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/syslog.go

@@ -0,0 +1,78 @@
+// +build !windows
+
+package metrics
+
+import (
+	"fmt"
+	"log/syslog"
+	"time"
+)
+
+// Output each metric in the given registry to syslog periodically using
+// the given syslogger.
+func Syslog(r Registry, d time.Duration, w *syslog.Writer) {
+	for range time.Tick(d) {
+		r.Each(func(name string, i interface{}) {
+			switch metric := i.(type) {
+			case Counter:
+				w.Info(fmt.Sprintf("counter %s: count: %d", name, metric.Count()))
+			case Gauge:
+				w.Info(fmt.Sprintf("gauge %s: value: %d", name, metric.Value()))
+			case GaugeFloat64:
+				w.Info(fmt.Sprintf("gauge %s: value: %f", name, metric.Value()))
+			case Healthcheck:
+				metric.Check()
+				w.Info(fmt.Sprintf("healthcheck %s: error: %v", name, metric.Error()))
+			case Histogram:
+				h := metric.Snapshot()
+				ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+				w.Info(fmt.Sprintf(
+					"histogram %s: count: %d min: %d max: %d mean: %.2f stddev: %.2f median: %.2f 75%%: %.2f 95%%: %.2f 99%%: %.2f 99.9%%: %.2f",
+					name,
+					h.Count(),
+					h.Min(),
+					h.Max(),
+					h.Mean(),
+					h.StdDev(),
+					ps[0],
+					ps[1],
+					ps[2],
+					ps[3],
+					ps[4],
+				))
+			case Meter:
+				m := metric.Snapshot()
+				w.Info(fmt.Sprintf(
+					"meter %s: count: %d 1-min: %.2f 5-min: %.2f 15-min: %.2f mean: %.2f",
+					name,
+					m.Count(),
+					m.Rate1(),
+					m.Rate5(),
+					m.Rate15(),
+					m.RateMean(),
+				))
+			case Timer:
+				t := metric.Snapshot()
+				ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+				w.Info(fmt.Sprintf(
+					"timer %s: count: %d min: %d max: %d mean: %.2f stddev: %.2f median: %.2f 75%%: %.2f 95%%: %.2f 99%%: %.2f 99.9%%: %.2f 1-min: %.2f 5-min: %.2f 15-min: %.2f mean-rate: %.2f",
+					name,
+					t.Count(),
+					t.Min(),
+					t.Max(),
+					t.Mean(),
+					t.StdDev(),
+					ps[0],
+					ps[1],
+					ps[2],
+					ps[3],
+					ps[4],
+					t.Rate1(),
+					t.Rate5(),
+					t.Rate15(),
+					t.RateMean(),
+				))
+			}
+		})
+	}
+}