nextfile-js

nextfile

Atomic file-based locking with retry, TTL, heartbeat, PID tracking, stale detection, and multi-strategy support.

Installation

npm install nextfile

Quick Start

import { withLock, lock, lockSync } from 'nextfile';

// Wrap a function in a lock (auto-released)
await withLock('/tmp/my-resource', async () => {
  // only one process runs this at a time
});

// Manual acquire / release
const handle = await lock('/tmp/my-resource');
try {
  // critical section
} finally {
  await handle.release();
}

// Synchronous API
const { release } = lockSync('/tmp/my-resource');
release();

Features

Feature	Description
Atomic writes	Uses hard-link strategy — no partial writes
Multiple adapters	fs, atomic, mkdir, symlink
Multiple strategies	exclusive, shared, advisory, optimistic
TTL	Locks auto-expire after a configurable duration
Heartbeat	Refreshes lock timestamps to prevent false stale detection
PID tracking	Detects orphaned locks from dead processes
Stale detection	By age, PID liveness, or TTL expiry
Retry + backoff	linear, exponential, fibonacci, jitter
AbortSignal	Cancel acquisition at any point
Sync API	lockSync, unlockSync, checkSync
Events	Typed event system for monitoring
Hooks	Lifecycle hooks: beforeLock, afterLock, etc.
Middleware	Compose option transformers
CLI	lock, unlock, status, list, cleanup
TypeScript	100% typed, strict mode
ESM + CJS	Dual package

API

lock(path, options?) → Promise<LockHandle>

Acquire a lock. Retries with backoff on conflict.

const handle = await lock('/tmp/resource', {
  retries: 10,
  retryBackoff: 'exponential',
  ttl: 30_000,
  heartbeatInterval: 5_000,
  removeStale: true,
});
await handle.release();

withLock(path, fn, options?) → Promise<T>

Acquire, run fn, release — even on error.

const result = await withLock('/tmp/resource', async () => {
  return computeSomething();
});

lockSync(path, options?) → { lockPath, release }

Synchronous lock (no retry, no heartbeat).

checkLock(path) → Promise<LockFile>

Inspect a lock without acquiring it.

isLocked(path) → Promise<boolean>

Returns true if a non-stale lock exists.

cleanupLocks(dir, options?) → Promise<CleanupResult>

Remove stale lock files from a directory.

Options

Option	Type	Default	Description
retries	number	5	Max retry attempts
retryDelay	number	100	Base delay in ms
retryBackoff	string	'exponential'	Backoff strategy
retryMaxDelay	number	5000	Max delay cap in ms
timeout	number	60000	Total acquisition timeout
ttl	number	null	Lock TTL in ms
heartbeatInterval	number	5000	Heartbeat refresh interval
staleAge	number	30000	Age threshold for stale detection
removeStale	boolean	false	Auto-remove stale locks
strategy	string	'exclusive'	Lock strategy
adapter	string	'atomic'	File-system adapter
signal	AbortSignal	—	Cancellation signal
meta	object	{}	Arbitrary metadata stored in lock file

CLI

# Acquire a lock
nextfile lock /tmp/resource --ttl 30000

# Release a lock
nextfile unlock /tmp/resource

# Check status
nextfile status /tmp/resource --json

# List all locks in a directory
nextfile list --dir /tmp --recursive --table

# Clean up stale locks
nextfile cleanup --dir /tmp --stale-age 60000 --dry-run

Adapters

Adapter	Atomic	Cross-platform	Notes
atomic (default)	✅	✅	Hard-link strategy
fs	❌	✅	Simple wx flag write
mkdir	✅	✅	mkdir is atomic on most FS
symlink	✅	⚠️ Unix only	Symlink as lock token

Events

import { globalEmitter } from 'nextfile';

globalEmitter.on('acquired', (event) => {
  console.log('Lock acquired:', event.lockPath, 'after', event.elapsed, 'ms');
});

globalEmitter.on('stale', (event) => {
  console.warn('Stale lock detected:', event.lockPath);
});

Hooks

import { addBeforeLockHook, addAfterLockHook } from 'nextfile';

addBeforeLockHook(async (path, lockPath, options) => {
  console.log(`About to lock ${path}`);
});

addAfterLockHook(async (handle) => {
  console.log(`Acquired lock on ${handle.path}, PID ${handle.data.pid}`);
});

Middleware

import { withLoggingMiddleware, withRetryMiddleware, composeMiddleware } from 'nextfile';

const middleware = composeMiddleware(withLoggingMiddleware, withRetryMiddleware);
const handle = await lock('/tmp/resource', middleware({}));

License

MIT © nextfile contributors