prometheus/model/labels/labels_common.go
Bryan Boreham 0bb5588386
labels: optimize String method (#13673)
Use a stack buffer to reduce memory allocations.

`Write(AppendQuote(AvailableBuffer` does not allocate or copy when
the buffer has sufficient space.

Also add a benchmark, with some refactoring.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
2024-03-12 11:34:03 +00:00

218 lines
4.8 KiB
Go

// 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"
"slices"
"strconv"
"github.com/prometheus/common/model"
)
const (
MetricName = "__name__"
AlertName = "alertname"
BucketLabel = "le"
InstanceName = "instance"
labelSep = '\xfe'
)
var seps = []byte{'\xff'}
// Label is a key/value pair of strings.
type Label struct {
Name, Value string
}
func (ls Labels) String() string {
var bytea [1024]byte // On stack to avoid memory allocation while building the output.
b := bytes.NewBuffer(bytea[:0])
b.WriteByte('{')
i := 0
ls.Range(func(l Label) {
if i > 0 {
b.WriteByte(',')
b.WriteByte(' ')
}
b.WriteString(l.Name)
b.WriteByte('=')
b.Write(strconv.AppendQuote(b.AvailableBuffer(), l.Value))
i++
})
b.WriteByte('}')
return b.String()
}
// MarshalJSON implements json.Marshaler.
func (ls Labels) MarshalJSON() ([]byte, error) {
return json.Marshal(ls.Map())
}
// UnmarshalJSON implements json.Unmarshaler.
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
}
// MarshalYAML implements yaml.Marshaler.
func (ls Labels) MarshalYAML() (interface{}, error) {
return ls.Map(), nil
}
// UnmarshalYAML implements yaml.Unmarshaler.
func (ls *Labels) UnmarshalYAML(unmarshal func(interface{}) error) error {
var m map[string]string
if err := unmarshal(&m); err != nil {
return err
}
*ls = FromMap(m)
return nil
}
// IsValid checks if the metric name or label names are valid.
func (ls Labels) IsValid() bool {
err := ls.Validate(func(l Label) error {
if l.Name == model.MetricNameLabel && !model.IsValidMetricName(model.LabelValue(l.Value)) {
return strconv.ErrSyntax
}
if !model.LabelName(l.Name).IsValid() || !model.LabelValue(l.Value).IsValid() {
return strconv.ErrSyntax
}
return nil
})
return err == nil
}
// Map returns a string map of the labels.
func (ls Labels) Map() map[string]string {
m := make(map[string]string)
ls.Range(func(l Label) {
m[l.Name] = l.Value
})
return m
}
// 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...)
}
// NewBuilder returns a new LabelsBuilder.
func NewBuilder(base Labels) *Builder {
b := &Builder{
del: make([]string, 0, 5),
add: make([]Label, 0, 5),
}
b.Reset(base)
return b
}
// 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
}
// Keep removes all labels from the base except those with the given names.
func (b *Builder) Keep(ns ...string) *Builder {
b.base.Range(func(l Label) {
for _, n := range ns {
if l.Name == n {
return
}
}
b.del = append(b.del, l.Name)
})
return b
}
// Set the name/value pair as a label. A value of "" means delete that label.
func (b *Builder) Set(n, v string) *Builder {
if v == "" {
// Empty labels are the same as missing labels.
return b.Del(n)
}
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
}
func (b *Builder) Get(n string) string {
// Del() removes entries from .add but Set() does not remove from .del, so check .add first.
for _, a := range b.add {
if a.Name == n {
return a.Value
}
}
if slices.Contains(b.del, n) {
return ""
}
return b.base.Get(n)
}
// Range calls f on each label in the Builder.
func (b *Builder) Range(f func(l Label)) {
// Stack-based arrays to avoid heap allocation in most cases.
var addStack [128]Label
var delStack [128]string
// Take a copy of add and del, so they are unaffected by calls to Set() or Del().
origAdd, origDel := append(addStack[:0], b.add...), append(delStack[:0], b.del...)
b.base.Range(func(l Label) {
if !slices.Contains(origDel, l.Name) && !contains(origAdd, l.Name) {
f(l)
}
})
for _, a := range origAdd {
f(a)
}
}
func contains(s []Label, n string) bool {
for _, a := range s {
if a.Name == n {
return true
}
}
return false
}