async-locks

The thread like locks in async functions

Why

Async functions are somehow alike with multi-thread solutions. So you may need a lock to resolve the conflicts between async functions.

const lock = new Lock();

async append(text) {
    await lock.acquire();
    let originalText = await getText();
    await setText(originalText + text);
    lock.release();
}

Promise.all(append('FOO'), append('BAR'))

Timeout

If timeout is set, the lock will be released automatically when time is out, to avoid the case that locks never get released.

async append(text) {
    await lock.acquire({timeout: 10000});
    await neverResponse();    // neverResponse returns a promise with resolve/reject never called. We should avoid
                              // this case from happening, but also we can add a timeout to make the code stronger.
    lock.release();
}

Limit

If limit is set a positive integer, the lock will not block unless the unreleased number reached the limit.

const lock = new Lock({limit: 10});

async test() {
    while (true) {
        await lock.acquire();   // will get blocked at the 11 times loop
    }
}