Job Processing

What is Async::Job?

Async::Job is a framework for creating background jobs that run asynchronously without blocking web requests. It integrates seamlessly with Rails' ActiveJob, allowing you to offload long-running tasks to background workers. The Rails integration uses a specific gem to provide this functionality, called async-job-adapter-active_job.

When to use async jobs:

• Long-running tasks (data processing, file uploads).
• Email sending and external API calls.
• Scheduled tasks and periodic jobs.
• Heavy computations that would slow down web responses.

When NOT to use async jobs:

• Simple operations that complete quickly.
• Tasks that need immediate user feedback.

Basic Implementation

Server-Side: Job Class

Create a job class that inherits from ApplicationJob:

class MyJob < ApplicationJob
	# Specify the queue adapter per-job rather than globally:
	# queue_adapter :async_job
	
	queue_as "default"
	
	def perform
		# ... work ...
	end
end

Key Points:

• Use queue_as to specify which queue this job should use.
• The perform method contains your background work.

Configuration

Configure async-job queues in config/initializers/async_job.rb:

require "async/job"
require "async/job/processor/aggregate"
require "async/job/processor/redis"
require "async/job/processor/inline"

Rails.application.configure do
	config.async_job.define_queue "default" do
		# Double-buffers incoming jobs to avoid submission latency:
		enqueue Async::Job::Processor::Aggregate
		dequeue Async::Job::Processor::Redis
	end
	
	config.async_job.define_queue "local" do
		dequeue Async::Job::Processor::Inline
	end
end

Key Points:

• default queue uses Redis for persistent job storage.
• local queue processes jobs inline, but in a background Async task - higher throughput but lower robustness.
• Different processors can be used for different queue behaviors.

Configure the default adapter in config/application.rb:

# ... in the application configuration:
config.active_job.queue_adapter = :async_job

Key Points:

• This sets Async::Job as the default queue adapter. You can instead specify this per-job for incremental migration.