A simple Rails application configured for PostgreSQL and Docker

rails-docker-pg-template.rb

route "root to: 'posts#index'"

generate :scaffold, 'post', 'title:string', 'body:text'

file 'config/database.yml', <<-CODE
default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  host: db
  username: <%= ENV.fetch('POSTGRES_USER') { 'postgres' } %>
  password: <%= ENV.fetch('POSTGRES_PASSWORD') { 'secret123' } %>
development:
  <<: *default
  database: my-app_development
test:
  <<: *default
  database: my-app_test
production:
  <<: *default
  database: my-app_production
CODE

file 'Dockerfile', <<-CODE
FROM ruby:2.6-alpine
# Set local timezone
RUN apk add --update tzdata &&     cp /usr/share/zoneinfo/Europe/London /etc/localtime &&     echo "Europe/London" > /etc/timezone

# Install your app's runtime dependencies in the container
RUN apk add --update --virtual runtime-deps postgresql-client nodejs libffi-dev readline sqlite xz-libs

# Install Yarn
ENV PATH=/root/.yarn/bin:$PATH
RUN apk add --virtual build-yarn curl && \
    touch ~/.bashrc && \
    curl -o- -L https://yarnpkg.com/install.sh | sh && \
    apk del build-yarn

# Bundle into the temp directory
WORKDIR /tmp
ADD Gemfile* ./
RUN apk add --virtual build-deps build-base postgresql-dev libc-dev linux-headers libxml2-dev libxslt-dev readline-dev &&     bundle install --jobs=2 &&     apk del build-deps

# Copy the app's code into the container
ENV APP_HOME /app
COPY . $APP_HOME
WORKDIR $APP_HOME

# Configure production environment variables
ENV RAILS_ENV=production
ENV RACK_ENV=production

# Precompile assets into the container
RUN bin/rails webpacker:install
RUN bin/rails assets:precompile

# Expose port 3000 from the container
EXPOSE 3000

# Run puma server by default
CMD ["bundle", "exec", "puma", "-C", "config/puma.rb"]
CODE