prometheus/storage/remote/intern.go

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// Copyright 2019 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.
//
// Inspired / copied / modified from https://gitlab.com/cznic/strutil/blob/master/strutil.go,
// which is MIT licensed, so:
//
// Copyright (c) 2014 The strutil Authors. All rights reserved.
package remote
import (
"sync"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"go.uber.org/atomic"
)
var noReferenceReleases = promauto.NewCounter(prometheus.CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: "string_interner_zero_reference_releases_total",
Help: "The number of times release has been called for strings that are not interned.",
})
type pool struct {
mtx sync.RWMutex
pool map[string]*entry
}
type entry struct {
refs atomic.Int64
s string
}
func newEntry(s string) *entry {
return &entry{s: s}
}
func newPool() *pool {
return &pool{
pool: map[string]*entry{},
}
}
func (p *pool) intern(s string) string {
if s == "" {
return ""
}
p.mtx.RLock()
interned, ok := p.pool[s]
p.mtx.RUnlock()
if ok {
interned.refs.Inc()
return interned.s
}
p.mtx.Lock()
defer p.mtx.Unlock()
if interned, ok := p.pool[s]; ok {
interned.refs.Inc()
return interned.s
}
p.pool[s] = newEntry(s)
p.pool[s].refs.Store(1)
return s
}
func (p *pool) release(s string) {
p.mtx.RLock()
interned, ok := p.pool[s]
p.mtx.RUnlock()
if !ok {
noReferenceReleases.Inc()
return
}
refs := interned.refs.Dec()
if refs > 0 {
return
}
p.mtx.Lock()
defer p.mtx.Unlock()
if interned.refs.Load() != 0 {
return
}
delete(p.pool, s)
}
// used to create a lookup table for a new remote write request, should not be used concurrently
type lookupPool struct {
nextRef uint64
table map[uint64]string
reverseTable map[string]uint64
}
func newLookupPool() *lookupPool {
return &lookupPool{
table: map[uint64]string{},
reverseTable: map[string]uint64{},
}
}
func (p *lookupPool) intern(s string) uint64 {
if ref, ok := p.reverseTable[s]; ok {
return ref
}
ref := p.nextRef
p.reverseTable[s] = ref
p.table[ref] = s
p.nextRef++
return ref
}
func (p *lookupPool) getTable() map[uint64]string {
return p.table
}
func (p *lookupPool) clear() {
for k := range p.table {
delete(p.table, k)
}
for k := range p.reverseTable {
delete(p.reverseTable, k)
}
p.nextRef = 0
}