juicedata/juicefs · error

write lock file

Error message

write lock file %s: %w

What it means

Reported by diskCache.createLockFile when a new cache instance UUID cannot be persisted to the empty .lock file. The cache id would change across restarts, so the directory is marked problematic rather than silently reused.

Solutions

1. Ensure the cache directory is writable and the filesystem is healthy

When it happens

Trigger: Thrown at pkg/chunk/disk_cache.go:208 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of juicedata/juicefs@c9a67b23e8 (2026-09-06). Data as JSON: /api/errors/8283ea875548edaa. Report an issue: GitHub.

Appendix: source

Thrown at pkg/chunk/disk_cache.go:208

func (cache *diskCache) createLockFile() {
	lockfile := cache.lockFilePath()
	err := cache.checkErr(func() error {
		f, err := os.OpenFile(lockfile, os.O_CREATE|os.O_RDWR, 0666)
		if err != nil {
			return fmt.Errorf("open lock file %s: %w", lockfile, err)
		}
		defer f.Close()
		rawId, err := io.ReadAll(f)
		if err != nil {
			return fmt.Errorf("read lock file %s: %w", lockfile, err)
		}
		if len(rawId) > 0 {
			cache.id = string(rawId)
		} else {
			cache.id = uuid.New().String()
			_, err = f.Write([]byte(cache.id))
			if err != nil {
				return fmt.Errorf("write lock file %s: %w", lockfile, err)
			}
		}
		return nil
	})
	if err != nil {
		logger.Warnf("create lock file %s: %s", lockfile, err)
	}
}

func (cache *diskCache) checkLockFile() {
	lockfile := cache.lockFilePath()
	for cache.available() {
		time.Sleep(time.Second * 10)
		if err := cache.statFile(lockfile); err != nil && os.IsNotExist(err) {
			logger.Infof("lockfile %s is lost, cache device maybe broken", lockfile)
			if inRootVolume(cache.dir) && cache.freeRatio < 0.2 {
				logger.Infof("cache directory %s is in root volume, keep 20%% space free", cache.dir)
				cache.freeRatio = 0.2

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