Docker setup for Rails and PostgreSQL

docker_rails_setup.md

Docker :: Rails

Setup Process

Step 1 :: Install Docker Desktop

• Ensure the Docker desktop app is installed and running locally
  • https://www.docker.com/products/docker-desktop
• if you are starting a new Rails project follow this guide
  • https://docs.docker.com/compose/rails/
• else you are working with an existing Rails project
  • Proceed to Step 2

Step 2 :: Add or Edit files

• Add or edit the files listed below in the Files section
• Replace my_app with your application root directory name

Step 3 :: Disable Yarn Integrity

• Path
  • config/environments/development.rb
• Command to Add
  • config.webpacker.check_yarn_integrity = false
• Result
  • Solves yarn not found error

Step 4 :: Build Docker Images

• Build the application in Docker
  • Ensure your current terminal location is the my_app project root directory
  • $ docker-compose build
• When build is complete activate the application containers in Docker
  • $ docker-compose up
• Create the PostgreSQL database and run migrations. Open a new terminal
  • $ docker-compose run web rake db:create db:migrate

Step 5 :: RSpec Tests

• The application should be running locally on Docker. If not please check the steps above, or start them with
  • docker-compose up
• In a new terminal run this command
  • docker-compose exec web rspec
• Or this alternative command (if necessary)
  • docker-compose run -e "RAILS_ENV=test" web rspec
• Result
  • Solves not being able to run RSpec tests using bundle exec rspec or rspec
  • This will run RSpec tests using the active app and db containers

Step 6 (optional)

• Follow guide for integration with CircleCI
  • https://gist.github.com/iEv0lv3/0d3979312791f6a64440b3d320c0bea8

Files

Dockerfile :: Add to my_app root directory

# Replace Ruby version below with your application's Ruby version. Delete this comment.
FROM ruby:2.7.1
RUN apt-get update -qq && apt-get install -y nodejs postgresql-client
RUN mkdir /my_app
WORKDIR /my_app
COPY Gemfile /my_app/Gemfile
COPY Gemfile.lock /my_app/Gemfile.lock
RUN bundle install
COPY . /my_app

# Add a script to be executed every time the container starts.
COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
EXPOSE 3000

# Start the main process.
CMD ["rails", "server", "-b", "0.0.0.0"]

docker-compose.yml :: Add to my_app root directory

version: '3.1'
services:
  db:
    image: postgres
    restart: always
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
    environment:
      POSTGRES_PASSWORD: password
  web:
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/my_app
    ports:
      - "3000:3000"
    depends_on:
      - db

database.yml :: Edit file located at config/database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: postgres
  password: password
  host: db
  port: 5432

entrypoint.sh :: Add to my_app root directory

#!/bin/bash
set -e

# Remove a potentially pre-existing server.pid for Rails.
rm -f /my_app/tmp/pids/server.pid

# Then exec the container's main process (what's set as CMD in the Dockerfile).
exec "$@"

With your bash command in docker-compose, you don't need the entrypoint.sh in my_app right? Seems like one or the other??? Fighting with similar issue.

@epugh, that is correct, and I need to update that line; great catch! I am now exclusively using an entrypoint.sh file in both development and production instead of a CMD line in the Dockerfile. I find using the bash script produces consistent results when I deploy to GCP Cloud Run and Kubernetes.

I was having issues with other guides on dockerising Rails but this one worked perfectly and was clear and easy to follow, thank you!

Hi @iEvolv3
great guide, just had a question as to why are we copying the gemfile and gemfile.lock separately and then copying the entire application directory? and same goes for `entry point file.
Why don't we just copy the app directory that contains all these files?