Bull Job Manager

A lightweight, robust and fast job processing queue. Carefully written for rock solid stability and atomicity.

It uses redis for persistence, so the queue is not lost if the server goes down for any reason.

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Features:

• Minimal CPU usage by poll free design.
• Robust design based on Redis.
• Delayed jobs.
• Retries.
• Priority.
• Concurrency.
• Global pause/resume.

Install:

npm install bull

Note that you need a redis version higher or equal than 2.8.11 for bull to work properly.

Quick Guide

var Queue = require('bull');

var videoQueue = Queue('video transcoding', 6379, '127.0.0.1');
var audioQueue = Queue('audio transcoding', 6379, '127.0.0.1');
var imageQueue = Queue('image transcoding', 6379, '127.0.0.1');

videoQueue.process(function(job, done){

  // job.data contains the custom data passed when the job was created
  // job.jobId contains id of this job.

  // transcode video asynchronously and report progress
  job.progress(42);

  // call done when finished
  done();

  // or give a error if error
  done(Error('error transcoding'));
  
  // or pass it a result
  done(null, { framerate: 29.5 /* etc... */ });

  // If the job throws an unhandled exception it is also handled correctly
  throw (Error('some unexpected error'));
});

audioQueue.process(function(job, done){
  // transcode audio asynchronously and report progress
  job.progress(42);

  // call done when finished
  done();

  // or give a error if error
  done(Error('error transcoding'));
  
  // or pass it a result
  done(null, { samplerate: 48000 /* etc... */ });

  // If the job throws an unhandled exception it is also handled correctly
  throw (Error('some unexpected error'));
});

imageQueue.process(function(job, done){
  // transcode image asynchronously and report progress
  job.progress(42);

  // call done when finished
  done();

  // or give a error if error
  done(Error('error transcoding'));
  
  // or pass it a result
  done(null, { width: 1280, height: 720 /* etc... */ });

  // If the job throws an unhandled exception it is also handled correctly
  throw (Error('some unexpected error'));
});

videoQueue.add({video: 'http://example.com/video1.mov'});
audioQueue.add({audio: 'http://example.com/audio1.mp3'});
imageQueue.add({image: 'http://example.com/image1.tiff'});

Alternatively, you can use return promises instead of using the done callback:

videoQueue.process(function(job){ // don't forget to remove the done callback!
  // Simply return a promise
  return fetchVideo(job.data.url).then(transcodeVideo);

  // Handles promise rejection
  return Promise.reject(new Error('error transcoding'));

  // Passes the value the promise is resolved with to the "completed" event 
  return Promise.resolve({ framerate: 29.5 /* etc... */ });

  // If the job throws an unhandled exception it is also handled correctly
  throw new Error('some unexpected error');
  // same as
  return Promise.reject(new Error('some unexpected error'));
});

A queue can be paused and resumed:

queue.pause().then(function(){
  // queue is paused now
});

queue.resume().then(function(){
  // queue is resumed now
})

A queue emits also some useful events:

.on('ready', function() {
  // Queue ready for job
  // All Redis connections are done
})
.on('error', function(error) {
  // Error
})
.on('active', function(job, jobPromise){
  // Job started
  // You can use jobPromise.cancel() to abort this job.
})
.on('progress', function(job, progress){
  // Job progress updated!
})
.on('completed', function(job, result){
  // Job completed with output result!
})
.on('failed', function(job, err){
  // Job failed with reason err!
})
.on('paused', function(){
  // The queue has been paused
})
.on('resumed', function(job){
  // The queue has been resumed
})
.on('cleaned', function(jobs, type) {
  //jobs is an array of cleaned jobs
  //type is the type of job cleaned
  //see clean for details
});

Queues are cheap, so if you need many of them just create new ones with different names:

var userJohn = Queue('john');
var userLisa = Queue('lisa');
.
.
.

Queues are robust and can be run in parallel in several threads or processes without any risk of hazards or queue corruption. Check this simple example using cluster to parallelize jobs across processes:

var
  Queue = require('bull'),
  cluster = require('cluster');

var numWorkers = 8;
var queue = Queue("test concurrent queue", 6379, '127.0.0.1');

if(cluster.isMaster){
  for (var i = 0; i < numWorkers; i++) {
    cluster.fork();
  }

  cluster.on('online', function(worker) {
    // Lets create a few jobs for the queue workers
    for(var i=0; i<500; i++){
      queue.add({foo: 'bar'});
    };
  });

  cluster.on('exit', function(worker, code, signal) {
    console.log('worker ' + worker.process.pid + ' died');
  });
}else{
  queue.process(function(job, jobDone){
    console.log("Job done by worker", cluster.worker.id, job.jobId);
    jobDone();
  });
}

