khanhhua / async-lock

Async lock is a semaphore for Node

async-lock

async-lock is a semaphore for Node 6+ to prevent re-entrance in a single Node process.

Usage

Invoke lock then release

To lock a critical section, invoke the async lock() which returns a function to be invoked when the lock is ready to be released.

Assuming a function dbUpdateLikes with a critical section in module db.js

async function dbUpdateLikes(postId) {
    const post = await Post.findById(postId).exec();
    post.likes += 1;

    // Critical section
    await lock();

    await post.save();

    // End of critical section
    release();
    // Finishes of the function
}

and a http handler module routes.js

async function like(ctx) {
    // Do whatever here
    await db.dbUpdateLikes(ctx.params.postId)

    ctx.body = { ok: true };
}