Felipe Gentil | Using pry/byebug inside a Docker container

Using pry/byebug inside a Docker container

04 Oct 2016

docker ruby

Quick tip for Ruby developer who are using Docker and can’t debug their code with pry. For those who don’t know, pry is an awesome IRB shell for Ruby…

This is a simple .docker-compose.yml file with a web app and a MySql database.

web:
  build: .
  volumes:
    - .:/myapp
  ports:
    - "3000:3000"
  links:
    - db:db
db:
  image: mysql
  environment:
    MYSQL_ROOT_PASSWORD: abc123
  ports:
    - "3306:3306"

All you have to do is run your container with the following command:

$ docker-compose run --service-ports web

This is my HomeController

class HomeController < ApplicationController
    def index
        binding.pry
    end
end

Trying things out

$ curl localhost:3000

From: /myapp/app/controllers/home_controller.rb @ line 3 HomeController#index:

    2: def index
 => 3:     binding.pry
    4: end

[1] pry(#<HomeController>)>

It is important to notice that it works also with byebug

[1, 5] in /myapp/app/controllers/home_controller.rb
   1: class HomeController < ApplicationController
   2:     def index
   3:         byebug
=> 4:     end
   5: end
(byebug)

Hope it helps :)