Active Job Basics

1. What is Active Job?

Active Job is a framework in Rails designed for declaring background jobs and executing them on a queuing backend. It provides a standardized interface for tasks like sending emails, processing data, or handling regular maintenance activities, such as clean-ups and billing charges. By offloading these tasks from the main application thread to a queuing backend like the default Solid Queue, Active Job ensures that time-consuming operations do not block the request-response cycle. This can improve the performance and responsiveness of the application, allowing it to handle tasks in parallel.

2. Create and Enqueue Jobs

This section will provide a step-by-step guide to create a job and enqueue it.

2.1. Create the Job

Active Job provides a Rails generator to create jobs. The following will create a job in app/jobs (with an attached test case under test/jobs):

$ bin/rails generate job guests_cleanup
invoke  test_unit
create    test/jobs/guests_cleanup_job_test.rb
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

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 ApplicationJob.

Here's what a job looks like:

class GuestsCleanupJob < ApplicationJob
  queue_as :default

  def perform(*guests)
    # Do something later
  end
end

Note that you can define perform with as many arguments as you want.

If you already have an abstract class and its name differs from ApplicationJob, you can pass the --parent option to indicate you want a different abstract class:

$ bin/rails generate job process_payment --parent=payment_job

class ProcessPaymentJob < PaymentJob
  queue_as :default

  def perform(*args)
    # Do something later
  end
end

2.2. Enqueue the Job

Enqueue a job using perform_later and, optionally, set. Like so:

# Enqueue a job to be performed as soon as the queuing system is
# free.
GuestsCleanupJob.perform_later guest

# Enqueue a job to be performed tomorrow at noon.
GuestsCleanupJob.set(wait_until: Date.tomorrow.noon).perform_later(guest)

# Enqueue a job to be performed 1 week from now.
GuestsCleanupJob.set(wait: 1.week).perform_later(guest)

# `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!

2.3. Enqueue Jobs in Bulk

You can enqueue multiple jobs at once using perform_all_later. For more details see Bulk Enqueuing.

3. Default Backend: Solid Queue

Solid Queue, which is enabled by default from Rails version 8.0 and onward, is a database-backed queuing system for Active Job, allowing you to queue large amounts of data without requiring additional dependencies such as Redis.

Besides regular job enqueuing and processing, Solid Queue supports delayed jobs, concurrency controls, numeric priorities per job, priorities by queue order, and more.

3.1. Set Up

3.1.1. Development

In development, Rails provides an asynchronous in-process queuing system, which keeps the jobs in RAM. If the process crashes or the machine is reset, then all outstanding jobs are lost with the default async backend. This can be fine for smaller apps or non-critical jobs in development.

However, if you use Solid Queue instead, you can configure it in the same way as in the production environment:

# config/environments/development.rb
config.active_job.queue_adapter = :solid_queue
config.solid_queue.connects_to = { database: { writing: :queue } }

which sets the :solid_queue adapter as the default for Active Job in the production environment, and connects to the queue database for writing.

Thereafter, you'd add queue to the development database configuration:

# config/database.yml
development:
  primary:
    <<: *default
    database: storage/development.sqlite3
  queue:
    <<: *default
    database: storage/development_queue.sqlite3
    migrations_paths: db/queue_migrate

You can run the migrations for the queue database to ensure all the tables in queue database are created:

$ bin/rails db:migrate:queue

Finally, to start the queue and start processing jobs you can run:

bin/jobs start

3.1.2. Production

Solid Queue is already configured for the production environment. If you open config/environments/production.rb, you will see the following:

# config/environments/production.rb
# Replace the default in-process and non-durable queuing backend for Active Job.
config.active_job.queue_adapter = :solid_queue
config.solid_queue.connects_to = { database: { writing: :queue } }

Additionally, the database connection for the queue database is configured in config/database.yml:

# config/database.yml
# Store production database in the storage/ directory, which by default
# is mounted as a persistent Docker volume in config/deploy.yml.
production:
  primary:
    <<: *default
    database: storage/production.sqlite3
  queue:
    <<: *default
    database: storage/production_queue.sqlite3
    migrations_paths: db/queue_migrate