Useful patterns

####Message Queue

Bull can also be used for persistent message queues. This is a quite useful feature in some usecases. For example, you can have two servers that need to communicate with each other. By using a queue the servers do not need to be online at the same time, this create a very robust communication channel. You can treat add as send and process as receive:

Server A:

var Queue = require('bull');

var sendQueue = Queue("Server B");
var receiveQueue = Queue("Server A");

receiveQueue.process(function(msg, done){
  console.log("Received message", msg);
  done();
});

sendQueue.add({msg:"Hello"});

Server B:

var Queue = require('bull');

var sendQueue = Queue("Server A");
var receiveQueue = Queue("Server B");

receiveQueue.process(function(msg, done){
  console.log("Received message", msg);
  done();
});

sendQueue.add({msg:"World"});

####Returning job completions

A common pattern is where you have a cluster of queue processors that just process jobs as fast as they can, and some other services that need to take the result of this processors and do something with it, maybe storing results in a database.

The most robust and scalable way to accomplish this is by combining the standard job queue with the message queue pattern: a service sends jobs to the cluster just by opening a job queue and adding jobs to it, the cluster will start processing as fast as it can. Everytime a job gets completed in the cluster a message is send to a results message queue with the result data, this queue is listened by some other service that stores the results in a database.

##Documentation

• Queue
• Queue##process
• Queue##add
• Queue##pause
• Queue##resume
• Queue##count
• Queue##empty
• Queue##clean
• Queue##close
• Job
• Job##remove

Reference

###Queue(queueName, redisPort, redisHost, [redisOpts])

This is the Queue constructor. It creates a new Queue that is persisted in Redis. Everytime the same queue is instantiated it tries to process all the old jobs that may exist from a previous unfinished session.

Arguments

    queueName {String} A unique name for this Queue.
    redisPort {Number} A port where redis server is running.
    redisHost {String} A host specified as IP or domain where redis is running.
    redisOptions {Object} Options to pass to the redis client. https://github.com/mranney/node_redis

---

#### Queue##process([concurrency,] function(job[, done]))

Defines a processing function for the jobs placed into a given Queue.

The callback is called everytime a job is placed in the queue. It is passed an instance of the job as first argument.

If the callback signature contains the second optional done argument, the callback will be passed a done callback to be called after the job has been completed. The done callback can be called with an Error instance, to signal that the job did not complete successfully, or with a result as second argument as second argument (e.g.: done(null, result);) when the job is successful. Errors will be passed as a second argument to the "failed" event; results, as a second argument to the "completed" event.

If, however, the callback signature does not contain the done argument, a promise must be returned to signal job completion. If the promise is rejected, the error will be passed as a second argument to the "failed" event. If it is resolved, its value will be the "completed" event's second argument.

Note: in order to determine whether job completion is signaled by returning a promise or calling the done callback, Bull looks at the length property of the callback you pass to it. So watch out, as the following won't work:

// THIS WON'T WORK!!
queue.process(function(job, done) { // Oops! done callback here!
    return Promise.resolve();
});

This, however, will:

queue.process(function(job) { // No done callback here :)
    return Promise.resolve();
});

You can specify a concurrency. Bull will then call you handler in parallel respecting this max number.

Arguments

    job {String} The job to process.
    done {Function} The done callback to be called after the job has been completed.

---

#### Queue##add(data, opts)

Creates a new job and adds it to the queue. If the queue is empty the job will be executed directly, otherwise it will be placed in the queue and executed as soon as possible.

Arguments

  data {PlainObject} A plain object with arguments that will be passed
    to the job processing function in job.data.
  opts {PlainObject} A plain object with arguments that will be passed
    to the job processing function in job.opts
  opts.delay {Number} An amount of miliseconds to wait until this job
  can be processed. Note that for accurate delays, both server and clients
  should have their clocks synchronized. [optional]
  opts.attempts {Number} A number of attempts to retry if the job fails [optional]
  opts.backoff {Number|Object} Backoff setting for automatic retries if the job fails
  opts.backoff.type {String} Backoff type, which can be either `fixed` or `exponential`
  opts.backoff.delay {String} Backoff delay, in milliseconds
  opts.lifo {Boolean} A boolean which, if true, adds the job to the right
    of the queue instead of the left (default false)
  opts.timeout {Number} The number of milliseconds after which the job
    should be fail with a timeout error [optional]
  returns {Promise} A promise that resolves when the job has been succesfully
    added to the queue (or rejects if some error occured). On success, the promise
    resolves to the new Job.

