firework

A distributed, fault-tolerant work queue for Firebase

npm install firework
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Firework is a distributed, fault-tolerant work queue for Firebase.

Creating Jobs

Since you're using Firebase, you'll probably want to create jobs directly from the browser. To do this, setup a new Firebase location reference that will serve as your queue. To start, you may want to make sure that this location is writable by everyone but only readable by your server (i.e. worker) process.

In this example, we'll assume that your queue is located at https://my-firebase.firebaseio.com/myQueue. In your client code, you'll want to create a new child of the pendingJobs child of that location reference, like so:

var jobs = new Firebase('https://my-firebase.firebaseio.com/myQueue/pendingJobs');
jobs.push({ my: 'job' });

That's it. You've now pushed a job onto the queue for a worker to process sometime later.

It should be noted that workers pull from the beginning of the queue (FIFO). If you have jobs of varying importance you can use a priority to run some jobs before others.

jobs.push().setWithPriority({ important: 'job' }, 0);
jobs.push().setWithPriority({ less: 'important' }, 100);

Firework also provides an API for creating jobs from within your server process. A Firework.Queue (see Processing Jobs below) has a push method for this purpose.

var firework = require('firework');
var queue = new firework.Queue('https://my-firebase.firebaseio.com/myQueue');
queue.push({ my: 'job' });

Important: The following job property names are reserved:

  • _name
  • _startedAt
  • _succeededAt
  • _failedAt
  • _error

Processing Jobs

The easiest way to start processing the jobs on a Firework queue is to use the firework command:

$ firework create-worker.js -w 5

The -w argument specifies the number of workers to use. When a worker has an unrecoverable error it is removed from the worker pool and replaced with a new one.

The create-worker.js module that you pass to firework should export a function that is used to create new workers. To process jobs from the queue we pushed onto in the Creating Jobs section above, our create-worker.js file could look something like this:

var firework = require('firework');
var queue = new firework.Queue('https://my-firebase.firebaseio.com/myQueue');

module.exports = function () {
  return new firework.Worker(queue, function (job, callback) {
    // process the given job.

    // call the callback when you're done, optionally with
    // any error that was encountered while doing the work.
    callback(error);
  });
};

When Firework is done processing a job it stores the job along with some metadata in the startedJobs child location of your queue. Thus, pendingJobs contains a list of all jobs that still need to be done and startedJobs contains a list of all jobs that you have attempted.

Retrying Failed Jobs

If a job fails, it will have _failedAt and _error properties. You can use the _error property to determine the reason of the failure. Once you've fixed the problem, you can retry all jobs that failed using:

queue.retryFailedJobs();

Installation

You can install Firework using npm:

$ npm install firework

Tests

To run the tests, do:

$ npm install
$ mocha

License

MIT

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