====== Dockerfile
# Base image:
FROM ruby:2.4.2

# Install dependencies
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs software-properties-common
RUN apt-get update -qq && apt-get install -y imagemagick

# Set an environment variable where the Rails app is installed to inside of Docker image:
ENV RAILS_ROOT /thegame
#ENV RAILS_ENV production
RUN mkdir -p $RAILS_ROOT

# Set working directory, where the commands will be ran:
WORKDIR $RAILS_ROOT

# Gems:
COPY Gemfile Gemfile.lock ./
RUN gem install bundler && bundle install --jobs 20 --retry 5
RUN gem list activerecord

ADD config/puma.rb config/puma.rb

# Copy the main application.
COPY . .

EXPOSE 3000



====== docker-compose.prod.yml
version: '2'
services:
  postgres:
    image: postgres:9.4.5
    environment:
      POSTGRES_USER: thegame
      POSTGRES_PASSWORD: thegame
    ports:
      - '5435:5432'
    volumes:
      - thegame-postgres:/var/lib/postgresql/data
  app:
    build:
      context: .
      dockerfile: Dockerfile.prod
    command: ./entrypoint
    volumes:
      - .:/thegame
    ports:
      - "3010:3000"
    env_file:
      - .env.production
volumes:
  thegame-postgres:



====== entrypoint
#!/bin/bash
set -e
if [[ -a /tmp/puma.pid ]]; then
  rm /tmp/puma.pid
fi

if [[ \$RAILS_ENV == "production" ]]; then
  rake assets:precompile
fi

rails server -b 0.0.0.0 -P /tmp/puma.pid -p 3000
exec "\$@"