How can i isolate Rails API and Rails workers job in diffrent containers docker

Question

I'm planning dockerize my existing Rails project.

My project has an API controller and worker to run jobs in background

Is there a way to separate my application in 3 parts using docker containers:

Eg:

• One Container for the application
• One Container for run Rails jobs
• One Container for the Rails API

I know that i can use one container for the application and another to database, but my question is about isolate the application.

Answer 1

Typically, your jobs will be saved to a backend- eg Redis for Sidekiq, some sql database for delayed_jobs. The actual execution of the jobs can be placed somewhere else.

In the web server's Dockerfile you might have the entry point written like this (example):

CMD ["bundle", "exec", "rails", "server", "-b", "0.0.0.0"]

This runs only the web-server. To be honest, I think the "application" and the API that you're talking about should run off the same container.

---

For the execution of the jobs, you can use the same image, but define a different entry point. (Check out docker-compose , it's really handy)

In there, you would ask it to.. start up some workers for instance, and that command would depend on which background processing gem you chose to go with. You will also need to pass it the configuration for the database that the jobs are stored in.

---

An sample docker-compose file that you might write might look like this:

version: '2'
services:
  redis:
    image: 'redis:3.2-alpine'
    command: redis-server
    ports:
      - 6379:6379
    volumes:
      - redis:/data

  app:
    depends_on:
      - redis
      - postgres (or some other db you have)
    build: .
    ports:
      - 3000:3000
    volumes:
      - .:/app

  sidekiq:
    depends_on:
      - redis
    build: .
    command: sidekiq -C config/sidekiq.yml.erb
    volumes:
      - .:/app