Kue

Kue is a priority job queue backed by redis, built for node.js.

Installation

$ npm install kue

Features

delayed jobs
job event and progress pubsub
rich integrated UI
infinite scrolling
UI progress indication
job specific logging
powered by Redis
optional retries
full-text search capabilities
RESTful JSON API

Creating Jobs

First create a job Queue with kue.createQueue():

var kue = require('kue')
  , jobs = kue.createQueue();

Calling jobs.create() with the type of job ("email"), and arbitrary job data will return a Job, which can then be save()ed, adding it to redis, with a default priority level of "normal". The save() method optionally accepts a callback, responding with an error if something goes wrong. The title key is special-cased, and will display in the job listings within the UI, making it easier to find a specific job.

jobs.create('email', {
    title: 'welcome email for tj'
  , to: 'tj@learnboost.com'
  , template: 'welcome-email'
}).save();

Job Priority

To specify the priority of a job, simply invoke the priority() method with a number, or priority name, which is mapped to a number.

jobs.create('email', {
    title: 'welcome email for tj'
  , to: 'tj@learnboost.com'
  , template: 'welcome-email'
}).priority('high').save();

The default priority map is as follows:

{
    low: 10
  , normal: 0
  , medium: -5
  , high: -10
  , critical: -15
};

Failure Attempts

By default jobs only have one attempt, that is when they fail, they are marked as a failure, and remain that way until you intervene. However, Kue allows you to specify this, which is important for jobs such as transferring an email, which upon failure, may usually retry without issue. To do this invoke the .attempts() method with a number.

jobs.create('email', {
    title: 'welcome email for tj'
  , to: 'tj@learnboost.com'
  , template: 'welcome-email'
}).priority('high').attempts(5).save();

Job Logs

Job-specific logs enable you to expose information to the UI at any point in the job's life-time. To do so simply invoke job.log(), which accepts a message string as well as variable-arguments for sprintf-like support:

job.log('$%d sent to %s', amount, user.name);

Job Progress

Job progress is extremely useful for long-running jobs such as video conversion. To update the job's progress simply invoke job.progress(completed, total):

job.progress(frames, totalFrames);

Job Events

Job-specific events are fired on the Job instances via Redis pubsub. The following events are currently supported:

- `failed` the job has failed
- `complete` the job has completed
- `promotion` the job (when delayed) is now queued
- `progress` the job's progress ranging from 0-100

For example this may look something like the following:

var job = jobs.create('video conversion', {
    title: 'converting loki\'s to avi'
  , user: 1
  , frames: 200
});

job.on('complete', function(){
  console.log("Job complete");
}).on('failed', function(){
  console.log("Job failed");
}).on('progress', function(progress){
  process.stdout.write('\r  job #' + job.id + ' ' + progress + '% complete');
});

Queue Events

Queue-level events are currently provide access to the job-level events previously mentioned, however scoped to the Queue instance to to apply logic at a "global" level. An example of this is removing completed jobs:

jobs.on('job complete', function(id){
  Job.get(id, function(err, job){
    if (err) return;
    job.remove(function(err){
      if (err) throw err;
      console.log('removed completed job #%d', job.id);
    });
  });
});

The events available are the same as mentioned in "Job Events", however prefixed with "job ".

Delayed Jobs

Delayed jobs may be scheduled to be queued for an arbitrary distance in time by invoking the .delay(ms) method, passing the number of milliseconds relative to now. This automatically flags the Job as "delayed".

var email = jobs.create('email', {
    title: 'Account renewal required'
  , to: 'tj@learnboost.com'
  , template: 'renewal-email'
}).delay(minute)
  .priority('high')
  .save();

When using delayed jobs, we must also check the delayed jobs with a timer, promoting them if the scheduled delay has been exceeded. This setInterval is defined within Queue#promote(ms), defaulting to a check every 5 seconds.

jobs.promote();

Processing Jobs

Processing jobs is simple with Kue. First create a Queue instance much like we do for creating jobs, providing us access to redis etc, then invoke jobs.process() with the associated type.

In the following example we pass the callback done to email, if this function responds with an error it will be displayed in the UI and the job will be marked as a failure.

var kue = require('kue')
 , jobs = kue.createQueue();

jobs.process('email', function(job, done){
  email(job.data.to, done);
});

Processing Concurrency

By default a call to jobs.process() will only accept one job at a time for processing. For small tasks like sending emails this is not ideal, so we may specify the maximum active jobs for this type by passing a number:

jobs.process('email', 20, function(job, done){
  // ...
});

Updating Progress

For a "real" example, let's say we need to compile a PDF from numerous slides with node-canvas. Our job may consist of the following data, note that in general you should not store large data in the job it-self, it's better to store references like ids, pulling them in while processing.

jobs.create('slideshow pdf', {
    title: user.name + "'s slideshow"
  , slides: [...] // keys to data stored in redis, mongodb, or some other store
});

