prometheus/tsdb/tsdbutil/dir_locker.go

105 lines
2.6 KiB
Go

// Copyright 2021 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 tsdbutil
import (
"errors"
"fmt"
"os"
"path/filepath"
"github.com/go-kit/log"
"github.com/go-kit/log/level"
"github.com/prometheus/client_golang/prometheus"
tsdb_errors "github.com/prometheus/prometheus/tsdb/errors"
"github.com/prometheus/prometheus/tsdb/fileutil"
)
const (
lockfileDisabled = -1
lockfileReplaced = 0
lockfileCreatedCleanly = 1
)
type DirLocker struct {
logger log.Logger
createdCleanly prometheus.Gauge
releaser fileutil.Releaser
path string
}
// NewDirLocker creates a DirLocker that can obtain an exclusive lock on dir.
func NewDirLocker(dir, subsystem string, l log.Logger, r prometheus.Registerer) (*DirLocker, error) {
lock := &DirLocker{
logger: l,
createdCleanly: prometheus.NewGauge(prometheus.GaugeOpts{
Name: fmt.Sprintf("prometheus_%s_clean_start", subsystem),
Help: "-1: lockfile is disabled. 0: a lockfile from a previous execution was replaced. 1: lockfile creation was clean",
}),
}
if r != nil {
r.MustRegister(lock.createdCleanly)
}
lock.createdCleanly.Set(lockfileDisabled)
absdir, err := filepath.Abs(dir)
if err != nil {
return nil, err
}
lock.path = filepath.Join(absdir, "lock")
return lock, nil
}
// Lock obtains the lock on the locker directory.
func (l *DirLocker) Lock() error {
if l.releaser != nil {
return errors.New("DB lock already obtained")
}
if _, err := os.Stat(l.path); err == nil {
level.Warn(l.logger).Log("msg", "A lockfile from a previous execution already existed. It was replaced", "file", l.path)
l.createdCleanly.Set(lockfileReplaced)
} else {
l.createdCleanly.Set(lockfileCreatedCleanly)
}
lockf, _, err := fileutil.Flock(l.path)
if err != nil {
return fmt.Errorf("lock DB directory: %w", err)
}
l.releaser = lockf
return nil
}
// Release releases the lock. No-op if the lock is not held.
func (l *DirLocker) Release() error {
if l.releaser == nil {
return nil
}
errs := tsdb_errors.NewMulti()
errs.Add(l.releaser.Release())
errs.Add(os.Remove(l.path))
l.releaser = nil
return errs.Err()
}