Push promise-returning functions to the queue. Set the concurrency, and optionally a cooldown.
The queue is best understood as an airport runway: each function takes off with a minimum distance of the cooldown in milliseconds. Concurrency is the number of flights that can currently be in the air. When promises resolve, the plane has landed.
npm install housecall
var housecall = require('housecall');
var axios = require('axios');
var queue = housecall({ concurrency: 2, cooldown: 1000 });
queue.push(() => axios.get('https://twitter.com/').then((response, body) => {
// The eventual response of Twitter
}));
// This request will not start until 1000 ms after the above.
queue.push(() => axios.get('https://some.com/').then((response, body) => {
// ...
}));
// This will not run until of the above have terminated.
queue.push(() => axios.get('https://test.com/').then((response, body) => {
// ...
}));Make sure you wrap the function. Otherwise it will run immediately, and defeat the purpose of the queue.
// WILL NOT BE CORRECTLY ENQUEUED
queue.push(axios.get('https://twitter.com/').then((response, body) => {
// The queue will not control the start of execution here.
}));Whenever the queue is empty after handling tasks, it will emit an 'idle' event.
queue.on('idle', function(noTasksCompleted, noTasksWithError) {
// Do something
});The queue continues on any error, but the error will be outputted to stdout.