We can access this same arbitrary data within a separate process while processing, via the job.data property. In the example we render each slide one-by-one, updating the job's log and process. When an error occurs we invoke done(err) to tell Kue something happened, otherwise we invoke done() only when the job is complete.

jobs.process('slideshow pdf', 5, function(job, done){
  var slides = job.data.slides
    , len = slides.length;

  function next(i) {
    var slide = slides[i]; // pretend we did a query on this slide id ;)
    job.log('rendering %dx%d slide', slide.width, slide.height);
    renderSlide(slide, function(err){
      if (err) return done(err);
      job.progress(i, len);
      if (i == len) done()
      else next(i + 1);
    });
  }

  next(0);
});

Redis Connection Settings

By default, Kue will connect to Redis using the client default settings (port defaults to 6389, host defaults to 127.0.0.1). Redis client connection settings can be set by overriding the kue.redis.createClient function.

For example, to create a Redis client that connects to 192.168.1.2 on port 1234 that requires authentication, use the following:

var kue = require('kue')
  , redis = require('redis');

kue.redis.createClient = function() {
  var client = redis.createClient(1234, '192.168.1.2');
  client.auth('password');
  return client;
};

Redis connection settings must be set before calling kue.createQueue() or accessing kue.app.

User-Interface

The UI is a small Express application, to fire it up simply run the following, altering the port etc as desired.

var kue = require('kue');
kue.app.listen(3000);

The title defaults to "Kue", to alter this invoke:

kue.app.set('title', 'My Application');

JSON API

Along with the UI Kue also exposes a JSON API, which is utilized by the UI.

GET /job/search?q=

Query jobs, for example "GET /job/search?q=avi video":

["5", "7", "10"]

GET /stats

Currently responds with state counts, and worker activity time in milliseconds:

{"inactiveCount":4,"completeCount":69,"activeCount":2,"failedCount":0,"workTime":20892}

GET /job/:id

Get a job by :id:

{"id":"3","type":"email","data":{"title":"welcome email for tj","to":"tj@learnboost.com","template":"welcome-email"},"priority":-10,"progress":"100","state":"complete","attempts":null,"created_at":"1309973155248","updated_at":"1309973155248","duration":"15002"}

GET /job/:id/log

Get job :id's log:

['foo', 'bar', 'baz']

GET /jobs/:from..:to/:order?

Get jobs with the specified range :from to :to, for example "/jobs/0..2", where :order may be "asc" or "desc":

[{"id":"12","type":"email","data":{"title":"welcome email for tj","to":"tj@learnboost.com","template":"welcome-email"},"priority":-10,"progress":0,"state":"active","attempts":null,"created_at":"1309973299293","updated_at":"1309973299293"},{"id":"130","type":"email","data":{"title":"welcome email for tj","to":"tj@learnboost.com","template":"welcome-email"},"priority":-10,"progress":0,"state":"active","attempts":null,"created_at":"1309975157291","updated_at":"1309975157291"}]

GET /jobs/:state/:from..:to/:order?

Same as above, restricting by :state which is one of:

- active
- inactive
- failed
- complete

GET /jobs/:type/:state/:from..:to/:order?

Same as above, however restricted to :type and :state.

DELETE /job/:id

Delete job :id:

$ curl -X DELETE http://local:3000/job/2
{"message":"job 2 removed"}

Parallel Processing With Cluster

The example below shows how you may use Cluster to spread the job processing load across CPUs. By default cluster will create one worker per CPU, however you can specify this number via .set('workers', N).

When cluster .isMaster the file is being executed in context of the master process, in which case you may perform tasks that you only want once, such as starting the web app bundled with Kue. The logic in the else block is executed per worker.

var kue = require('kue')
  , cluster = require('cluster')
  , jobs = kue.createQueue();

cluster = cluster()
  .set('workers', 8)
  .use(cluster.debug())
  .start();

if (cluster.isMaster) {
  kue.app.listen(3000);
} else {
  jobs.process('email', function(job, done){
    var pending = 5
      , total = pending;

    setInterval(function(){
      job.log('sending!');
      job.progress(total - pending, total);
      --pending || done();
    }, 1000);
  });
}

running this example you'll see the following output:

$ node kue-example
info - master started
info - worker 0 spawned
info - worker 1 spawned
info - worker 2 spawned
info - listening for connections
info - worker 2 connected
info - worker 1 connected
info - worker 0 connected

now when you visit Kue's UI in the browser you'll see that jobs are being processed roughly 8 times faster! (if you have 8 cores).

Securing Kue

Through the use of app mounting you may customize the web application, enabling TLS, or adding additional middleware like Connect's basicAuth().

var app = express.createServer({ ... tls options ... });
app.use(express.basicAuth('foo', 'bar'));
app.use(kue.app);
app.listen(3000);

Screencasts

Introduction to Kue
API walkthrough to Kue

License

(The MIT License)

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.

austein/kue

Kue