mirror of https://github.com/prometheus/prometheus
104 lines
2.5 KiB
Go
104 lines
2.5 KiB
Go
// Copyright 2021 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package tsdbutil
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import (
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"errors"
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"fmt"
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"log/slog"
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"os"
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"path/filepath"
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"github.com/prometheus/client_golang/prometheus"
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tsdb_errors "github.com/prometheus/prometheus/tsdb/errors"
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"github.com/prometheus/prometheus/tsdb/fileutil"
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)
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const (
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lockfileDisabled = -1
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lockfileReplaced = 0
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lockfileCreatedCleanly = 1
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)
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type DirLocker struct {
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logger *slog.Logger
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createdCleanly prometheus.Gauge
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releaser fileutil.Releaser
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path string
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}
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// NewDirLocker creates a DirLocker that can obtain an exclusive lock on dir.
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func NewDirLocker(dir, subsystem string, l *slog.Logger, r prometheus.Registerer) (*DirLocker, error) {
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lock := &DirLocker{
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logger: l,
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createdCleanly: prometheus.NewGauge(prometheus.GaugeOpts{
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Name: fmt.Sprintf("prometheus_%s_clean_start", subsystem),
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Help: "-1: lockfile is disabled. 0: a lockfile from a previous execution was replaced. 1: lockfile creation was clean",
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}),
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}
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if r != nil {
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r.MustRegister(lock.createdCleanly)
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}
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lock.createdCleanly.Set(lockfileDisabled)
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absdir, err := filepath.Abs(dir)
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if err != nil {
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return nil, err
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}
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lock.path = filepath.Join(absdir, "lock")
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return lock, nil
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}
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// Lock obtains the lock on the locker directory.
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func (l *DirLocker) Lock() error {
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if l.releaser != nil {
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return errors.New("DB lock already obtained")
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}
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if _, err := os.Stat(l.path); err == nil {
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l.logger.Warn("A lockfile from a previous execution already existed. It was replaced", "file", l.path)
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l.createdCleanly.Set(lockfileReplaced)
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} else {
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l.createdCleanly.Set(lockfileCreatedCleanly)
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}
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lockf, _, err := fileutil.Flock(l.path)
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if err != nil {
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return fmt.Errorf("lock DB directory: %w", err)
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}
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l.releaser = lockf
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return nil
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}
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// Release releases the lock. No-op if the lock is not held.
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func (l *DirLocker) Release() error {
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if l.releaser == nil {
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return nil
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}
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errs := tsdb_errors.NewMulti()
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errs.Add(l.releaser.Release())
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errs.Add(os.Remove(l.path))
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l.releaser = nil
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return errs.Err()
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}
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