RailsHow-ToBeginner · 3 min read

How to Use Active Job in Rails: Simple Guide with Examples

In Rails, use Active Job by creating a job class that inherits from ApplicationJob and defining a perform method with the task code. Then enqueue the job with perform_later to run it asynchronously in the background.

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Syntax

To use Active Job, create a job class inheriting from ApplicationJob. Define a perform method with the code you want to run in the background. Use perform_later to enqueue the job asynchronously.

class YourJob < ApplicationJob: Defines the job class.
perform(*args): Contains the background task code.
perform_later(*args): Enqueues the job to run later.

ruby

class ExampleJob < ApplicationJob
  queue_as :default

  def perform(*args)
    # Your background task code here
  end
end

# To enqueue the job:
ExampleJob.perform_later('argument')

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Example

This example shows a job that sends a welcome email asynchronously. The perform method calls the mailer, and perform_later queues the job.

ruby

class WelcomeEmailJob < ApplicationJob
  queue_as :default

  def perform(user_id)
    user = User.find(user_id)
    UserMailer.welcome_email(user).deliver_now
  end
end

# Enqueue the job to send email later
WelcomeEmailJob.perform_later(1)

Output

The job is enqueued and the welcome email is sent in the background without blocking the main app flow.

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Common Pitfalls

Common mistakes include calling perform directly instead of perform_later, which runs the job immediately and blocks the request. Another is forgetting to configure a queue adapter, so jobs never run.

Always set a queue adapter like config.active_job.queue_adapter = :async in config/application.rb or use a production-ready adapter like Sidekiq.

ruby

class BadJob < ApplicationJob
  def perform
    puts 'This runs immediately, blocking the request'
  end
end

# Wrong: runs immediately
BadJob.perform

# Right: runs in background
BadJob.perform_later

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Quick Reference

Action	Code Example	Description
Create job class	class MyJob < ApplicationJob; def perform; end; end	Defines a background job
Enqueue job	MyJob.perform_later(args)	Runs job asynchronously
Run job immediately (not recommended)	MyJob.perform(args)	Runs job synchronously
Set queue adapter	config.active_job.queue_adapter = :sidekiq	Configures job backend
Define queue	queue_as :mailers	Assigns job to a specific queue

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Key Takeaways

Create jobs by inheriting from ApplicationJob and defining perform method.

Use perform_later to enqueue jobs for background execution.

Configure a queue adapter to ensure jobs run properly.

Avoid calling perform directly to prevent blocking requests.

Assign jobs to queues for better organization and processing.