What causes "Unable to acquire file lock at path [{$this->path}]." in laravel/framework?

Retry the operation with backoff — locks are typically transient contention.

laravel/framework · warning · LockTimeoutException

Unable to acquire file lock at path [{$this->path}].

Error message

Unable to acquire file lock at path [{$this->path}].

What it means

Thrown by LockableFile::getSharedLock() when PHP's flock() with LOCK_SH fails (returns false). A shared (reader) lock cannot be acquired because another process holds an exclusive lock, or the underlying OS call failed. The exception (Illuminate\Contracts\Filesystem\LockTimeoutException) carries the file path so the contention point is identifiable. With $block=false (default) it uses LOCK_NB so it fails immediately rather than waiting.

Source

Thrown at src/Illuminate/Filesystem/LockableFile.php:134

        rewind($this->handle);

        ftruncate($this->handle, 0);

        return $this;
    }

    /**
     * Get a shared lock on the file.
     *
     * @param  bool  $block
     * @return $this
     *
     * @throws \Illuminate\Contracts\Filesystem\LockTimeoutException
     */
    public function getSharedLock($block = false)
    {
        if (! flock($this->handle, LOCK_SH | ($block ? 0 : LOCK_NB))) {
            throw new LockTimeoutException("Unable to acquire file lock at path [{$this->path}].");
        }

        $this->isLocked = true;

        return $this;
    }

    /**
     * Get an exclusive lock on the file.
     *
     * @param  bool  $block
     * @return $this
     *
     * @throws \Illuminate\Contracts\Filesystem\LockTimeoutException
     */
    public function getExclusiveLock($block = false)
    {
        if (! flock($this->handle, LOCK_EX | ($block ? 0 : LOCK_NB))) {

View on GitHub (pinned to bd6b5437e6)

Solutions

Retry the operation with backoff — locks are typically transient contention.
Pass block=true to wait blocking-style instead of failing fast, if a short wait is acceptable.
Ensure crashed workers release locks; clean stale lock files in storage/framework/cache or storage/framework/sessions.
Switch the cache/lock store from 'file' to 'redis' or 'database' for multi-worker workloads.
Verify the lock directory is on a local filesystem (not NFS) when using flock.

Example fix

// before
$lock = (new LockableFile($path, 'r'))->getSharedLock();

// after
use Illuminate\Contracts\Filesystem\LockTimeoutException;

try {
    $lock = (new LockableFile($path, 'r'))->getSharedLock(block: true);
} catch (LockTimeoutException $e) {
    // backoff and retry, or fall back to cache store
    usleep(100_000);
    return retry(3, fn () => (new LockableFile($path, 'r'))->getSharedLock(), 100);
}

Defensive patterns

Strategy: retry

Validate before calling

// No pure pre-check guarantees a lock is acquirable, but you can reduce contention:
if (! file_exists($path)) {
    abort(503, 'Lock target does not exist: '.$path);
}

Type guard

// No type guard applies to a runtime flock outcome; the relevant check is the exception type.
function isLockTimeout(\Throwable $e): bool {
    return $e instanceof \Illuminate\Contracts\Filesystem\LockTimeoutException;
}

Try / catch

use Illuminate\Contracts\Filesystem\LockTimeoutException;

try {
    $lock = (new \Illuminate\Filesystem\LockableFile($path, 'r'))->getSharedLock();
} catch (LockTimeoutException $e) {
    // retry with backoff, or pass block: true to wait
}

Prevention

Prefer Cache::lock() (redis/database) over file locks for multi-worker apps.
Keep critical sections short to minimize lock hold time.
Use block: true when a brief wait is acceptable to avoid immediate failure.
Avoid placing lock files on NFS/network filesystems.

When it happens

Trigger: Calling ->getSharedLock() on a LockableFile (used by cache stores, atomic file locks, debounce locks) while another worker holds an exclusive lock on the same path. Commonly reached through File cache driver, file-based locks with Cache::lock(), or concurrent queue workers reading a shared lock-protected resource.

Common situations: Multiple queue workers racing on the same cache file. Stale lock files left behind by a crashed worker. NFS/network filesystems where flock semantics are unreliable. High-concurrency local-cache setups during traffic spikes.

Related errors

AI-assisted analysis of laravel/framework@bd6b5437e6 (2026-08-06). Data as JSON: /data/errors/056faab9f8801173.json. Report an issue: GitHub.