mirror of
https://github.com/offen/docker-volume-backup.git
synced 2024-09-19 21:20:28 +02:00
Frederik Ring
da8c63f755
* Retry on lock being unavailable * Refactor locking to return plain error * Collect LockedTime in stats * Add test case * Add documentation for LOCK_TIMEOUT * Log in case lock needs to be awaited * Release resources created for awaiting lock
59 lines
1.4 KiB
Go
59 lines
1.4 KiB
Go
// Copyright 2022 - Offen Authors <hioffen@posteo.de>
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// SPDX-License-Identifier: MPL-2.0
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package main
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import (
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"errors"
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"fmt"
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"time"
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"github.com/gofrs/flock"
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)
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// lock opens a lockfile at the given location, keeping it locked until the
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// caller invokes the returned release func. In case the lock is currently blocked
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// by another execution, it will repeatedly retry until the lock is available
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// or the given timeout is exceeded.
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func (s *script) lock(lockfile string) (func() error, error) {
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start := time.Now()
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defer func() {
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s.stats.LockedTime = time.Now().Sub(start)
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}()
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retry := time.NewTicker(5 * time.Second)
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defer retry.Stop()
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deadline := time.NewTimer(s.c.LockTimeout)
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defer deadline.Stop()
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fileLock := flock.New(lockfile)
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for {
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acquired, err := fileLock.TryLock()
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if err != nil {
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return noop, fmt.Errorf("lock: error trying lock: %w", err)
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}
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if acquired {
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if s.encounteredLock {
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s.logger.Info("Acquired exclusive lock on subsequent attempt, ready to continue.")
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}
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return fileLock.Unlock, nil
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}
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if !s.encounteredLock {
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s.logger.Infof(
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"Exclusive lock was not available on first attempt. Will retry until it becomes available or the timeout of %s is exceeded.",
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s.c.LockTimeout,
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)
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s.encounteredLock = true
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}
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select {
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case <-retry.C:
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continue
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case <-deadline.C:
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return noop, errors.New("lock: timed out waiting for lockfile to become available")
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}
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}
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}
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