prometheus/pkg/labels/labels.go

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// Copyright 2017 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 labels
import (
"bytes"
"encoding/json"
"sort"
"strconv"
"strings"
"github.com/cespare/xxhash"
)
const sep = '\xff'
// Well-known label names used by Prometheus components.
const (
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MetricName = "__name__"
AlertName = "alertname"
BucketLabel = "le"
InstanceName = "instance"
)
// Label is a key/value pair of strings.
type Label struct {
Name, Value string
}
// Labels is a sorted set of labels. Order has to be guaranteed upon
// instantiation.
type Labels []Label
func (ls Labels) Len() int { return len(ls) }
func (ls Labels) Swap(i, j int) { ls[i], ls[j] = ls[j], ls[i] }
func (ls Labels) Less(i, j int) bool { return ls[i].Name < ls[j].Name }
func (ls Labels) String() string {
var b bytes.Buffer
b.WriteByte('{')
for i, l := range ls {
if i > 0 {
b.WriteByte(',')
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b.WriteByte(' ')
}
b.WriteString(l.Name)
b.WriteByte('=')
b.WriteString(strconv.Quote(l.Value))
}
b.WriteByte('}')
return b.String()
}
// MarshalJSON implements json.Marshaler.
func (ls Labels) MarshalJSON() ([]byte, error) {
return json.Marshal(ls.Map())
}
// UnmarshalJSON implements json.Unmarshaler.
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func (ls *Labels) UnmarshalJSON(b []byte) error {
var m map[string]string
if err := json.Unmarshal(b, &m); err != nil {
return err
}
*ls = FromMap(m)
return nil
}
// Hash returns a hash value for the label set.
func (ls Labels) Hash() uint64 {
b := make([]byte, 0, 1024)
for _, v := range ls {
b = append(b, v.Name...)
b = append(b, sep)
b = append(b, v.Value...)
b = append(b, sep)
}
return xxhash.Sum64(b)
}
// Copy returns a copy of the labels.
func (ls Labels) Copy() Labels {
res := make(Labels, len(ls))
copy(res, ls)
return res
}
// Get returns the value for the label with the given name.
// Returns an empty string if the label doesn't exist.
func (ls Labels) Get(name string) string {
for _, l := range ls {
if l.Name == name {
return l.Value
}
}
return ""
}
// Equal returns whether the two label sets are equal.
func Equal(ls, o Labels) bool {
if len(ls) != len(o) {
return false
}
for i, l := range ls {
if l.Name != o[i].Name || l.Value != o[i].Value {
return false
}
}
return true
}
// Map returns a string map of the labels.
func (ls Labels) Map() map[string]string {
m := make(map[string]string, len(ls))
for _, l := range ls {
m[l.Name] = l.Value
}
return m
}
// New returns a sorted Labels from the given labels.
// The caller has to guarantee that all label names are unique.
func New(ls ...Label) Labels {
set := make(Labels, 0, len(ls))
for _, l := range ls {
set = append(set, l)
}
sort.Sort(set)
return set
}
// FromMap returns new sorted Labels from the given map.
func FromMap(m map[string]string) Labels {
l := make([]Label, 0, len(m))
for k, v := range m {
l = append(l, Label{Name: k, Value: v})
}
return New(l...)
}
// FromStrings creates new labels from pairs of strings.
func FromStrings(ss ...string) Labels {
if len(ss)%2 != 0 {
panic("invalid number of strings")
}
var res Labels
for i := 0; i < len(ss); i += 2 {
res = append(res, Label{Name: ss[i], Value: ss[i+1]})
}
sort.Sort(res)
return res
}
// Compare compares the two label sets.
// The result will be 0 if a==b, <0 if a < b, and >0 if a > b.
func Compare(a, b Labels) int {
l := len(a)
if len(b) < l {
l = len(b)
}
for i := 0; i < l; i++ {
if d := strings.Compare(a[i].Name, b[i].Name); d != 0 {
return d
}
if d := strings.Compare(a[i].Value, b[i].Value); d != 0 {
return d
}
}
// If all labels so far were in common, the set with fewer labels comes first.
return len(a) - len(b)
}
// Builder allows modifiying Labels.
type Builder struct {
base Labels
del []string
add []Label
}
// NewBuilder returns a new LabelsBuilder
func NewBuilder(base Labels) *Builder {
return &Builder{
base: base,
del: make([]string, 0, 5),
add: make([]Label, 0, 5),
}
}
// Del deletes the label of the given name.
func (b *Builder) Del(ns ...string) *Builder {
for _, n := range ns {
for i, a := range b.add {
if a.Name == n {
b.add = append(b.add[:i], b.add[i+1:]...)
}
}
b.del = append(b.del, n)
}
return b
}
// Set the name/value pair as a label.
func (b *Builder) Set(n, v string) *Builder {
for i, a := range b.add {
if a.Name == n {
b.add[i].Value = v
return b
}
}
b.add = append(b.add, Label{Name: n, Value: v})
return b
}
// Labels returns the labels from the builder. If no modifications
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// were made, the original labels are returned.
func (b *Builder) Labels() Labels {
if len(b.del) == 0 && len(b.add) == 0 {
return b.base
}
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// In the general case, labels are removed, modified or moved
// rather than added.
res := make(Labels, 0, len(b.base))
Outer:
for _, l := range b.base {
for _, n := range b.del {
if l.Name == n {
continue Outer
}
}
for _, la := range b.add {
if l.Name == la.Name {
continue Outer
}
}
res = append(res, l)
}
res = append(res, b.add...)
sort.Sort(res)
return res
}