3.2. Configuration

The configuration options for Solid Queue are defined in config/queue.yml. Here is an example of the default configuration:

default: &default
  dispatchers:
    - polling_interval: 1
      batch_size: 500
  workers:
    - queues: "*"
      threads: 3
      processes: <%= ENV.fetch("JOB_CONCURRENCY", 1) %>
      polling_interval: 0.1

In order to understand the configuration options for Solid Queue, you must understand the different types of roles:

• Dispatchers: They select jobs scheduled to run for the future. When it's time for these jobs to run, dispatchers move them from the solid_queue_scheduled_executions table to the solid_queue_ready_executions table so workers can pick them up. They also manage concurrency-related maintenance.
• Workers: They pick up jobs that are ready to run. These jobs are taken from the solid_queue_ready_executions table.
• Scheduler: This takes care of recurring tasks, adding jobs to the queue when they're due.
• Supervisor: It oversees the whole system, managing workers and dispatchers. It starts and stops them as needed, monitors their health, and ensures everything runs smoothly.

Everything is optional in the config/queue.yml. If no configuration is provided, Solid Queue will run with one dispatcher and one worker with default settings. Below are some of the configuration options you can set in config/queue.yml:

You can read more about these configuration options in the Solid Queue documentation. There are also additional configuration options that can be set in config/<environment>.rb to further configure Solid Queue in your Rails Application.

3.3. Queue Order

As per the configuration options in the Configuration section, the queues configuration option will list the queues that workers will pick jobs from. In a list of queues, the order matters. Workers will pick jobs from the first queue in the list - once there are no more jobs in the first queue, only then will it move onto the second, and so on.

# config/queue.yml
production:
  workers:
    - queues:[active_storage*, mailers]
      threads: 3
      polling_interval: 5

In the above example, workers will fetch jobs from queues starting with "active_storage", like the active_storage_analyse queue and active_storage_transform queue. Only when no jobs remain in the active_storage-prefixed queues will workers move on to the mailers queue.

Active Job supports positive integer priorities when enqueuing jobs (see Priority section). Within a single queue, jobs are picked based on their priority (with lower integers being higher priority). However, when you have multiple queues, the order of the queues themselves takes priority.

For example, if you have two queues, production and background, jobs in the production queue will always be processed first, even if some jobs in the background queue have a higher priority.

3.4. Threads, Processes, and Signals

In Solid Queue, parallelism is achieved through threads (configurable via the threads parameter), processes (via the processes parameter), or horizontal scaling. The supervisor manages processes and responds to the following signals:

• TERM, INT: Starts graceful termination, sending a TERM signal and waiting up to SolidQueue.shutdown_timeout. If not finished, a QUIT signal forces processes to exit.
• QUIT: Forces immediate termination of processes.

If a worker is killed unexpectedly (e.g., with a KILL signal), in-flight jobs are marked as failed, and errors like SolidQueue::Processes::ProcessExitError or SolidQueue::Processes::ProcessPrunedError are raised. Heartbeat settings help manage and detect expired processes. Read more about Threads, Processes and Signals in the Solid Queue documentation.

3.5. Errors When Enqueuing

Solid Queue raises a SolidQueue::Job::EnqueueError when Active Record errors occur during job enqueuing. This is different from the ActiveJob::EnqueueError raised by Active Job, which handles the error and makes perform_later return false. This makes error handling trickier for jobs enqueued by Rails or third-party gems like Turbo::Streams::BroadcastJob.

For recurring tasks, any errors encountered while enqueuing are logged, but they won’t be raised. Read more about Errors When Enqueuing in the Solid Queue documentation.

3.6. Concurrency Controls

Solid Queue extends Active Job with concurrency controls, allowing you to limit how many jobs of a certain type or with specific arguments can run at the same time. If a job exceeds the limit, it will be blocked until another job finishes or the duration expires. For example:

class MyJob < ApplicationJob
  limits_concurrency to: 2, key: ->(contact) { contact.account }, duration: 5.minutes

  def perform(contact)
    # perform job logic
  end
end

In this example, only two MyJob instances for the same account will run concurrently. After that, other jobs will be blocked until one completes.

The group parameter can be used to control concurrency across different job types. For instance, two different job classes that use the same group will have their concurrency limited together:

class Box::MovePostingsByContactToDesignatedBoxJob < ApplicationJob
  limits_concurrency key: ->(contact) { contact }, duration: 15.minutes, group: "ContactActions"
end

class Bundle::RebundlePostingsJob < ApplicationJob
  limits_concurrency key: ->(bundle) { bundle.contact }, duration: 15.minutes, group: "ContactActions"
end

This ensures that only one job for a given contact can run at a time, regardless of the job class.

