A simple Rails application configured for PostgreSQL and Docker

rails-docker-pg-template.rb

generate(:scaffold, "post", "title:string", "body:text")

route "root to: 'posts#index'"

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') %>
  password: <%= ENV.fetch('POSTGRES_PASSWORD') %>

development:
  <<: *default                                                                       
  database: my-app_development

test:
  <<: *default                                                                       
  database: my-app_test

production:
  <<: *default                                                                       
  database: my-app_production
CODE

file 'Dockerfile', <<-CODE
FROM ruby:2.3-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

# Bundle into the temp directory
WORKDIR /tmp
ADD Gemfile* ./

RUN apk add --virtual build-deps build-base openssl-dev 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 \
    RACK_ENV=production

# Expose port 3000 from the container
EXPOSE 3000

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