This tutorial is intended to be a quick guide. Create a new Rails application via Docker with the following Command docker run -it ruby:3.0.2 gem install rails bundler \ && rails new exampleapp -d=postgresql --webpack:react --skip-coffee Once the application is created, go to the application directory. All application files will be found there. cd exampleapp Create a File called Dockerfile with the Following Content // dockerfile FROM ruby:3.0.2 RUN apt-get update -qq \ && apt-get install -y curl build-essential libpq-dev \ nodejs postgresql-client &&\ curl -sL https://deb.nodesource.com/setup_10.x | bash - && \ curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - && \ echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list && \ apt-get update && apt-get install -y nodejs yarn ADD . /app WORKDIR /app RUN bundle install EXPOSE 3000 CMD ["bash"] This file will help Docker Compose build an image with all the needed dependencies installed to handle Rails. It will use Postgresql as a database engine and React bundled with webpack. Create a File Called docker-compose.yml With the Following Content version: '3.8' services: db: env_file: .env image: postgres web: build: . command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'" volumes: - .:/app ports: - "3000:3000" depends_on: - db env_file: .env environment: RAILS_ENV: development RAILS_MAX_THREADS: 5 volumes: postgres: Create a .env File Add the following environment variables. Pay special attention to the variable names since the image will need them for a proper setup, as well as the DATABASE_URL, which is needed by The query strings need to match with the other variable’s values. In the , the host is , which is the name exposed by Docker Compose. POSTGRES_ pg web. DATABASE_URL db POSTGRES_DB=postgres POSTGRES_USER=postgres POSTGRES_PASSWORD=secret DATABASE_URL=postgres://postgres:secret@db:5432/postgres Edit Database.yml Edit the file and add Here is an example of a valid config file for this tutorial. Keep in mind the way you expose sensitive data and the environments you are building the Docker Compose for. config/database.yml url: <%= ENV.fetch("DATABASE_URL") { '' } %> default: &default adapter: postgresql encoding: unicode pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %> url: <%= ENV.fetch("DATABASE_URL") { '' } %> # This is the line we added development: <<: *default database: exampleapp_development test: <<: *default database: exampleapp_test production: <<: *default database: exampleapp_production username: exampleapp password: <%= ENV['EXAMPLEAPP_DATABASE_PASSWORD'] %> Start the App The application is ready. We can start our application now. We are adding the parameter the first time, so that Docker Compose builds the containers first. --build docker-compose up --build Go to Localhost We can now go to in our browser. We should see the “Yay! You’re on Rails!” screen. http://localhost:3000 Now we can run commands (for example, generators and migrations) to evolve our application. We will now create a model with their controller and views, and then run a migration in this example. The model will be , and will have a name (string) and a value (float). Coin docker-compose run web rails g scaffold Coin name:string value:float \ && rails db:migrate Here is a quick video of all that we have seen until now.
