This is an example and tutorial to build and run your Rails app on Docker.

Preparation

You need followings:

• Docker installed: Link
• Docker compose installed: Link

Run project

Up Docker container.

$ docker-compose up

Initialize database (First time only)

Open another console

Keep the Docker containers running.

While they are running, you need to open a new console to work.

In the 2nd console just you opened, type following line to create database while running docker-compose up in the 1st one.

$ docker-compose exec rails rake db:create
Created database 'recipe_development'
Created database 'recipe_test'

$ docker-compose exec rails rake db:migrate

$ docker-compose exec rails rake db:seed

Open in browser

Open http://localhost:8080/ and look at what you have done! Yay! You’re on Rails!

Open in AWS cloud9 preview

1. Click Preview button
2. Choose Preview running application
3. Click Pop out into new Window (up-right corner)

PhpAdmin

PhpAdmin running at port 8081 ( http://localhost:8081/ or :8081 port relative to cloud9 domain )

User: root

Password: root

Up your project from the next time

Now it's simple.

$ docker-compose up

And open http://localhost:8080/.

Stop docker server

Try to stop the containers by holding Ctrl-C in the console. Closing process may take time. Be patient.

Gracefully stopping... (press Ctrl+C again to force)
Stopping docker-rails-example_rails_1   ... done
Stopping docker-rails-example_db_1      ... done

$

Update your project

General idea

You may want to run rails, rake or any other commands. For those cases, the most basic idea is running docker-compose exec rails xxx.

Let's say you want to echo here. You would use this:

$ docker-compose exec rails echo Hello from Docker container!

Please remember you have to type this command into your 2nd console, next the 1st one where your docker-compose up is running.

When you want to generate a scaffold

$ docker-compose exec rails rails g scaffold post title:string body:text
      invoke  active_record
      create    db/migrate/20180806212720_create_posts.rb
      create    /models/post.rb
...
      create      /assets/stylesheets/posts.scss
      invoke  scss
      create    /assets/stylesheets/scaffolds.scss

Don't forget migration! (See next chapter.)

When you generated a new migration

$ docker-compose exec rails rake db:migrate
== 20180806212720 CreatePosts: migrating ======================================
-- create_table(:posts)
   -> 0.0766s
== 20180806212720 CreatePosts: migrated (0.0769s) =============================

When you want to run test

$ docker-compose exec rails rake test
Run options: --seed 52703

# Running:

.......

Finished in 1.302024s, 5.3762 runs/s, 6.9123 assertions/s.
7 runs, 9 assertions, 0 failures, 0 errors, 0 skips

When you added new gems

When you update Gemfile, you used to run bundle install.

With Docker, you need to rebuild your image instead. This process includes bundle install and updates Gemfile.lock.

To rebuild, give --force-recreate option.

$ docker-compose.exe up --build

Otherwise you would see an error like this (you could miss it because the log is too long to read):

rails_1  | /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.7/lib/bundler/resolver.rb:366:in `block in verify_gemfile_dependencies_are_found!': Could not find gem 'carrierwave' in any of the gem sources listed in your Gemfile or available on this machine. (Bundler::GemNotFound)
rails_1  |      from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.7/lib/bundler/resolver.rb:341:in `each'
...
rails_1  |      from /usr/local/bundle/bin/rails:15:in `<main>'

Enter container bash

$ docker-compose exec rails bash

Exit container bash

root@9c8cecc436ff:/app# exit