prometheus/storage/remote/intern.go

101 lines
2.1 KiB
Go

// 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"
"sync/atomic"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
)
var interner = newPool()
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 {
s string
refs int64
}
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 {
atomic.AddInt64(&interned.refs, 1)
return interned.s
}
p.mtx.Lock()
defer p.mtx.Unlock()
if interned, ok := p.pool[s]; ok {
atomic.AddInt64(&interned.refs, 1)
return interned.s
}
p.pool[s] = &entry{
s: s,
refs: 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 := atomic.AddInt64(&interned.refs, -1)
if refs > 0 {
return
}
p.mtx.Lock()
defer p.mtx.Unlock()
if atomic.LoadInt64(&interned.refs) != 0 {
return
}
delete(p.pool, s)
}