Boilerplate to jump start a new rails application in docker and docker-compose

.dockerignore

# Ignore all logfiles and tempfiles.
/log/*
/tmp/*
/public/packs/*
!/log/.keep
!/tmp/.keep
.DS_Store
.env.development
.env.staging

# Ignore node_modules
/node_modules/*

# Ignore bundler config.
/.bundle

# Ignore the tags file used by VIM
tags

# Ignore Byebug command history file.
.byebug_history

# Ignore .git as it's not needed with the docker built.
.git
.cache

readme_boilerplate.md

Rails + Docker Compose project seed

This is a minimal setup to start a new Rails project

Assumptions:

1. Postgresql as a database
2. Webpacker as asset manager
3. Stimulusjs as js framework

Steps

Use the Dockerfile to build the rails image

docker-compose build

Run rails new command inside the container you just created

docker-compose run app rails new . --force --webapck=stimulus --database=postgresql

Start the db and rails images

docker-compose up

On a different console, copy the db config with username, and create the db:

cp database.sample.yml config/database.yml

docker-compose run app rails db:create

Now you can visit http://localhost:3000 and see your pristine rails 6 up & running

database.sample.yml

# PostgreSQL. Versions 9.3 and up are supported.
#
# Install the pg driver:
#   gem install pg
# On macOS with Homebrew:
#   gem install pg -- --with-pg-config=/usr/local/bin/pg_config
# On macOS with MacPorts:
#   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
# On Windows:
#   gem install pg
#       Choose the win32 build.
#       Install PostgreSQL and put its /bin directory on your path.
#
# Configure Using Gemfile
# gem 'pg'
#
default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see Rails configuration guide
  # https://guides.rubyonrails.org/configuring.html#database-pooling
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: postgres
  host: db

development:
  <<: *default
  database: app_development

  # The specified database role being used to connect to postgres.
  # To create additional roles in postgres see `$ createuser --help`.
  # When left blank, postgres will use the default role. This is
  # the same name as the operating system user that initialized the database.
  #username: app

  # The password associated with the postgres role (username).
  #password:

  # Connect on a TCP socket. Omitted by default since the client uses a
  # domain socket that doesn't need configuration. Windows does not have
  # domain sockets, so uncomment these lines.
  #host: localhost

  # The TCP port the server listens on. Defaults to 5432.
  # If your server runs on a different port number, change accordingly.
  #port: 5432

  # Schema search path. The server defaults to $user,public
  #schema_search_path: myapp,sharedapp,public

  # Minimum log levels, in increasing order:
  #   debug5, debug4, debug3, debug2, debug1,
  #   log, notice, warning, error, fatal, and panic
  # Defaults to warning.
  #min_messages: notice

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: app_test

# As with config/credentials.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
#   DATABASE_URL="postgres://myuser:mypass@localhost/somedatabase"
#
# You can use this database configuration with:
#
#   production:
#     url: <%= ENV['DATABASE_URL'] %>
#
production:
  <<: *default
  database: app_production
  username: app
  password: <%= ENV['APP_DATABASE_PASSWORD'] %>

docker-compose.yml

version: '3'
services:
  db:
    image: postgres
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
    environment:
      POSTGRES_HOST_AUTH_METHOD: "trust"
  app:
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    environment:
      BUNDLE_PATH: /bundle
    volumes:
      - .:/usr/src/app
      - .bundle:/bundle
    ports:
      - "3000:3000"
    depends_on:
      - db

Dockerfile

FROM ruby:2.7

# Ensure latest packages for Yarn
RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add -
RUN echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list

RUN apt-get update -yqq \
    && apt-get install -yqq --no-install-recommends \
      nodejs \
      yarn \
      postgresql-client \
    && rm -rf /var/lib/apt/lists/*

WORKDIR /usr/src/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"]

COPY Gemfile* ./
RUN bundle install --verbose --jobs 20 --retry 5

COPY . .

EXPOSE 3000
CMD ["rails", "server", "-b", "0.0.0.0"]

entrypoint.sh

#!/bin/bash
set -e

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

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

Gemfile

source 'https://rubygems.org'

# This will be overwritten by `rails new`
gem 'rails', '~> 6'