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async-limiter

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async-limiter

asynchronous function queue with adjustable concurrency

    2.0.0latest

Version published
Maintainers
1
Weekly downloads
8,579,988
decreased by-21.47%

Weekly downloads

Changelog

Source

v2.0.0 (2019-11-20)

This release contains minor breaking changes. These changes should not affect most applications.

Breaking:
  • Jobs will not start until the next tick (process.nextTick) after the first job is added. This allows you to order multiple jobs synchronously without unexpected effects.

This should align the limiter closer to programmer expectations, but is technically breaking: the current code will immediately begin executing the first job as soon as it is pushed.

This change also fixes a few edge-case bugs related to ordering & sync jobs:

  • If an onDone() callback were added before any jobs were added in the same tick, it would be immediately called.
  • If a synchronous job were added, it would immediately execute completely and potentially call onDone().
Other changes:
  • Internals refactoring
  • Fix example calling start() (queue starts automatically)

Readme

Source

Async-Limiter

A module for limiting concurrent asynchronous actions in flight. Forked from queue.

npm tests coverage

This module exports a class Limiter that implements some of the Array API. Pass async functions (ones that accept a callback or return a promise) to an instance's additive array methods.

Motivation

Certain functions, like zlib, have undesirable behavior when run at infinite concurrency.

In this case, it is actually faster, and takes far less memory, to limit concurrency.

This module should do the absolute minimum work necessary to queue up functions. PRs are welcome that would make this module faster or lighter, but new functionality is not desired.

Style should confirm to nodejs/node style.

Example

var Limiter = require('async-limiter'); var t = new Limiter({ concurrency: 2 }); var results = []; // add jobs using the familiar Array API t.push(function(cb) { results.push('two'); cb(); }); t.push( function(cb) { results.push('four'); cb(); }, function(cb) { results.push('five'); cb(); } ); t.unshift(function(cb) { results.push('one'); cb(); }); t.splice(2, 0, function(cb) { results.push('three'); cb(); }); // Jobs run automatically on the next tick. // If you want a callback when all are done, call 'onDone()'. t.onDone(function() { console.log('all done:', results); });

Zlib Example

const zlib = require('zlib'); const Limiter = require('async-limiter'); const message = { some: 'data' }; const payload = new Buffer(JSON.stringify(message)); // Try with different concurrency values to see how this actually // slows significantly with higher concurrency! // // 5: 1398.607ms // 10: 1375.668ms // Infinity: 4423.300ms // const t = new Limiter({ concurrency: 5 }); function deflate(payload, cb) { t.push(function(done) { zlib.deflate(payload, function(err, buffer) { done(); cb(err, buffer); }); }); } console.time('deflate'); for (let i = 0; i < 30000; ++i) { deflate(payload, function(err, buffer) {}); } t.onDone(function() { console.timeEnd('deflate'); });

Install

npm install async-limiter

Test

npm test

API

var t = new Limiter([opts])

Constructor. opts may contain inital values for:

  • t.concurrency

Instance methods

t.onDone(fn)

fn will be called once and only once, when the queue is empty. If the queue is empty on the next tick, onDone() will be called.

Instance methods mixed in from Array

Mozilla has docs on how these methods work here.

t.push(element1, ..., elementN)

t.unshift(element1, ..., elementN)

t.splice(index , howMany[, element1[, ...[, elementN]]])

On the next tick, job processing will start.

Properties

t.concurrency

Max number of jobs the queue should process concurrently, defaults to Infinity.

t.length

Jobs pending + jobs to process (readonly).

Keywords

FAQs

What is async-limiter?

asynchronous function queue with adjustable concurrency

Is async-limiter popular?

The npm package async-limiter receives a total of 6,575,386 weekly downloads. As such, async-limiter popularity was classified as popular.

Is async-limiter well maintained?

We found that async-limiter demonstrated a not healthy version release cadence and project activity because the last version was released a year ago.It has 1 open source maintainer collaborating on the project.

Last updated on 20 Nov 2019
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