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labels.go
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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 (
"bufio"
"bytes"
"os"
"sort"
"strconv"
"strings"
"github.com/cespare/xxhash"
"github.com/pkg/errors"
)
const sep = '\xff'
// 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(',')
}
b.WriteString(l.Name)
b.WriteByte('=')
b.WriteString(strconv.Quote(l.Value))
}
b.WriteByte('}')
return b.String()
}
// 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)
}
// 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 ""
}
// Equals returns whether the two label sets are equal.
func (ls Labels) Equals(o Labels) bool {
if len(ls) != len(o) {
return false
}
for i, l := range ls {
if o[i] != l {
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)
}
// Slice is a sortable slice of label sets.
type Slice []Labels
func (s Slice) Len() int { return len(s) }
func (s Slice) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
func (s Slice) Less(i, j int) bool { return Compare(s[i], s[j]) < 0 }
// ReadLabels reads up to n label sets in a JSON formatted file fn. It is mostly useful
// to load testing data.
func ReadLabels(fn string, n int) ([]Labels, error) {
f, err := os.Open(fn)
if err != nil {
return nil, err
}
defer f.Close()
scanner := bufio.NewScanner(f)
var mets []Labels
hashes := map[uint64]struct{}{}
i := 0
for scanner.Scan() && i < n {
m := make(Labels, 0, 10)
r := strings.NewReplacer("\"", "", "{", "", "}", "")
s := r.Replace(scanner.Text())
labelChunks := strings.Split(s, ",")
for _, labelChunk := range labelChunks {
split := strings.Split(labelChunk, ":")
m = append(m, Label{Name: split[0], Value: split[1]})
}
// Order of the k/v labels matters, don't assume we'll always receive them already sorted.
sort.Sort(m)
h := m.Hash()
if _, ok := hashes[h]; ok {
continue
}
mets = append(mets, m)
hashes[h] = struct{}{}
i++
}
if err != nil {
return nil, err
}
if i != n {
return mets, errors.Errorf("requested %d metrics but found %d", n, i)
}
return mets, nil
}