---

#### Queue##pause()

Returns a promise that resolves when the queue is paused. The pause is global, meaning that all workers in all queue instances for a given queue will be paused. A paused queue will not process new jobs until resumed, but current jobs being processed will continue until they are finalized.

Pausing a queue that is already paused does nothing.

Arguments

  returns {Promise} A promise that resolves when the queue is paused.

---

#### Queue##resume()

Returns a promise that resolves when the queue is resumed after being paused. The resume is global, meaning that all workers in all queue instances for a given queue will be resumed.

Resuming a queue that is not paused does nothing.

Arguments

  returns {Promise} A promise that resolves when the queue is resumed.

---

#### Queue##count()

Returns a promise that returns the number of jobs in the queue, waiting or paused. Since there may be other processes adding or processing jobs, this value may be true only for a very small amount of time.

Arguments

  returns {Promise} A promise that resolves with the current jobs count.

---

#### Queue##empty()

Empties a queue deleting all the input lists and associated jobs.

Arguments

  returns {Promise} A promise that resolves with the queue is emptied.

---

#### Queue##close() Closes the underlying redis client. Use this to perform a graceful shutdown.

var Queue = require('bull');
var queue = Queue('example');

var after100 = _.after(100, function () {
  queue.close().then(function () { console.log('done') })
});

queue.on('completed', after100);

close can be called from anywhere, with one caveat: if called from within a job handler the queue won't close until after the job has been processed, so the following won't work:

queue.process(function (job, jobDone) {
  handle(job);
  queue.close().then(jobDone);
});

Instead, do this:

queue.process(function (job, jobDone) {
  handle(job);
  queue.close();
  jobDone();
});

Or this:

queue.process(function (job) {
  queue.close();
  return handle(job).then(...);
});

Arguments

  returns {Promise} A promise that resolves when the redis client closes.

---

#### Queue##getJob(jobId)

Returns a promise that will return the job instance associated with the jobId parameter. If the specified job cannot be located, the promise callback parameter will be set to null.

Arguments

  jobId {String} A string identifying the ID of the to look up.
  returns {Promise} A promise that resolves with the job instance when the job
  has been retrieved to the queue, or null otherwise.

---

#### Queue##clean(options)

Tells the queue remove all jobs created outside of a grace period. You can clean the jobs with the following states: completed, waiting, active, delayed, and failed.

Example

//cleans all jobs that completed over 5 seconds ago.
queue.clean(5000);
//clean all jobs that failed over 10 seconds ago.
queue.clean(10000, 'failed');
queue.on('cleaned', function (job, type) {
  console.log('Cleaned %s %s jobs', job.length, type);
});

Arguments

  grace {int} Grace period in milliseconds.
  type {string} type of job to clean. Values are completed, waiting, active,
  delayed, and failed. Defaults to completed.
  returns {Promise} A promise that resolves with an array of removed jobs.

Events

The cleaner emits the cleaned event anytime the queue is cleaned.

  queue.on('cleaned', function (jobs, type) {}); 

  jobs {Array} An array of jobs that have been cleaned.
  type {String} The type of job cleaned. Options are completed, waiting, active,
  delayed, or failed.

---

###PriorityQueue(queueName, redisPort, redisHost, [redisOpts])

This is the Queue constructor of priority queue. It works same a normal queue, with same function and parameters. The only difference is that the Queue#add() allow an options opts.priority that could take ["low", "normal", "medium", "hight", "critical"]. If no options provider, "normal" will be taken.

The priority queue will process more often highter priority jobs than lower.

  var PriorityQueue = require("bull/lib/priority-queue");

  var queue = new PriorityQueue("myPriorityQueues");

  queue.add({todo: "Improve feature"}, {priority: "normal"});
  queue.add({todo: "Read 9gags"}, {priority: "low"});
  queue.add({todo: "Fix my test unit"}, {priority: "critical"});

  queue.process(function(job, done) {
    console.log("I have to: " + job.data.todo);
    done();
  });

Warning: Priority queue use 5 times more redis connections than a normal queue.

### Job

A job includes all data needed to perform its execution, as well as the progress method needed to update its progress.

The most important property for the user is Job##data that includes the object that was passed to Queue##add, and that is normally used to perform the job.

---

#### Job##remove()

Removes a Job from the queue from all the lists where it may be included.

Arguments

  returns {Promise} A promise that resolves when the job is removed.

---

#### Job##retry()

Rerun a Job that has failed.

Arguments

  returns {Promise} A promise that resolves when the job is scheduled for retry.

---

##License

(The MIT License)

Copyright (c) 2013 Manuel Astudillo [email protected]

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.