Limits promises execution in order to reduce load.

Samples

import RequestLimiter from 'request-limiter';
import { inspect } from 'util';

const MAX_REQUEST = 2;
const REQUEST_NUMBER = 5;
const MIN_DELAY = 500;
const MAX_DELAY = 800;

async function main() {
    const expectedResults = [];
    for (let i = 0; i < REQUEST_NUMBER; i += 1) {
        expectedResults.push(`test#${i}`);
    }

    const requester = new RequestLimiter(MAX_REQUEST);
    console.log('execution');
    await Promise.all(expectedResults.map((one) => requester.add(() => {
        return new Promise((resolve) => setTimeout(() => {
            console.log(one, 'end');
            resolve(one);
        }, MIN_DELAY + Math.floor(Math.random() * (MAX_DELAY - MIN_DELAY))));
    })));
}

main()
    .then(() => process.exit(0))
    .catch((error) => {
        if (error instanceof Error || typeof error !== 'object') console.error(error);
    else inspect(error, false, null, true);
        process.exit(1);
    });

CHANGELOG

• 1.3.0
  • Now if a function passed to .add does not return a promise, an error is not thrown.
  • retry.immediately constructor option was removed

API

constructor(maxRequests: number, autoStart?: boolean, retry: {
  maxCount?: number;
  blockDelayFormula?: null | ((index: number) => number);
  immediately?: boolean;
});

---

public maxRequests: number Number of maximum active promises.

• Can be changed in progress

---

public autoStart: boolean If true, starts execution after the first add

• Default true

---

public retry.maxCount: number Max retries number

• Default 0

---

public retry.blockDelayFormula: null|((index: number) => number) Function accept retry index and returns delay to call next job

• Default 10 * (2 ** index)
• This parameter doesn't make any sense if retry.immediately is passed

---

add<T>(func: () => Promise<T>): Promise<T> Adds a promise function to execute queue.

• If you pass not a function that returns a promise, it will throw an error when executing the function

---

start(): Promise<void[]> Function to start execution

• Returns promises of jobs that have been started