Rails Docker Configuration

.env

DATABASE_USER=gugus
DATABASE_PASSWORD=gugus
RAILS_ENV=development
RACK_ENV=development
BUNDLE_PATH=/usr/local/bundle
USER_ID=1000
GROUP_ID=990

docker-compose.yml

version: '3'
services:
  app:
    build: .
    command: bundle exec rails server -p 3000 -b '0.0.0.0'
    environment:
    - 'RAILS_ENV=${RAILS_ENV}'
    - 'RACK_ENV=${RACK_ENV}'
    - 'DATABASE_USER=${DATABASE_USER}'
    - 'DATABASE_PASSWORD=${DATABASE_PASSWORD}'
    - 'BUNDLE_PATH=${BUNDLE_PATH}'
    hostname: sententia
    volumes:
    - .:/app
    user: '${USER_ID}:${GROUP_ID}'
    ports:
    - '3000:3000'
    depends_on:
    - database
  database:
    hostname: database
    image: postgres:10.4-alpine
    environment:
    - 'POSTGRES_USER=${DATABASE_USER}'
    - 'POSTGRES_PASSWORD=${DATABASE_PASSWORD}'
    user: '${USER_ID}:${GROUP_ID}'
    volumes:
    - ./tmp/db:/var/lib/postgresql/data:z

Dockerfile

FROM ruby:2.5.1-alpine
RUN apk add --no-cache --update build-base \
                                linux-headers \
                                git \
                                postgresql-dev \
                                nodejs \
                                yarn \
                                tzdata
RUN mkdir -p /app
WORKDIR /app

COPY Gemfile /app/Gemfile
COPY Gemfile.lock /app/Gemfile.lock
RUN gem install bundler && bundle install --jobs 20 --retry 5

COPY . /app