Active Job

Introduction

Active Job is a framework help developers writing codes and run them on the background automatically under different scenarios. Jobs can vary from schedule newsletter, follow-up emails to database housekeeping. It’s a interface that adapts different queueing backends like Backburner[1], Delayed Job[2], Qu[3] and so on. <ref>http://guides.rubyonrails.org/active_job_basics.html</ref> Overall, Active Job is a interface which you can work with common queues.

Active Job adapters<ref>http://edgeapi.rubyonrails.org/classes/ActiveJob/QueueAdapters.html</ref>

• Backburner[4]
• Delayed Job[5]
• Qu[6]
• Que[7]
• queue_classic[8]
• Resque 1.x[9]
• Sidekiq[10]
• Sneakers[11]
• Sucker Punch[12]
• Active Job Async Job
• Active Job Inline[13]

How to use <ref>http://guides.rubyonrails.org/active_job_basics.html</ref>

We will introduce how to creating a job and and how to add the job into a queue. <ref name= "Active-Job-Basics">Rails Guides “Active Job Basics” 2014</ref>

Download

With RubyGems you can install the Active Job into your computer:

$ gem install activejob

Souce code of Active Job available on GitHub, as part of Rails.<ref> GitHub “Active Job -- Make work happen later” 2015 </ref>

Create a Job

In Active Job, a process which is inserted in a queue and waiting for carry out is called “Job”. It’s possible to generate a Job using the Generator provided by Rails. You can create a job in app/jobs, with the name “update_wiki”, by doing the following.

$ bin/rails generate job update_wiki
  invoke  test_unit
  create  test/jobs/update_wiki_job_test.rb
  create  app/jobs/update_wiki_job.rb

Active Job provides the ability to run your Job on a specific queue by create a job as following:

$ bin/rails generate job update_wiki --queue urgent

Files inside of app/jobs can be created manually, instead of using a generator. In Rails 4.2 an ActiveJob class inherits from ActiveJob::Base. In Rails 5.0, it has changed to now inherit from ApplicationJob. When upgrading from Rails 4.2 to Rails 5.0, an application_job.rb file is needed to be created in app/jobs/ and add the following content:<ref> Rails Guides “A Guide for Upgrading Ruby on Rails” 2015 </ref>

class ApplicationJob < ActiveJob::Base
end

In Rails 4.2 a Job class looks like:

class UpdateWikiJob < ActiveJob::Base
  queue_as :default
 
  def perform(*wiki)
   # Do something later
  wiki.update_contents
  end
end

There is a perform method to be called when the job was first enqueued.

Adding a Job to the queue

If you wish your Job be processed as soon as the queuing system is free, you can enqueue a Job like:

UpdateWikiJob.perform_later wiki

Or you can add a Job be performed tomorrow at noon:

UpdateWikiJob.set(wait_until: Date.tomorrow.noon).perform_later(wiki)

If you want your Job be performed a week from now, most of the queueing backends ( Sidekiq , Delayed Job, etc. ) allow you to set a delay time.

UpdateWikiJob.set(wait: 1.week).perform_later(wiki)

Execution of Job

Active Job provides adapters for multiple queueing backends (Sidekiq, Resque, Delayed Job and others).<ref name= "Active-Job-Basics">Rails Guides “Active Job Basics” 2014</ref> Without setting any adapter, the job would be performed immediately.
Queueing backend can be set at: /config/application.rb, in this example we use the Sidekiq.

module YourApp
  class Application < Rails::Application
    # Be sure to have the adapter's gem in your Gemfile and follow
    # the adapter's specific installation and deployment instructions.
    config.active_job.queue_adapter = :sidekiq
  end
end

Play with Queues

Active Job allows to schedule the job to be processed on a specific queue, this became helpful as common adapters support multiple queues.

class UpdateWikiJob < ActiveJob::Base
  queue_as :low_priority
  #....
end

Queue name can be prefixed for all jobs using config.active_job.queue_name_prefixin application.rb:

# config/application.rb
module YourApp
  class Application < Rails::Application
    config.active_job.queue_name_prefix = Rails.env
  end
end
 
# app/jobs/update_wiki_job.rb
class UpdateWikiJob < ActiveJob::Base
  queue_as :low_priority
  #....
end
 
# Now your job will run on queue production_low_priority on your
# production environment and on staging_low_priority on your staging
# environment

You can control a job to run on a queue you like, by passing a :queue option to #set :

MyJob.set(queue: :another_queue).perform_later(record)

All the code snippets are referred from the source<ref name= "Active-Job-Basics">Rails Guides “Active Job Basics” 2014</ref>

References

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