Read more about Concurrency Controls in the Solid Queue documentation.

3.7. Error Reporting on Jobs

If your error tracking service doesn’t automatically report job errors, you can manually hook into Active Job to report them. For example, you can add a rescue_from block in ApplicationJob:

class ApplicationJob < ActiveJob::Base
  rescue_from(Exception) do |exception|
    Rails.error.report(exception)
    raise exception
  end
end

If you use ActionMailer, you’ll need to handle errors for MailDeliveryJob separately:

class ApplicationMailer < ActionMailer::Base
  ActionMailer::MailDeliveryJob.rescue_from(Exception) do |exception|
    Rails.error.report(exception)
    raise exception
  end
end

3.8. Transactional Integrity on Jobs

By default, Solid Queue uses a separate database from your main application. This avoids issues with transactional integrity, which ensures that jobs are only enqueued if the transaction commits.

However, if you use Solid Queue in the same database as your app, you can enable transactional integrity with Active Job’s enqueue_after_transaction_commit option which can be enabled for individual jobs or all jobs through ApplicationJob:

class ApplicationJob < ActiveJob::Base
  self.enqueue_after_transaction_commit = true
end

You can also configure Solid Queue to use the same database as your app while avoiding transactional integrity issues by setting up a separate database connection for Solid Queue jobs. Read more about Transactional Integrity in the Solid Queue documentation

3.9. Recurring Tasks

Solid Queue supports recurring tasks, similar to cron jobs. These tasks are defined in a configuration file (by default, config/recurring.yml) and can be scheduled at specific times. Here's an example of a task configuration:

production:
  a_periodic_job:
    class: MyJob
    args: [42, { status: "custom_status" }]
    schedule: every second
  a_cleanup_task:
    command: "DeletedStuff.clear_all"
    schedule: every day at 9am

Each task specifies a class or command and a schedule (parsed using Fugit). You can also pass arguments to jobs, such as in the example for MyJob where args are passed. This can be passed as a single argument, a hash, or an array of arguments that can also include kwargs as the last element in the array. This allows jobs to run periodically or at specified times.

Read more about Recurring Tasks in the Solid Queue documentation.

3.10. Job Tracking and Management

A tool like mission_control-jobs can help centralize the monitoring and management of failed jobs. It provides insights into job statuses, failure reasons, and retry behaviors, enabling you to track and resolve issues more effectively.

For instance, if a job fails to process a large file due to a timeout, mission_control-jobs allows you to inspect the failure, review the job’s arguments and execution history, and decide whether to retry, requeue, or discard it.

4. Queues

With Active Job you can schedule the job to run on a specific queue using queue_as:

class GuestsCleanupJob < ApplicationJob
  queue_as :low_priority
  # ...
end

You can prefix the queue name for all your jobs using config.active_job.queue_name_prefix in application.rb:

# config/application.rb
module YourApp
  class Application < Rails::Application
    config.active_job.queue_name_prefix = Rails.env
  end
end

# app/jobs/guests_cleanup_job.rb
class GuestsCleanupJob < ApplicationJob
  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 also configure the prefix on a per job basis.

class GuestsCleanupJob < ApplicationJob
  queue_as :low_priority
  self.queue_name_prefix = nil
  # ...
end

# Now your job's queue won't be prefixed, overriding what
# was configured in `config.active_job.queue_name_prefix`.

The default queue name prefix delimiter is '_'. This can be changed by setting config.active_job.queue_name_delimiter in application.rb:

# config/application.rb
module YourApp
  class Application < Rails::Application
    config.active_job.queue_name_prefix = Rails.env
    config.active_job.queue_name_delimiter = "."
  end
end

# app/jobs/guests_cleanup_job.rb
class GuestsCleanupJob < ApplicationJob
  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

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 it can access self.arguments), and it must return the queue name:

class ProcessVideoJob < ApplicationJob
  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)

If you want more control on what queue a job will be run you can pass a :queue option to set:

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

5. Priority

You can schedule a job to run with a specific priority using queue_with_priority:

class GuestsCleanupJob < ApplicationJob
  queue_with_priority 10
  # ...
end

Solid Queue, the default queuing backend, prioritizes jobs based on the order of the queues. You can read more about it in the Order of Queues section. If you're using Solid Queue, and both the order of the queues and the priority option are used, the queue order will take precedence, and the priority option will only apply within each queue.

