limit-concurrency-decorator

limit-concurrency-decorator

Decorator to limit concurrency of async functions

Similar to these libraries, but can be used as decorator:

• throat
• p-limit

Also similar to p-concurrency, but the limit can be enforced over multiple functions.

Install

Installation of the npm package:

> npm install --save limit-concurrency-decorator

Usage

Simply apply the decorator to a method:

import { limitConcurrency } from "limit-concurrency-decorator"; class HttpClient { @limitConcurrency(2) get() { // ... } } const client = new HttpClient(); // these calls will run in parallel client.get("http://example.net/"); client.get("http://example2.net/"); // this call will wait for one of the 2 previous to finish client.get("http://example3.net/");

Or a simple function as a wrapper:

import httpRequest from "http-request-plus"; const httpRequestLimited = limitConcurrency(2)(httpRequest); // these calls will run in parallel httpRequestLimited("http://example.net/"); httpRequestLimited("http://example2.net/"); // this call will wait for one of the 2 previous to finish httpRequestLimited("http://example3.net/");

The limit can be shared:

const myLimit = limitConcurrency(2); class HttpClient { @myLimit post() { // ... } @myLimit put() { // ... } }

With FAIL_ON_QUEUE you can fail early instead of waiting:

import { FAIL_ON_QUEUE } from "limit-concurrency-decorator"; try { await httpRequestLimited(FAIL_ON_QUEUE, "http://example2.net"); } catch (error) { error.message; // 'no available place in queue' }

Custom termination:

const httpRequestLimited = limitConcurrency(2, async promise => { const stream = await promise; await new Promise(resolve => { stream.on("end", resolve); stream.on("error", reject); }); })(httpRequest); // these calls will run in parallel httpRequestLimited("http://example.net/"); httpRequestLimited("http://example2.net/"); // this call will wait for one of the 2 previous responses to have been read entirely httpRequestLimited("http://example3.net/");

Contributions

Contributions are very welcomed, either on the documentation or on the code.

You may:

• report any issue you've encountered;
• fork and create a pull request.

License

ISC © Julien Fontanet