Queue-Jobs

A simple in-memory job queue with arbitrary concurrency.

Queue any number of jobs, execute n of them at a time, and by notified when the queue is empty.

Installation

# npm install queue-jobs

Quick usage

const Queue = require('queue-jobs');

const q = new Queue(3); // execute at most 3 jobs concurrently;

for (let i = 0; i < 100; i++ ) {
	q.do( () =>  // make sure your job returns a promise.
		doSomethingSlow(i)
		.then( () => { console.log('slow job done!') })
	);
}

q.whenDone()
.then( () => {
	console.log('all jobs completed!');
})

API

constructor()

new Queue(concurrency: number): Queue

Returns a new job queue that will run jobs with the specified concurrency.

Queue#do()

queue.do( job: () => Promise ): Promise

Schedules a job on the queue. Your job should return a promise; this is how the queue knows when it is finished.

Returns a promise that resolves when your job has been dispatched. This is useful for using in the _write method of a WritableStream implementation.

Queue#doSync()

queue.doAsync( job: () => any ): Promise

Schedules a job on the queue. Your job will be considered to be finished as soon as it returns (the queue won't wait for a returned promise to resolve).

Returns a promise that resolves when your job has been dispatched.

Queue#whenEmpty()

queue.whenEmpty(): Promise

Returns a promise that resolves when the queue has finished all jobs and no jobs remain to process. This only waits for the queue to be completely empty, it does not keep track of the jobs that were schedules when whenEmpty was called. To illustrate:

t = 0;

for (let i = 0; i < 50; i++ ) {
	queue.do( () =>
		doSomethingSlow(i)
		.then( () => {
			t++;
		})
	);
}

queue.whenEmpty()
.then( () => console.log(`t is ${t}`));

for (let i = 50; i < 100; i++ ) {
	queue.do( () =>
		doSomethingSlow(i)
		.then( () => {
			t++;
		})
	);
}

// prints 't is 100';