"MCacheInuse"`
+	MCacheSys     int64   `json:"MCacheSys"`
+	BuckHashSys   int64   `json:"BuckHashSys"`
+	GCSys         int64   `json:"GCSys"`
+	OtherSys      int64   `json:"OtherSys"`
+	NextGC        int64   `json:"NextGC"`
+	LastGC        int64   `json:"LastGC"`
+	PauseTotalNs  int64   `json:"PauseTotalNs"`
+	NumGC         int64   `json:"NumGC"`
+	GCCPUFraction float64 `json:"GCCPUFraction"`
+}
+
 var tr = &http.Transport{
 	ResponseHeaderTimeout: time.Duration(3 * time.Second),
 }
@@ -118,12 +147,52 @@ func (i *InfluxDB) gatherURL(
 			break
 		}
 
-		// Read in a string key. We don't do anything with the top-level keys, so it's discarded.
-		_, err := dec.Token()
+		// Read in a string key. We don't do anything with the top-level keys,
+		// so it's discarded.
+		key, err := dec.Token()
 		if err != nil {
 			return err
 		}
 
+		if key.(string) == "memstats" {
+			var m memstats
+			if err := dec.Decode(&m); err != nil {
+				continue
+			}
+			acc.AddFields("influxdb_memstats",
+				map[string]interface{}{
+					"alloc":           m.Alloc,
+					"total_alloc":     m.TotalAlloc,
+					"sys":             m.Sys,
+					"lookups":         m.Lookups,
+					"mallocs":         m.Mallocs,
+					"frees":           m.Frees,
+					"heap_alloc":      m.HeapAlloc,
+					"heap_sys":        m.HeapSys,
+					"heap_idle":       m.HeapIdle,
+					"heap_inuse":      m.HeapInuse,
+					"heap_released":   m.HeapReleased,
+					"heap_objects":    m.HeapObjects,
+					"stack_inuse":     m.StackInuse,
+					"stack_sys":       m.StackSys,
+					"mspan_inuse":     m.MSpanInuse,
+					"mspan_sys":       m.MSpanSys,
+					"mcache_inuse":    m.MCacheInuse,
+					"mcache_sys":      m.MCacheSys,
+					"buck_hash_sys":   m.BuckHashSys,
+					"gc_sys":          m.GCSys,
+					"other_sys":       m.OtherSys,
+					"next_gc":         m.NextGC,
+					"last_gc":         m.LastGC,
+					"pause_total_ns":  m.PauseTotalNs,
+					"num_gc":          m.NumGC,
+					"gcc_pu_fraction": m.GCCPUFraction,
+				},
+				map[string]string{
+					"url": url,
+				})
+		}
+
 		// Attempt to parse a whole object into a point.
 		// It might be a non-object, like a string or array.
 		// If we fail to decode it into a point, ignore it and move on.
@@ -132,7 +201,8 @@ func (i *InfluxDB) gatherURL(
 			continue
 		}
 
-		// If the object was a point, but was not fully initialized, ignore it and move on.
+		// If the object was a point, but was not fully initialized,
+		// ignore it and move on.
 		if p.Name == "" || p.Tags == nil || p.Values == nil || len(p.Values) == 0 {
 			continue
 		}