Introduction

In web applications, certain tasks can be slow and should not be executed in real-time—like sending emails, processing large files, or making API calls. Rails provides background job processing to handle these tasks asynchronously, improving performance and user experience.

In this guide, we’ll cover:
✅ Why you need background jobs
✅ How to use Active Job in Rails
✅ Popular background job libraries: Sidekiq, Delayed Job, and Resque
✅ Best practices for scaling background processing

1. Why Use Background Jobs?

Background tasks improve application performance by offloading slow operations.

🔹 Example Use Cases:

  • Sending emails (ActionMailer)
  • Generating reports
  • Uploading & processing files
  • Interacting with third-party APIs
  • Running periodic tasks (cron jobs)

2. Introducing Active Job

Rails provides Active Job, a built-in framework for handling background tasks consistently across different job queues.

2.1 Creating a Job

Generate a job using:

rails generate job ExampleJob

Edit app/jobs/example_job.rb:

class ExampleJob < ApplicationJob
queue_as :default

def perform(*args)
Rails.logger.info "Processing background job with args: #{args.inspect}"
end
end
2.2 Enqueueing a Job

Call the job in a controller or service:

ExampleJob.perform_later("Hello, background processing!")

This schedules the job for execution asynchronously.

3. Choosing a Background Job Processor

Active Job is queue-agnostic, meaning you can use it with different queue backends. Let’s compare the most popular options:

Processor Features & Use Cases
Sidekiq Fast, uses Redis, supports concurrency
Delayed Job Stores jobs in the database, simple to set up
Resque Uses Redis, supports multiple queues
GoodJob Uses PostgreSQL for queueing

4. Setting Up Sidekiq

Sidekiq is the most popular and fastest job processor, using Redis for background tasks.

4.1 Installing Sidekiq

Add to Gemfile:

gem 'sidekiq'

Run:

bundle install
4.2 Configuring Sidekiq

Update config/application.rb:

config.active_job.queue_adapter = :sidekiq

Add config/sidekiq.yml:

:concurrency: 5
:queues:
- default
- mailers
4.3 Running Sidekiq

Start Redis:

redis-server

Run Sidekiq:

bundle exec sidekiq

5. Using Delayed Job

Delayed Job is simple and stores jobs in the database.

5.1 Installing Delayed Job

Add to Gemfile:

gem 'delayed_job_active_record'

Run:

bundle install
rails generate delayed_job:active_record
rails db:migrate
5.2 Using Delayed Job

Run a task asynchronously:

UserMailer.welcome_email(@user).deliver_later

Start the worker:

rails jobs:work

6. Monitoring and Managing Jobs

You can monitor jobs in production using Sidekiq’s web UI or database tools.

6.1 Sidekiq Web UI

Add to routes.rb:

require 'sidekiq/web'
mount Sidekiq::Web => "/sidekiq"

Visit http://localhost:3000/sidekiq to view and manage jobs.

6.2 Monitoring Delayed Job

Check failed jobs:

rails jobs:failed

7. Best Practices for Background Jobs

✅ Use priority queues – Assign different tasks to default, mailers, low_priority queues
✅ Monitor job failures – Use Sidekiq UI or logs
✅ Avoid long-running jobs – Break them into smaller tasks
✅ Use retries wisely – Sidekiq retries failed jobs by default
✅ Secure sensitive data – Don’t store private data in job arguments

Conclusion

Managing background tasks in Rails improves application performance by offloading slow operations.
🔹 Use Active Job for a unified API
🔹 Sidekiq for high-performance tasks
🔹 Delayed Job for simple database-backed jobs
🔹 Monitor jobs to prevent failures

Start using background jobs today to make your Rails apps faster and more efficient! 🚀