Other queuing backends may allow jobs to be prioritized relative to others within the same queue or across multiple queues. Refer to the documentation of your backend for more information.

Similar to queue_as, you can also pass a block to queue_with_priority to be evaluated in the job context:

class ProcessVideoJob < ApplicationJob
  queue_with_priority do
    video = self.arguments.first
    if video.owner.premium?
      0
    else
      10
    end
  end

  def perform(video)
    # Process video
  end
end

ProcessVideoJob.perform_later(Video.last)

You can also pass a :priority option to set:

MyJob.set(priority: 50).perform_later(record)

6. Callbacks

Active Job provides hooks to trigger logic during the life cycle of a job. Like other callbacks in Rails, you can implement the callbacks as ordinary methods and use a macro-style class method to register them as callbacks:

class GuestsCleanupJob < ApplicationJob
  queue_as :default

  around_perform :around_cleanup

  def perform
    # Do something later
  end

  private
    def around_cleanup
      # Do something before perform
      yield
      # Do something after perform
    end
end

The macro-style class methods can also receive a block. Consider using this style if the code inside your block is so short that it fits in a single line. For example, you could send metrics for every job enqueued:

class ApplicationJob < ActiveJob::Base
  before_enqueue { |job| $statsd.increment "#{job.class.name.underscore}.enqueue" }
end

6.1. Available Callbacks

• before_enqueue
• around_enqueue
• after_enqueue
• before_perform
• around_perform
• after_perform

Please note that when enqueuing jobs in bulk using perform_all_later, callbacks such as around_enqueue will not be triggered on the individual jobs. See Bulk Enqueuing Callbacks.

7. Bulk Enqueuing

You can enqueue multiple jobs at once using perform_all_later. Bulk enqueuing reduces the number of round trips to the queue data store (like Redis or a database), making it a more performant operation than enqueuing the same jobs individually.

perform_all_later is a top-level API on Active Job. It accepts instantiated jobs as arguments (note that this is different from perform_later). perform_all_later does call perform under the hood. The arguments passed to new will be passed on to perform when it's eventually called.

Here is an example calling perform_all_later with GuestCleanupJob instances:

# Create jobs to pass to `perform_all_later`.
# The arguments to `new` are passed on to `perform`
guest_cleanup_jobs = Guest.all.map { |guest| GuestsCleanupJob.new(guest) }

# Will enqueue a separate job for each instance of `GuestCleanupJob`
ActiveJob.perform_all_later(guest_cleanup_jobs)

# Can also use `set` method to configure options before bulk enqueuing jobs.
guest_cleanup_jobs = Guest.all.map { |guest| GuestsCleanupJob.new(guest).set(wait: 1.day) }

ActiveJob.perform_all_later(guest_cleanup_jobs)

perform_all_later logs the number of jobs successfully enqueued, for example if Guest.all.map above resulted in 3 guest_cleanup_jobs, it would log Enqueued 3 jobs to Async (3 GuestsCleanupJob) (assuming all were enqueued).

The return value of perform_all_later is nil. Note that this is different from perform_later, which returns the instance of the queued job class.

7.1. Enqueue Multiple Active Job Classes

With perform_all_later, it's also possible to enqueue different Active Job class instances in the same call. For example:

class ExportDataJob < ApplicationJob
  def perform(*args)
    # Export data
  end
end

class NotifyGuestsJob < ApplicationJob
  def perform(*guests)
    # Email guests
  end
end

# Instantiate job instances
cleanup_job = GuestsCleanupJob.new(guest)
export_job = ExportDataJob.new(data)
notify_job = NotifyGuestsJob.new(guest)

# Enqueues job instances from multiple classes at once
ActiveJob.perform_all_later(cleanup_job, export_job, notify_job)

7.2. Bulk Enqueue Callbacks

When enqueuing jobs in bulk using perform_all_later, callbacks such as around_enqueue will not be triggered on the individual jobs. This behavior is in line with other Active Record bulk methods. Since callbacks run on individual jobs, they can't take advantage of the bulk nature of this method.

