qSem

This is another semaphore implementation for Node.js. It utilises native promises and has no dependencies to other modules.

API

Requiring the module returns a factory.

const qsem = require('qsem')(capacity);

The parameter capacity states the initial amount of tokens. If not specified it is set to 1.

Method: enter

qsem.enter().then(() => {...});

Returns a promise that resolves once tokens are available.

Method: leave

qsem.leave();

Increases the number of tokens and calls the next job if one is waiting in the queue.

Method: limit

qsem.limit(cb).then(() => {...});

Calls the method cb once tokens are available. If cb returns a Promise that is resolved or rejected, the number of available tokens is increased automatically. Don't call qsem.leave() inside of cb! qsem.limit() itself returns a promise that reflects the result of cb.