125 lines
3.0 KiB
Go
125 lines
3.0 KiB
Go
/*
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Copyright 2018 The Kubernetes Authors All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package metric
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import (
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"fmt"
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"math"
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"strconv"
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"strings"
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"sync"
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)
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const (
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initialNumBufSize = 24
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)
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var (
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numBufPool = sync.Pool{
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New: func() interface{} {
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b := make([]byte, 0, initialNumBufSize)
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return &b
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},
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}
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)
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// Type represents the type of a metric e.g. a counter. See
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// https://prometheus.io/docs/concepts/metric_types/.
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type Type string
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// Gauge defines a Prometheus gauge.
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var Gauge Type = "gauge"
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// Counter defines a Prometheus counter.
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var Counter Type = "counter"
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// Metric represents a single time series.
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type Metric struct {
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// The name of a metric is injected by its family to reduce duplication.
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LabelKeys []string
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LabelValues []string
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Value float64
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}
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func (m *Metric) Write(s *strings.Builder) {
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if len(m.LabelKeys) != len(m.LabelValues) {
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panic(fmt.Sprintf(
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"expected labelKeys %q to be of same length as labelValues %q",
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m.LabelKeys, m.LabelValues,
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))
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}
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labelsToString(s, m.LabelKeys, m.LabelValues)
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s.WriteByte(' ')
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writeFloat(s, m.Value)
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s.WriteByte('\n')
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}
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func labelsToString(m *strings.Builder, keys, values []string) {
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if len(keys) > 0 {
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var separator byte = '{'
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for i := 0; i < len(keys); i++ {
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m.WriteByte(separator)
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m.WriteString(keys[i])
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m.WriteString("=\"")
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escapeString(m, values[i])
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m.WriteByte('"')
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separator = ','
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}
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m.WriteByte('}')
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}
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}
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var (
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escapeWithDoubleQuote = strings.NewReplacer("\\", `\\`, "\n", `\n`, "\"", `\"`)
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)
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// escapeString replaces '\' by '\\', new line character by '\n', and '"' by
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// '\"'.
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// Taken from github.com/prometheus/common/expfmt/text_create.go.
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func escapeString(m *strings.Builder, v string) {
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escapeWithDoubleQuote.WriteString(m, v)
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}
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// writeFloat is equivalent to fmt.Fprint with a float64 argument but hardcodes
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// a few common cases for increased efficiency. For non-hardcoded cases, it uses
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// strconv.AppendFloat to avoid allocations, similar to writeInt.
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// Taken from github.com/prometheus/common/expfmt/text_create.go.
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func writeFloat(w *strings.Builder, f float64) {
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switch {
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case f == 1:
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w.WriteByte('1')
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case f == 0:
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w.WriteByte('0')
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case f == -1:
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w.WriteString("-1")
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case math.IsNaN(f):
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w.WriteString("NaN")
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case math.IsInf(f, +1):
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w.WriteString("+Inf")
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case math.IsInf(f, -1):
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w.WriteString("-Inf")
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default:
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bp := numBufPool.Get().(*[]byte)
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*bp = strconv.AppendFloat((*bp)[:0], f, 'g', -1, 64)
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w.Write(*bp)
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numBufPool.Put(bp)
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}
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}
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