What is the best way to limit concurrency when using ES6's Promise.all()?

Question

I have some code that is iterating over a list that was queried out of a database and making an HTTP request for each element in that list. That list can sometimes be a rea

Answer 1

bluebird's Promise.map can take a concurrency option to control how many promises should be running in parallel. Sometimes it is easier than .all because you don't need to create the promise array.

const Promise = require('bluebird')

function getCounts() {
  return Promise.map(users, user => {
    return new Promise(resolve => {
      remoteServer.getCount(user) // makes an HTTP request
      .then(() => {
        /* snip */
        resolve();
       });
    });
  }, {concurrency: 10}); // <---- at most 10 http requests at a time
}