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/timer_test.go

@@ -0,0 +1,101 @@
+package metrics
+
+import (
+	"fmt"
+	"math"
+	"testing"
+	"time"
+)
+
+func BenchmarkTimer(b *testing.B) {
+	tm := NewTimer()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		tm.Update(1)
+	}
+}
+
+func TestGetOrRegisterTimer(t *testing.T) {
+	r := NewRegistry()
+	NewRegisteredTimer("foo", r).Update(47)
+	if tm := GetOrRegisterTimer("foo", r); 1 != tm.Count() {
+		t.Fatal(tm)
+	}
+}
+
+func TestTimerExtremes(t *testing.T) {
+	tm := NewTimer()
+	tm.Update(math.MaxInt64)
+	tm.Update(0)
+	if stdDev := tm.StdDev(); 4.611686018427388e+18 != stdDev {
+		t.Errorf("tm.StdDev(): 4.611686018427388e+18 != %v\n", stdDev)
+	}
+}
+
+func TestTimerStop(t *testing.T) {
+	l := len(arbiter.meters)
+	tm := NewTimer()
+	if len(arbiter.meters) != l+1 {
+		t.Errorf("arbiter.meters: %d != %d\n", l+1, len(arbiter.meters))
+	}
+	tm.Stop()
+	if len(arbiter.meters) != l {
+		t.Errorf("arbiter.meters: %d != %d\n", l, len(arbiter.meters))
+	}
+}
+
+func TestTimerFunc(t *testing.T) {
+	tm := NewTimer()
+	tm.Time(func() { time.Sleep(50e6) })
+	if max := tm.Max(); 45e6 > max || max > 55e6 {
+		t.Errorf("tm.Max(): 45e6 > %v || %v > 55e6\n", max, max)
+	}
+}
+
+func TestTimerZero(t *testing.T) {
+	tm := NewTimer()
+	if count := tm.Count(); 0 != count {
+		t.Errorf("tm.Count(): 0 != %v\n", count)
+	}
+	if min := tm.Min(); 0 != min {
+		t.Errorf("tm.Min(): 0 != %v\n", min)
+	}
+	if max := tm.Max(); 0 != max {
+		t.Errorf("tm.Max(): 0 != %v\n", max)
+	}
+	if mean := tm.Mean(); 0.0 != mean {
+		t.Errorf("tm.Mean(): 0.0 != %v\n", mean)
+	}
+	if stdDev := tm.StdDev(); 0.0 != stdDev {
+		t.Errorf("tm.StdDev(): 0.0 != %v\n", stdDev)
+	}
+	ps := tm.Percentiles([]float64{0.5, 0.75, 0.99})
+	if 0.0 != ps[0] {
+		t.Errorf("median: 0.0 != %v\n", ps[0])
+	}
+	if 0.0 != ps[1] {
+		t.Errorf("75th percentile: 0.0 != %v\n", ps[1])
+	}
+	if 0.0 != ps[2] {
+		t.Errorf("99th percentile: 0.0 != %v\n", ps[2])
+	}
+	if rate1 := tm.Rate1(); 0.0 != rate1 {
+		t.Errorf("tm.Rate1(): 0.0 != %v\n", rate1)
+	}
+	if rate5 := tm.Rate5(); 0.0 != rate5 {
+		t.Errorf("tm.Rate5(): 0.0 != %v\n", rate5)
+	}
+	if rate15 := tm.Rate15(); 0.0 != rate15 {
+		t.Errorf("tm.Rate15(): 0.0 != %v\n", rate15)
+	}
+	if rateMean := tm.RateMean(); 0.0 != rateMean {
+		t.Errorf("tm.RateMean(): 0.0 != %v\n", rateMean)
+	}
+}
+
+func ExampleGetOrRegisterTimer() {
+	m := "account.create.latency"
+	t := GetOrRegisterTimer(m, nil)
+	t.Update(47)
+	fmt.Println(t.Max()) // Output: 47
+}