blocking-promise-chain

blocking-promise-chain

A chain of promises that blocks when a limit is reached. This is useful in an async function to keep an outstanding number of promises running (to keep target busy). See below for examples:

Usage

Say you have a loop that's doing some external IO:

async function worker() {
  for (const data of allMyData) {
    await request.post(serverUrl, data);
  }
}

Nothing wrong here, except that the next post starts only when previous post is finished. To keep server fully busy, we should maintain a queue of outstanding requests. Using this module, code becomes:

import {BlockingPromiseChain} from 'blocking-promise-chain';
const MaxQueuedRequest = 10;

async function worker() {
  let chain = new BlockingPromiseChain(MaxQueuedRequest);
  for (const data of allMyData) {
    await chain.add(request.post(serverUrl, data));
  }
  await chain.flush();    // ensure all outstanding requests are finished
}

Simple as that.