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

vendor/github.com/influxdata/influxdb/pkg/escape/bytes.go

@@ -0,0 +1,115 @@
+// Package escape contains utilities for escaping parts of InfluxQL
+// and InfluxDB line protocol.
+package escape // import "github.com/influxdata/influxdb/pkg/escape"
+
+import (
+	"bytes"
+	"strings"
+)
+
+// Codes is a map of bytes to be escaped.
+var Codes = map[byte][]byte{
+	',': []byte(`\,`),
+	'"': []byte(`\"`),
+	' ': []byte(`\ `),
+	'=': []byte(`\=`),
+}
+
+// Bytes escapes characters on the input slice, as defined by Codes.
+func Bytes(in []byte) []byte {
+	for b, esc := range Codes {
+		in = bytes.Replace(in, []byte{b}, esc, -1)
+	}
+	return in
+}
+
+const escapeChars = `," =`
+
+// IsEscaped returns whether b has any escaped characters,
+// i.e. whether b seems to have been processed by Bytes.
+func IsEscaped(b []byte) bool {
+	for len(b) > 0 {
+		i := bytes.IndexByte(b, '\\')
+		if i < 0 {
+			return false
+		}
+
+		if i+1 < len(b) && strings.IndexByte(escapeChars, b[i+1]) >= 0 {
+			return true
+		}
+		b = b[i+1:]
+	}
+	return false
+}
+
+// AppendUnescaped appends the unescaped version of src to dst
+// and returns the resulting slice.
+func AppendUnescaped(dst, src []byte) []byte {
+	var pos int
+	for len(src) > 0 {
+		next := bytes.IndexByte(src[pos:], '\\')
+		if next < 0 || pos+next+1 >= len(src) {
+			return append(dst, src...)
+		}
+
+		if pos+next+1 < len(src) && strings.IndexByte(escapeChars, src[pos+next+1]) >= 0 {
+			if pos+next > 0 {
+				dst = append(dst, src[:pos+next]...)
+			}
+			src = src[pos+next+1:]
+			pos = 0
+		} else {
+			pos += next + 1
+		}
+	}
+
+	return dst
+}
+
+// Unescape returns a new slice containing the unescaped version of in.
+func Unescape(in []byte) []byte {
+	if len(in) == 0 {
+		return nil
+	}
+
+	if bytes.IndexByte(in, '\\') == -1 {
+		return in
+	}
+
+	i := 0
+	inLen := len(in)
+
+	// The output size will be no more than inLen. Preallocating the
+	// capacity of the output is faster and uses less memory than
+	// letting append() do its own (over)allocation.
+	out := make([]byte, 0, inLen)
+
+	for {
+		if i >= inLen {
+			break
+		}
+		if in[i] == '\\' && i+1 < inLen {
+			switch in[i+1] {
+			case ',':
+				out = append(out, ',')
+				i += 2
+				continue
+			case '"':
+				out = append(out, '"')
+				i += 2
+				continue
+			case ' ':
+				out = append(out, ' ')
+				i += 2
+				continue
+			case '=':
+				out = append(out, '=')
+				i += 2
+				continue
+			}
+		}
+		out = append(out, in[i])
+		i += 1
+	}
+	return out
+}

vendor/github.com/influxdata/influxdb/pkg/escape/strings.go

@@ -0,0 +1,21 @@
+package escape
+
+import "strings"
+
+var (
+	escaper   = strings.NewReplacer(`,`, `\,`, `"`, `\"`, ` `, `\ `, `=`, `\=`)
+	unescaper = strings.NewReplacer(`\,`, `,`, `\"`, `"`, `\ `, ` `, `\=`, `=`)
+)
+
+// UnescapeString returns unescaped version of in.
+func UnescapeString(in string) string {
+	if strings.IndexByte(in, '\\') == -1 {
+		return in
+	}
+	return unescaper.Replace(in)
+}
+
+// String returns the escaped version of in.
+func String(in string) string {
+	return escaper.Replace(in)
+}