David Bourea

David Boureau

I create web applications

Rails 6 and Active Job tutorial

14 July, 2020

1. Overview

Active Job is a feature of the Ruby-on-Rails framework, that allows you to launch heavy jobs in the background.

For example, scraping or mailing are these kind of jobs, that are

They are the exact opposite of the request/response pattern of your web server, that is fast, synchronous, and launched at anytime.

A serious drawback is requires a lot more tooling than the “rails new” command offers.

Even building the simplest “hello world” job is not that simple.

This tutorial is dedicated to those who

2. Steps to reproduce

2a. Prerequisites

$> git --version
git version 2.7.2
$> docker -v
Docker version 17.12.0-ce
$> docker-compose -v
docker-compose version 1.18.0

Any upper version should work

2b. Installation

~/workspace/$ git clone https://github.com/bdavidxyz/rails_sidekiq_docker

~/workspace/$ cd rails_sidekiq_docker

~/workspace/rails_sidekiq_docker$> docker-compose build
... build images

~/workspace/rails_sidekiq_docker$> docker-compose run --rm --no-deps web rails new . --skip --database=postgresql
... create new rails project

~/workspace/rails_sidekiq_docker$> ./.dockerdev/post_build.sh
... create and modify some files

~/workspace/rails_sidekiq_docker$> docker-compose up

Now go to localhost:3000/sidekiq

Hurray ! You can monitor every job.

I suggest you to see in more details docker-compose, to see how all the tools talks to each other.

I also suggest to go to every file created or modified by post_build.sh

3. Create a “hello world” job

create file app/jobs/hello_world_job.rb

# app/jobs/hello_world_job.rb
class HelloWorldJob < ApplicationJob
  queue_as :default

  def perform(*args)
    p 'hello from HelloWorldJob'


modify file app/controllers/welcome_controller.rb to call your job

# app/controllers/welcome_controller.rb
class WelcomeController < ApplicationController
  def index
    HelloWorldJob.set(wait: 15.seconds).perform_later

Now go to localhost:3000, it will ask to enqueue the HelloWorldJob since the request goes through WelcomeController#index function.

Now go to localhost:3000/sidekiq, you will see the job in the “scheduled” section.

After a few seconds, it appears in the “Processed” section

4. Conclusion

We have built a working “hello world” job in less than 3 minutes, without side-effects, with all required tooling and configuration.

Enjoy !