@henrygd/queue

Tiny async queue with concurrency control. Like p-limit or fastq, but smaller and faster. See comparisons and benchmarks below.

Works with:

Usage

Create a queue with the newQueue function. Then add async functions - or promise returning functions - to your queue with the add method.

You can use queue.done() to wait for the queue to be empty.

import { newQueue } from '@henrygd/queue'

// create a new queue with a concurrency of 2
const queue = newQueue(2)

const pokemon = ['ditto', 'hitmonlee', 'pidgeot', 'poliwhirl', 'golem', 'charizard']

for (const name of pokemon) {
    queue.add(async () => {
        const res = await fetch(`https://pokeapi.co/api/v2/pokemon/${name}`)
        const json = await res.json()
        console.log(`${json.name}: ${json.height * 10}cm | ${json.weight / 10}kg`)
    })
}

console.log('running')
await queue.done()
console.log('done')

The return value of queue.add is the same as the return value of the supplied function.

const response = await queue.add(() => fetch('https://pokeapi.co/api/v2/pokemon'))
console.log(response.ok, response.status, response.headers)

Queue interface

/** Add an async function / promise wrapper to the queue */
queue.add<T>(promiseFunction: () => PromiseLike<T>): Promise<T>
/** Returns a promise that resolves when the queue is empty */
queue.done(): Promise<void>
/** Empties the queue (active promises are not cancelled) */
queue.clear(): void
/** Returns the number of promises currently running */
queue.active(): number
/** Returns the total number of promises in the queue */
queue.size(): number

Comparisons and benchmarks

Note on benchmarks

All libraries run the exact same test. Each operation measures how quickly the queue can resolve 1,000 async functions. The function just increments a counter and checks if it has reached 1,000.[^benchmark]

We check for completion inside the function so that promise-queue and p-limit are not penalized by having to use Promise.all (they don't provide a promise that resolves when the queue is empty).

Browser benchmark

This test was run in Chromium. Chrome and Edge are the same. Firefox and Safari are slower and closer, with @henrygd/queue just edging out promise-queue. I think both are hitting the upper limit of what those browsers will allow.

You can run or tweak for yourself here: https://jsbm.dev/TKyOdie0sbpOh

Node.js benchmarks

p-limit is very slow because it uses AsyncResource.bind on every run, which is much faster in Bun than in Node or Deno.

Ryzen 5 4500U | 8GB RAM | Node 22.3.0

Ryzen 7 6800H | 32GB RAM | Node 22.3.0

Deno benchmarks

Ryzen 5 4500U | 8GB RAM | Deno 1.44.4

Ryzen 7 6800H | 32GB RAM | Deno 1.44.4

Bun benchmarks

Ryzen 5 4500U | 8GB RAM | Bun 1.1.17

Ryzen 7 6800H | 32GB RAM | Bun 1.1.17

Cloudflare Workers benchmark

Uses oha to make 1,000 requests to each worker. Each request creates a queue and resolves 5,000 functions.

This was run locally using Wrangler on a Ryzen 7 6800H laptop. Wrangler uses the same workerd runtime as workers deployed to Cloudflare, so the relative difference should be accurate. Here's the repository for this benchmark.

Related

@henrygd/semaphore - Fastest javascript inline semaphores and mutexes using async / await.

License

MIT license

[^benchmark]: In reality, you may not be running so many jobs at once, and your jobs will take much longer to resolve. So performance will depend more on the jobs themselves.