Active Job is a framework for declaring jobs and making them run on a variety of queueing backends. These jobs can be everything from regularly scheduled clean-ups, to billing charges, to mailings. Anything that can be chopped up into small units of work and run in parallel, really.
2 The Purpose of the Active Job
The main point is to ensure that all Rails apps will have a job infrastructure in place, even if it's in the form of an "immediate runner". We can then have framework features and other gems build on top of that, without having to worry about API differences between various job runners such as Delayed Job and Resque. Picking your queuing backend becomes more of an operational concern, then. And you'll be able to switch between them without having to rewrite your jobs.
3 Creating a Job
This section will provide a step-by-step guide to creating a job and enqueuing it.
3.1 Create the Job
Active Job provides a Rails generator to create jobs. The following will create a
$ bin/rails generate job guests_cleanup create app/jobs/guests_cleanup_job.rb
You can also create a job that will run on a specific queue:
$ bin/rails generate job guests_cleanup --queue urgent create app/jobs/guests_cleanup_job.rb
As you can see, you can generate jobs just like you use other generators with Rails.
If you don't want to use a generator, you could create your own file inside of
app/jobs, just make sure that it inherits from
Here's what a job looks like:
class GuestsCleanupJob < ActiveJob::Base queue_as :default def perform(*args) # Do something later end end
3.2 Enqueue the Job
Enqueue a job like so:
MyJob.perform_later record # Enqueue a job to be performed as soon the queueing system is free.
MyJob.set(wait_until: Date.tomorrow.noon).perform_later(record) # Enqueue a job to be performed tomorrow at noon.
MyJob.set(wait: 1.week).perform_later(record) # Enqueue a job to be performed 1 week from now.
4 Job Execution
If no adapter is set, the job is immediately executed.
Active Job has built-in adapters for multiple queueing backends (Sidekiq, Resque, Delayed Job and others). To get an up-to-date list of the adapters see the API Documentation for ActiveJob::QueueAdapters.
4.2 Changing the Backend
You can easily change your queueing backend:
# be sure to have the adapter gem in your Gemfile and follow the adapter specific # installation and deployment instructions Rails.application.config.active_job.queue_adapter = :sidekiq
Most of the adapters support multiple queues. With Active Job you can schedule the job to run on a specific queue:
class GuestsCleanupJob < ActiveJob::Base queue_as :low_priority #.... end
You can prefix the queue name for all your jobs using
# config/application.rb module YourApp class Application < Rails::Application config.active_job.queue_name_prefix = Rails.env end end # app/jobs/guests_cleanup.rb class GuestsCleanupJob < ActiveJob::Base queue_as :low_priority #.... end # Now your job will run on queue production_low_priority on your # production environment and on beta_low_priority on your beta # environment
If you want more control on what queue a job will be run you can pass a :queue option to #set:
To control the queue from the job level you can pass a block to queue_as. The block will be executed in the job context (so you can access self.arguments) and you must return the queue name:
class ProcessVideoJob < ActiveJob::Base queue_as do video = self.arguments.first if video.owner.premium? :premium_videojobs else :videojobs end end def perform(video) # do process video end end ProcessVideoJob.perform_later(Video.last)
Make sure your queueing backend "listens" on your queue name. For some backends you need to specify the queues to listen to.
Active Job provides hooks during the lifecycle of a job. Callbacks allow you to trigger logic during the lifecycle of a job.
6.1 Available callbacks
class GuestsCleanupJob < ActiveJob::Base queue_as :default before_enqueue do |job| # do something with the job instance end around_perform do |job, block| # do something before perform block.call # do something after perform end def perform # Do something later end end
One of the most common jobs in a modern web application is sending emails outside of the request-response cycle, so the user doesn't have to wait on it. Active Job is integrated with Action Mailer so you can easily send emails asynchronously:
# If you want to send the email now use #deliver_now UserMailer.welcome(@user).deliver_now # If you want to send the email through Active Job use #deliver_later UserMailer.welcome(@user).deliver_later
Active Job supports GlobalID for parameters. This makes it possible to pass live Active Record objects to your job instead of class/id pairs, which you then have to manually deserialize. Before, jobs would look like this:
class TrashableCleanupJob def perform(trashable_class, trashable_id, depth) trashable = trashable_class.constantize.find(trashable_id) trashable.cleanup(depth) end end
Now you can simply do:
class TrashableCleanupJob def perform(trashable, depth) trashable.cleanup(depth) end end
This works with any class that mixes in
by default has been mixed into Active Model classes.
Active Job provides a way to catch exceptions raised during the execution of the job:
class GuestsCleanupJob < ActiveJob::Base queue_as :default rescue_from(ActiveRecord::RecordNotFound) do |exception| # do something with the exception end def perform # Do something later end end
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