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diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md index 29d0c32b09..c65d1e6de5 100644 --- a/guides/source/active_job_basics.md +++ b/guides/source/active_job_basics.md @@ -4,7 +4,7 @@ Active Job Basics ================= This guide provides you with all you need to get started in creating, -enqueueing and executing background jobs. +enqueuing and executing background jobs. After reading this guide, you will know: @@ -20,7 +20,7 @@ Introduction ------------ 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 +of queuing 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. @@ -28,11 +28,15 @@ into small units of work and run in parallel, really. The Purpose of 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. +in place. 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. + +NOTE: Rails by default comes with an asynchronous queuing implementation that +runs jobs with an in-process thread pool. Jobs will run asynchronously, but any +jobs in the queue will be dropped upon restart. Creating a Job @@ -59,57 +63,69 @@ $ bin/rails generate job guests_cleanup --queue urgent ``` 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 `ActiveJob::Base`. +`app/jobs`, just make sure that it inherits from `ApplicationJob`. Here's what a job looks like: ```ruby -class GuestsCleanupJob < ActiveJob::Base +class GuestsCleanupJob < ApplicationJob queue_as :default - def perform(*args) + def perform(*guests) # Do something later end end ``` +Note that you can define `perform` with as many arguments as you want. + ### Enqueue the Job Enqueue a job like so: ```ruby -# Enqueue a job to be performed as soon the queueing system is +# Enqueue a job to be performed as soon as the queuing system is # free. -MyJob.perform_later record +GuestsCleanupJob.perform_later guest ``` ```ruby # Enqueue a job to be performed tomorrow at noon. -MyJob.set(wait_until: Date.tomorrow.noon).perform_later(record) +GuestsCleanupJob.set(wait_until: Date.tomorrow.noon).perform_later(guest) ``` ```ruby # Enqueue a job to be performed 1 week from now. -MyJob.set(wait: 1.week).perform_later(record) +GuestsCleanupJob.set(wait: 1.week).perform_later(guest) ``` -That's it! +```ruby +# `perform_now` and `perform_later` will call `perform` under the hood so +# you can pass as many arguments as defined in the latter. +GuestsCleanupJob.perform_later(guest1, guest2, filter: 'some_filter') +``` +That's it! Job Execution ------------- -If no adapter is set, the job is immediately executed. +For enqueuing and executing jobs in production you need to set up a queuing backend, +that is to say you need to decide for a 3rd-party queuing library that Rails should use. +Rails itself only provides an in-process queuing system, which only keeps the jobs in RAM. +If the process crashes or the machine is reset, then all outstanding jobs are lost with the +default async back-end. This may be fine for smaller apps or non-critical jobs, but most +production apps will need to pick a persistent backend. ### Backends -Active Job has built-in adapters for multiple queueing backends (Sidekiq, +Active Job has built-in adapters for multiple queuing backends (Sidekiq, Resque, Delayed Job and others). To get an up-to-date list of the adapters see the API Documentation for [ActiveJob::QueueAdapters](http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters.html). ### Setting the Backend -You can easily set your queueing backend: +You can easily set your queuing backend: ```ruby # config/application.rb @@ -123,6 +139,31 @@ module YourApp end ``` +You can also configure your backend on a per job basis. + +```ruby +class GuestsCleanupJob < ApplicationJob + self.queue_adapter = :resque + #.... +end + +# Now your job will use `resque` as it's backend queue adapter overriding what +# was configured in `config.active_job.queue_adapter`. +``` + +### Starting the Backend + +Since jobs run in parallel to your Rails application, most queuing libraries +require that you start a library-specific queuing service (in addition to +starting your Rails app) for the job processing to work. Refer to library +documentation for instructions on starting your queue backend. + +Here is a noncomprehensive list of documentation: + +- [Sidekiq](https://github.com/mperham/sidekiq/wiki/Active-Job) +- [Resque](https://github.com/resque/resque/wiki/ActiveJob) +- [Sucker Punch](https://github.com/brandonhilkert/sucker_punch#active-job) +- [Queue Classic](https://github.com/QueueClassic/queue_classic#active-job) Queues ------ @@ -131,7 +172,7 @@ Most of the adapters support multiple queues. With Active Job you can schedule the job to run on a specific queue: ```ruby -class GuestsCleanupJob < ActiveJob::Base +class GuestsCleanupJob < ApplicationJob queue_as :low_priority #.... end @@ -148,8 +189,8 @@ module YourApp end end -# app/jobs/guests_cleanup.rb -class GuestsCleanupJob < ActiveJob::Base +# app/jobs/guests_cleanup_job.rb +class GuestsCleanupJob < ApplicationJob queue_as :low_priority #.... end @@ -171,8 +212,8 @@ module YourApp end end -# app/jobs/guests_cleanup.rb -class GuestsCleanupJob < ActiveJob::Base +# app/jobs/guests_cleanup_job.rb +class GuestsCleanupJob < ApplicationJob queue_as :low_priority #.... end @@ -194,7 +235,7 @@ block will be executed in the job context (so you can access `self.arguments`) and you must return the queue name: ```ruby -class ProcessVideoJob < ActiveJob::Base +class ProcessVideoJob < ApplicationJob queue_as do video = self.arguments.first if video.owner.premium? @@ -212,7 +253,7 @@ end ProcessVideoJob.perform_later(Video.last) ``` -NOTE: Make sure your queueing backend "listens" on your queue name. For some +NOTE: Make sure your queuing backend "listens" on your queue name. For some backends you need to specify the queues to listen to. @@ -234,7 +275,7 @@ trigger logic during the life cycle of a job. ### Usage ```ruby -class GuestsCleanupJob < ActiveJob::Base +class GuestsCleanupJob < ApplicationJob queue_as :default before_enqueue do |job| @@ -270,6 +311,19 @@ UserMailer.welcome(@user).deliver_later ``` +Internationalization +-------------------- + +Each job uses the `I18n.locale` set when the job was created. Useful if you send +emails asynchronously: + +```ruby +I18n.locale = :eo + +UserMailer.welcome(@user).deliver_later # Email will be localized to Esperanto. +``` + + GlobalID -------- @@ -278,7 +332,7 @@ Active Record objects to your job instead of class/id pairs, which you then have to manually deserialize. Before, jobs would look like this: ```ruby -class TrashableCleanupJob < ActiveJob::Base +class TrashableCleanupJob < ApplicationJob def perform(trashable_class, trashable_id, depth) trashable = trashable_class.constantize.find(trashable_id) trashable.cleanup(depth) @@ -289,7 +343,7 @@ end Now you can simply do: ```ruby -class TrashableCleanupJob < ActiveJob::Base +class TrashableCleanupJob < ApplicationJob def perform(trashable, depth) trashable.cleanup(depth) end @@ -307,7 +361,7 @@ Active Job provides a way to catch exceptions raised during the execution of the job: ```ruby -class GuestsCleanupJob < ActiveJob::Base +class GuestsCleanupJob < ApplicationJob queue_as :default rescue_from(ActiveRecord::RecordNotFound) do |exception| @@ -320,6 +374,13 @@ class GuestsCleanupJob < ActiveJob::Base end ``` +### Deserialization + +GlobalID allows serializing full Active Record objects passed to `#perform`. + +If a passed record is deleted after the job is enqueued but before the `#perform` +method is called Active Job will raise an `ActiveJob::DeserializationError` +exception. Job Testing -------------- |