zz-pool

A promise pool implementation to limit concurrency.

This can be useful for example if you want to limit the number of HTTP requests that can be in-flight simultaneously:

const Pool = require('zz-pool');
const fetch = require('node-fetch');

const pool = new Pool(10); // create a pool of size 10

async function fetchUrl(url) {
  const response = await pool.enqueue(() => fetch(url));
  return response;
}

You can enqueue many requests on the pool, but the 11th won't start until the first finishes. Only 10 are allowed to run simultaneously.

API

const pool = new Pool(size)

Create a pool that only allows size simultaneous asynchronous operations.

pool.enqueue(promiseFunc)

Enqueue an operation. The promiseFunc argument should be a function that returns a promise. enqueue returns a promise that resolves or rejects with the result of the promise returned by your promiseFunc.