promise-queue-timeout

promise queue with option to limit new task start time with timeout

Install

• yarn:

yarn add @shelex/promise-queue-timeout

• npm:

npm install @shelex/promise-queue-timeout

Usage

import Queue from '@shelex/promise-queue-timeout';
// const Queue = require("@shelex/promise-queue-timeout")

const runner = new Queue({
    executors: 2,
    timeout: 2000 // ms
});

runner.enqueue(task, 'A'); // starts automatically
runner.enqueue(task, 'B'); // will be started after 2000ms
runner.enqueue(task, 'C'); // will be started when A or B finished, but after 2000ms from previous start

runner.on('resolve', (data) => console.log(data));
runner.on('reject', (error) => console.error(error));

runner.on('end', () =>
    console.log(`queue finished, all enqueued tasks processed`)
);

API

const q = Queue({options})

Constructor. options may contain inital values for:

• q.executors, default: 2; number of tasks executed
• q.timeout, default: 1000; number of ms after previous task start time

q.enqueue(task, id)

Add a task to queue which immediately starts processing.
Task is a function that returns a promise. Id is optional.

q.stop()

Stops the queue and clears tasks backlog. can be resumed with enqueuing new taks.

q.next()

Returns resolved value for next executed task

q.on('start')

queue started tasks processing

q.on('end')

queue processed all tasks

q.on('stop')

queue stopped processing current tasks and cleared backlog

q.on('starting_task', (id, remainingTasksCount))

queue starting task. Callback has task ID and remaining counter for tasks backlog

q.on('resolve', value)

returns value resolved for just executed task

q.on('reject', err)

returns err for rejected promise for just executed task

q.on('next')

queue is selecting next task from backlog

Motivation

This queue is an attempt to solve issue with parallelizing testing engines which are fighting for shared resources on initialization, so adding a timeout after start would allow to limit such concurrent startup.

License

Copyright © 2020 Oleksandr Shevtsov [email protected]

This work is free. You can redistribute it and/or modify it under the terms of the MIT License. See LICENSE for full details.