metrics: pull library and introduce ResettingTimer and InfluxDB reporter (#15910)

* go-metrics: fork library and introduce ResettingTimer and InfluxDB reporter.

* vendor: change nonsense/go-metrics to ethersphere/go-metrics

* go-metrics: add tests. move ResettingTimer logic from reporter to type.

* all, metrics: pull in metrics package in go-ethereum

* metrics/test: make sure metrics are enabled for tests

* metrics: apply gosimple rules

* metrics/exp, internal/debug: init expvar endpoint when starting pprof server

* internal/debug: tiny comment formatting fix

metrics/metrics_test.go

@@ -0,0 +1,124 @@
+package metrics
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"sync"
+	"testing"
+)
+
+const FANOUT = 128
+
+// Stop the compiler from complaining during debugging.
+var (
+	_ = ioutil.Discard
+	_ = log.LstdFlags
+)
+
+func BenchmarkMetrics(b *testing.B) {
+	r := NewRegistry()
+	c := NewRegisteredCounter("counter", r)
+	g := NewRegisteredGauge("gauge", r)
+	gf := NewRegisteredGaugeFloat64("gaugefloat64", r)
+	h := NewRegisteredHistogram("histogram", r, NewUniformSample(100))
+	m := NewRegisteredMeter("meter", r)
+	t := NewRegisteredTimer("timer", r)
+	RegisterDebugGCStats(r)
+	RegisterRuntimeMemStats(r)
+	b.ResetTimer()
+	ch := make(chan bool)
+
+	wgD := &sync.WaitGroup{}
+	/*
+		wgD.Add(1)
+		go func() {
+			defer wgD.Done()
+			//log.Println("go CaptureDebugGCStats")
+			for {
+				select {
+				case <-ch:
+					//log.Println("done CaptureDebugGCStats")
+					return
+				default:
+					CaptureDebugGCStatsOnce(r)
+				}
+			}
+		}()
+	//*/
+
+	wgR := &sync.WaitGroup{}
+	//*
+	wgR.Add(1)
+	go func() {
+		defer wgR.Done()
+		//log.Println("go CaptureRuntimeMemStats")
+		for {
+			select {
+			case <-ch:
+				//log.Println("done CaptureRuntimeMemStats")
+				return
+			default:
+				CaptureRuntimeMemStatsOnce(r)
+			}
+		}
+	}()
+	//*/
+
+	wgW := &sync.WaitGroup{}
+	/*
+		wgW.Add(1)
+		go func() {
+			defer wgW.Done()
+			//log.Println("go Write")
+			for {
+				select {
+				case <-ch:
+					//log.Println("done Write")
+					return
+				default:
+					WriteOnce(r, ioutil.Discard)
+				}
+			}
+		}()
+	//*/
+
+	wg := &sync.WaitGroup{}
+	wg.Add(FANOUT)
+	for i := 0; i < FANOUT; i++ {
+		go func(i int) {
+			defer wg.Done()
+			//log.Println("go", i)
+			for i := 0; i < b.N; i++ {
+				c.Inc(1)
+				g.Update(int64(i))
+				gf.Update(float64(i))
+				h.Update(int64(i))
+				m.Mark(1)
+				t.Update(1)
+			}
+			//log.Println("done", i)
+		}(i)
+	}
+	wg.Wait()
+	close(ch)
+	wgD.Wait()
+	wgR.Wait()
+	wgW.Wait()
+}
+
+func Example() {
+	c := NewCounter()
+	Register("money", c)
+	c.Inc(17)
+
+	// Threadsafe registration
+	t := GetOrRegisterTimer("db.get.latency", nil)
+	t.Time(func() {})
+	t.Update(1)
+
+	fmt.Println(c.Count())
+	fmt.Println(t.Min())
+	// Output: 17
+	// 1
+}