# fastq ![ci][ci-url] [![npm version][npm-badge]][npm-url] [![Dependency Status][david-badge]][david-url] Fast, in memory work queue. Benchmarks (1 million tasks): * setImmediate: 812ms * fastq: 854ms * async.queue: 1298ms * neoAsync.queue: 1249ms Obtained on node 12.16.1, on a dedicated server. If you need zero-overhead series function call, check out [fastseries](http://npm.im/fastseries). For zero-overhead parallel function call, check out [fastparallel](http://npm.im/fastparallel). [![js-standard-style](https://raw.githubusercontent.com/feross/standard/master/badge.png)](https://github.com/feross/standard) * Installation * Usage * API * Licence & copyright ## Install `npm i fastq --save` ## Usage (callback API) ```js 'use strict' const queue = require('fastq')(worker, 1) queue.push(42, function (err, result) { if (err) { throw err } console.log('the result is', result) }) function worker (arg, cb) { cb(null, arg * 2) } ``` ## Usage (promise API) ```js const queue = require('fastq').promise(worker, 1) async function worker (arg) { return arg * 2 } async function run () { const result = await queue.push(42) console.log('the result is', result) } run() ``` ### Setting "this" ```js 'use strict' const that = { hello: 'world' } const queue = require('fastq')(that, worker, 1) queue.push(42, function (err, result) { if (err) { throw err } console.log(this) console.log('the result is', result) }) function worker (arg, cb) { console.log(this) cb(null, arg * 2) } ``` ### Using with TypeScript (callback API) ```ts 'use strict' import * as fastq from "fastq"; import type { queue, done } from "fastq"; type Task = { id: number } const q: queue = fastq(worker, 1) q.push({ id: 42}) function worker (arg: Task, cb: done) { console.log(arg.id) cb(null) } ``` ### Using with TypeScript (promise API) ```ts 'use strict' import * as fastq from "fastq"; import type { queueAsPromised } from "fastq"; type Task = { id: number } const q: queueAsPromised = fastq.promise(asyncWorker, 1) q.push({ id: 42}).catch((err) => console.error(err)) async function asyncWorker (arg: Task): Promise { // No need for a try-catch block, fastq handles errors automatically console.log(arg.id) } ``` ## API * fastqueue() * queue#push() * queue#unshift() * queue#pause() * queue#resume() * queue#idle() * queue#length() * queue#getQueue() * queue#kill() * queue#killAndDrain() * queue#error() * queue#concurrency * queue#drain * queue#empty * queue#saturated * fastqueue.promise() ------------------------------------------------------- ### fastqueue([that], worker, concurrency) Creates a new queue. Arguments: * `that`, optional context of the `worker` function. * `worker`, worker function, it would be called with `that` as `this`, if that is specified. * `concurrency`, number of concurrent tasks that could be executed in parallel. ------------------------------------------------------- ### queue.push(task, done) Add a task at the end of the queue. `done(err, result)` will be called when the task was processed. ------------------------------------------------------- ### queue.unshift(task, done) Add a task at the beginning of the queue. `done(err, result)` will be called when the task was processed. ------------------------------------------------------- ### queue.pause() Pause the processing of tasks. Currently worked tasks are not stopped. ------------------------------------------------------- ### queue.resume() Resume the processing of tasks. ------------------------------------------------------- ### queue.idle() Returns `false` if there are tasks being processed or waiting to be processed. `true` otherwise. ------------------------------------------------------- ### queue.length() Returns the number of tasks waiting to be processed (in the queue). ------------------------------------------------------- ### queue.getQueue() Returns all the tasks be processed (in the queue). Returns empty array when there are no tasks ------------------------------------------------------- ### queue.kill() Removes all tasks waiting to be processed, and reset `drain` to an empty function. ------------------------------------------------------- ### queue.killAndDrain() Same than `kill` but the `drain` function will be called before reset to empty. ------------------------------------------------------- ### queue.error(handler) Set a global error handler. `handler(err, task)` will be called each time a task is completed, `err` will be not null if the task has thrown an error. ------------------------------------------------------- ### queue.concurrency Property that returns the number of concurrent tasks that could be executed in parallel. It can be altered at runtime. ------------------------------------------------------- ### queue.drain Function that will be called when the last item from the queue has been processed by a worker. It can be altered at runtime. ------------------------------------------------------- ### queue.empty Function that will be called when the last item from the queue has been assigned to a worker. It can be altered at runtime. ------------------------------------------------------- ### queue.saturated Function that will be called when the queue hits the concurrency limit. It can be altered at runtime. ------------------------------------------------------- ### fastqueue.promise([that], worker(arg), concurrency) Creates a new queue with `Promise` apis. It also offers all the methods and properties of the object returned by [`fastqueue`](#fastqueue) with the modified [`push`](#pushPromise) and [`unshift`](#unshiftPromise) methods. Node v10+ is required to use the promisified version. Arguments: * `that`, optional context of the `worker` function. * `worker`, worker function, it would be called with `that` as `this`, if that is specified. It MUST return a `Promise`. * `concurrency`, number of concurrent tasks that could be executed in parallel. #### queue.push(task) => Promise Add a task at the end of the queue. The returned `Promise` will be fulfilled (rejected) when the task is completed successfully (unsuccessfully). This promise could be ignored as it will not lead to a `'unhandledRejection'`. #### queue.unshift(task) => Promise Add a task at the beginning of the queue. The returned `Promise` will be fulfilled (rejected) when the task is completed successfully (unsuccessfully). This promise could be ignored as it will not lead to a `'unhandledRejection'`. #### queue.drained() => Promise Wait for the queue to be drained. The returned `Promise` will be resolved when all tasks in the queue have been processed by a worker. This promise could be ignored as it will not lead to a `'unhandledRejection'`. ## License ISC [ci-url]: https://github.com/mcollina/fastq/workflows/ci/badge.svg [npm-badge]: https://badge.fury.io/js/fastq.svg [npm-url]: https://badge.fury.io/js/fastq [david-badge]: https://david-dm.org/mcollina/fastq.svg [david-url]: https://david-dm.org/mcollina/fastq

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