pause-queue

A queue for Node.js that can be paused and resumed.

This can become useful if you want to stop processing when a resource becomes unavailable and continue execution when it's available again. Or what ever you can imagine.

Installation

npm install pause-queue --save

Or manually add it to your package.json

Example

var pausequeue = require('pause-queue'),
  i = 0,
  start = +Date.now()
  animals = [
    'Aardvark', 'Albatross',
    'Alligator', 'Alpaca', 'Ant',
    'Anteater', 'Antelope', 'Ape',
    'Armadillo', 'Donkey', 'Baboon',
    'Badger', 'Barracuda', 'Bat', 
    'Bear', 'Beaver', 'Bee', 'Bison',
    'Buffalo' ];

// Helper function to show the time difference
function since (time) { return Math.round((time - start) / 1000) + 's'; }

// Create a new queue. The first argument is the worker, the second is the concurrency (default: 1)
var animalQueue = pausequeue(function (animal, done) {
  console.log(animal, since(+Date.now()));
  done(); // don't forget
}, 1);

// Pause the queue after 4 seconds
setTimeout(function () {
  animalQueue.pause();
}, 4000);

// Resume the queue after 10 seconds
setTimeout(function () {
  animalQueue.resume();
}, 10000);


// Add a new animal to the queue every second until all animals are added
var interval = setInterval(function () {
  if (i === animals.length) { return clearInterval(interval); }
  animalQueue.push(animals[i]);
  i++;
}, 1000);

Output:

Aardvark 1s
Albatross 2s
Alligator 3s  // ...now waiting for 6 seconds
Alpaca 10s
Ant 10s
Anteater 10s
Antelope 10s
Ape 10s
Armadillo 10s
Donkey 10s
Baboon 11s
Badger 12s
Barracuda 13s
Bat 14s
Bear 15s
Beaver 16s
Bee 17s
Bison 18s
Buffalo 19s

License

MIT License

Copyright (c) 2011 Max Kueng (http://maxkueng.com/)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.