promise-kue

If you wanna limit promise concurrency, the library could help you.

Introduction

Sometimes we have a lot of promises to execute. If we run them at the same time, resource would be used up. So we need to limit number of running promises.

Installation

$ npm install promise-kue

Usage

First create a job queue with two parameters: limit and max. limit is the number of concurrency promise. max is the max number of tasks waiting in queue. And max would be default value 2000 if you don't pass it:

const {createQueue, Task} = require('promise-kue')

const queue = createQueue(5, 1000)

Then you could write a method wraping Promise. This is used for delaying execution:

function asynchronousFunc (arg1, arg2, ...) {
	return new Promise((resolve, reject) => {
		//...
	}
}

Construct tasks to execute:

const tasks1 = [
  new Task(asynchronousFunc, [arg1, arg2...]),
  new Task(asynchronousFunc, [arg1, arg2...]),
  //...
]

const tasks2 = [
	new Task(asynchronousFunc, [arg1, arg2...]),
  new Task(asynchronousFunc, [arg1, arg2...]),
  //...
]

The last step is just pushing tasks to queue and waiting for results.

queue.on(queue.push(tasks1), (err, result) => {
  //...
})
//Using head method to push tasks to the head of queue.
queue.on(queue.head(tasks1), (err, result) => {
  //...
})
//Could also push only one task to queue.
queue.on(queue.head(new Task(asynchronousFunc, [arg1, arg2...])), (err, result) => {
  //...
})

If queue is not overloaded, result would have two properties: success and failure. They are both arrays containing successful results and fail results. But order is not guaranteed.

Any suggestions is welcome.

License

This project is licensed under the MIT license. See the LICENSE file for more info.