await-lock

What is await-lock?

The await-lock npm package provides a simple mechanism for managing asynchronous locks in JavaScript. It allows you to ensure that only one asynchronous operation can proceed at a time, which is useful for managing resources that should not be accessed concurrently.

What are await-lock's main functionalities?

Basic Locking

This feature allows you to create a lock and use it to ensure that a critical section of code is not executed concurrently by multiple asynchronous functions. The code sample demonstrates acquiring a lock before entering a critical section and releasing it afterward.

const AwaitLock = require('await-lock');
const lock = new AwaitLock();

async function criticalSection() {
  await lock.acquireAsync();
  try {
    // Perform operations that require exclusive access
  } finally {
    lock.release();
  }
}

async function run() {
  await Promise.all([criticalSection(), criticalSection()]);
}

run();

Try Lock

The try lock feature allows you to attempt to acquire a lock without waiting. If the lock is already held, the operation can proceed without blocking. This is useful for scenarios where you want to perform an operation only if it can be done immediately.

const lock = new AwaitLock();

async function tryLockExample() {
  if (lock.tryAcquire()) {
    try {
      // Perform operations that require exclusive access
    } finally {
      lock.release();
    }
  } else {
    console.log('Lock is already acquired by another operation.');
  }
}

tryLockExample();

Other packages similar to await-lock

async-mutex

The async-mutex package provides similar functionality to await-lock by offering mutexes for asynchronous code. It allows for more complex locking mechanisms, such as reentrant locks and read-write locks, which can be more flexible than the simple locks provided by await-lock.

semaphore-async-await

The semaphore-async-await package provides semaphore-based locking for asynchronous operations. Unlike await-lock, which provides a simple lock, this package allows you to control the number of concurrent operations, making it suitable for scenarios where you want to limit concurrency rather than enforce exclusivity.

README

AwaitLock

Mutex locks for async functions

API

API documentation

Usage

This package is published only as an ES module. In addition to importing ES modules from ES modules, modern versions of Node.js support requiring ES modules from CommonJS modules.

import AwaitLock from 'await-lock';

let lock = new AwaitLock();

async function runSerialTaskAsync() {
  await lock.acquireAsync();
  try {
    // IMPORTANT: Do not return a promise from here because the finally clause
    // may run before the promise settles, and the catch clause will not run if
    // the promise is rejected
  } finally {
    lock.release();
  }
}

You can also use AwaitLock with co and generator functions.

import AwaitLock from 'await-lock';

let runSerialTaskAsync = co.wrap(function*() {
  yield lock.acquireAsync();
  try {
    // Run async code in the critical section
  } finally {
    lock.release();
  }
});