However, the perform_all_later method does fire an enqueue_all.active_job event which you can subscribe to using ActiveSupport::Notifications.

The method successfully_enqueued? can be used to find out if a given job was successfully enqueued.

7.3. Queue Backend Support

For perform_all_later, bulk enqueuing needs to be backed by the queue backend. Solid Queue, the default queue backend, supports bulk enqueuing using enqueue_all.

Other backends like Sidekiq have a push_bulk method, which can push a large number of jobs to Redis and prevent the round trip network latency. GoodJob also supports bulk enqueuing with the GoodJob::Bulk.enqueue method.

If the queue backend does not support bulk enqueuing, perform_all_later will enqueue jobs one by one.

8. Action Mailer

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

9. Internationalization

Each job uses the I18n.locale set when the job was created. This is useful if you send emails asynchronously:

I18n.locale = :eo

UserMailer.welcome(@user).deliver_later # Email will be localized to Esperanto.

10. Supported Types for Arguments

ActiveJob supports the following types of arguments by default:

• Basic types (NilClass, String, Integer, Float, BigDecimal, TrueClass, FalseClass)
• Symbol
• Date
• Time
• DateTime
• ActiveSupport::TimeWithZone
• ActiveSupport::Duration
• Hash (Keys should be of String or Symbol type)
• ActiveSupport::HashWithIndifferentAccess
• Array
• Range
• Module
• Class

10.1. GlobalID

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 < ApplicationJob
  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 < ApplicationJob
  def perform(trashable, depth)
    trashable.cleanup(depth)
  end
end

This works with any class that mixes in GlobalID::Identification, which by default has been mixed into Active Record classes.

10.2. Serializers

You can extend the list of supported argument types. You just need to define your own serializer:

# app/serializers/money_serializer.rb
class MoneySerializer < ActiveJob::Serializers::ObjectSerializer
  # Converts an object to a simpler representative using supported object types.
  # The recommended representative is a Hash with a specific key. Keys can be of basic types only.
  # You should call `super` to add the custom serializer type to the hash.
  def serialize(money)
    super(
      "amount" => money.amount,
      "currency" => money.currency
    )
  end

  # Converts serialized value into a proper object.
  def deserialize(hash)
    Money.new(hash["amount"], hash["currency"])
  end

  private
    # Checks if an argument should be serialized by this serializer.
    def klass
      Money
    end
end

and add this serializer to the list:

# config/initializers/custom_serializers.rb
Rails.application.config.active_job.custom_serializers << MoneySerializer

Note that autoloading reloadable code during initialization is not supported. Thus it is recommended to set-up serializers to be loaded only once, e.g. by amending config/application.rb like this:

# config/application.rb
module YourApp
  class Application < Rails::Application
    config.autoload_once_paths << "#{root}/app/serializers"
  end
end

11. Exceptions

Exceptions raised during the execution of the job can be handled with rescue_from:

class GuestsCleanupJob < ApplicationJob
  queue_as :default

  rescue_from(ActiveRecord::RecordNotFound) do |exception|
    # Do something with the exception
  end

  def perform
    # Do something later
  end
end

If an exception from a job is not rescued, then the job is referred to as "failed".

11.1. Retrying or Discarding Failed Jobs

A failed job will not be retried, unless configured otherwise.

It's possible to retry or discard a failed job by using retry_on or discard_on, respectively. For example:

class RemoteServiceJob < ApplicationJob
  retry_on CustomAppException # defaults to 3s wait, 5 attempts

  discard_on ActiveJob::DeserializationError

  def perform(*args)
    # Might raise CustomAppException or ActiveJob::DeserializationError
  end
end

11.2. 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.

12. Job Testing

You can find detailed instructions on how to test your jobs in the testing guide.

13. Debugging

If you need help figuring out where jobs are coming from, you can enable verbose logging.

14. Alternate Queuing Backends

Active Job has other 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.

14.1. Configuring the Backend

You can change your queuing backend with config.active_job.queue_adapter:

# config/application.rb
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

You can also configure your backend on a per job basis:

class GuestsCleanupJob < ApplicationJob
  self.queue_adapter = :resque
  # ...
end

# Now your job will use `resque` as its backend queue adapter, overriding the default Solid Queue adapter.

14.2. 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
• Resque
• Sneakers
• Queue Classic
• Delayed Job
• Que
• Good Job