goCollector: add thread count gauge in goCollector

Signed-off-by: Peng Gao <peng.gao.dut@gmail.com>

prometheus/go_collector.go

@@ -9,6 +9,7 @@ import (
 
 type goCollector struct {
 	goroutines Gauge
+	threads    Gauge
 	gcDesc     *Desc
 
 	// metrics to describe and collect
@@ -24,6 +25,11 @@ func NewGoCollector() Collector {
 			Name:      "goroutines",
 			Help:      "Number of goroutines that currently exist.",
 		}),
+		threads: NewGauge(GaugeOpts{
+			Namespace: "go",
+			Name:      "threads",
+			Help:      "Number of threads created.",
+		}),
 		gcDesc: NewDesc(
 			"go_gc_duration_seconds",
 			"A summary of the GC invocation durations.",
@@ -225,8 +231,8 @@ func memstatNamespace(s string) string {
 // Describe returns all descriptions of the collector.
 func (c *goCollector) Describe(ch chan<- *Desc) {
 	ch <- c.goroutines.Desc()
+	ch <- c.threads.Desc()
 	ch <- c.gcDesc
-
 	for _, i := range c.metrics {
 		ch <- i.desc
 	}
@@ -236,6 +242,9 @@ func (c *goCollector) Describe(ch chan<- *Desc) {
 func (c *goCollector) Collect(ch chan<- Metric) {
 	c.goroutines.Set(float64(runtime.NumGoroutine()))
 	ch <- c.goroutines
+	n, _ := runtime.ThreadCreateProfile(nil)
+	c.threads.Set(float64(n))
+	ch <- c.threads
 
 	var stats debug.GCStats
 	stats.PauseQuantiles = make([]time.Duration, 5)

prometheus/go_collector_test.go

@@ -33,6 +33,9 @@ func TestGoCollector(t *testing.T) {
 			switch m := metric.(type) {
 			// Attention, this also catches Counter...
 			case Gauge:
+				if m.Desc().fqName != "go_goroutines" {
+					continue
+				}
 				pb := &dto.Metric{}
 				m.Write(pb)
 				if pb.GetGauge() == nil {
@@ -50,10 +53,11 @@ func TestGoCollector(t *testing.T) {
 					t.Errorf("want 1 new goroutine, got %d", diff)
 				}
 
-				// GoCollector performs two sends per call.
+				// GoCollector performs three sends per call.
 				// On line 27 we need to receive the second send
 				// to shut down cleanly.
 				<-ch
+				<-ch
 				return
 			}
 		case <-time.After(1 * time.Second):