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metric.go
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metric.go
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// Copyright 2013 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package model
import (
"encoding/json"
"fmt"
"sort"
"strings"
)
var separator = []byte{0}
// A Metric is similar to a LabelSet, but the key difference is that a Metric is
// a singleton and refers to one and only one stream of samples.
type Metric map[LabelName]LabelValue
// Equal compares the metrics.
func (m Metric) Equal(o Metric) bool {
if len(m) != len(o) {
return false
}
for ln, lv := range m {
olv, ok := o[ln]
if !ok {
return false
}
if olv != lv {
return false
}
}
return true
}
// Before compares the metrics, using the following criteria:
//
// If m has fewer labels than o, it is before o. If it has more, it is not.
//
// If the number of labels is the same, the superset of all label names is
// sorted alphanumerically. The first differing label pair found in that order
// determines the outcome: If the label does not exist at all in m, then m is
// before o, and vice versa. Otherwise the label value is compared
// alphanumerically.
//
// If m and o are equal, the method returns false.
func (m Metric) Before(o Metric) bool {
if len(m) < len(o) {
return true
}
if len(m) > len(o) {
return false
}
lns := make(LabelNames, 0, len(m)+len(o))
for ln := range m {
lns = append(lns, ln)
}
for ln := range o {
lns = append(lns, ln)
}
// It's probably not worth it to de-dup lns.
sort.Sort(lns)
for _, ln := range lns {
mlv, ok := m[ln]
if !ok {
return true
}
olv, ok := o[ln]
if !ok {
return false
}
if mlv < olv {
return true
}
if mlv > olv {
return false
}
}
return false
}
// String implements Stringer.
func (m Metric) String() string {
metricName, hasName := m[MetricNameLabel]
numLabels := len(m) - 1
if !hasName {
numLabels = len(m)
}
labelStrings := make([]string, 0, numLabels)
for label, value := range m {
if label != MetricNameLabel {
labelStrings = append(labelStrings, fmt.Sprintf("%s=%q", label, value))
}
}
switch numLabels {
case 0:
if hasName {
return string(metricName)
}
return "{}"
default:
sort.Strings(labelStrings)
return fmt.Sprintf("%s{%s}", metricName, strings.Join(labelStrings, ", "))
}
}
// Fingerprint returns a Metric's Fingerprint.
func (m Metric) Fingerprint() Fingerprint {
return metricToFingerprint(m)
}
// FastFingerprint returns a Metric's Fingerprint calculated by a faster hashing
// algorithm, which is, however, more susceptible to hash collisions.
func (m Metric) FastFingerprint() Fingerprint {
return metricToFastFingerprint(m)
}
// Clone returns a copy of the Metric.
func (m Metric) Clone() Metric {
clone := Metric{}
for k, v := range m {
clone[k] = v
}
return clone
}
// MergeFromLabelSet merges a label set into this Metric, prefixing a collision
// prefix to the label names merged from the label set where required.
func (m Metric) MergeFromLabelSet(labels LabelSet, collisionPrefix LabelName) {
for k, v := range labels {
if collisionPrefix != "" {
for {
if _, exists := m[k]; !exists {
break
}
k = collisionPrefix + k
}
}
m[k] = v
}
}
// COWMetric wraps a Metric to enable copy-on-write access patterns.
type COWMetric struct {
Copied bool
Metric Metric
}
// Set sets a label name in the wrapped Metric to a given value and copies the
// Metric initially, if it is not already a copy.
func (m *COWMetric) Set(ln LabelName, lv LabelValue) {
m.doCOW()
m.Metric[ln] = lv
}
// Delete deletes a given label name from the wrapped Metric and copies the
// Metric initially, if it is not already a copy.
func (m *COWMetric) Delete(ln LabelName) {
m.doCOW()
delete(m.Metric, ln)
}
// doCOW copies the underlying Metric if it is not already a copy.
func (m *COWMetric) doCOW() {
if !m.Copied {
m.Metric = m.Metric.Clone()
m.Copied = true
}
}
// String implements fmt.Stringer.
func (m COWMetric) String() string {
return m.Metric.String()
}
// MarshalJSON implements json.Marshaler.
func (m COWMetric) MarshalJSON() ([]byte, error) {
return json.Marshal(m.Metric)
}