Docker multi-stage builds with the GOV.UK Design system (2018)

application.scss

// …

// Override any GOVUK settings here
// use Rails asset helpers
$govuk-font-url-function: 'font-url';
$govuk-image-url-function: 'image-url';

assets.rb

# Be sure to restart your server when you modify this file.

# Version of your assets, change this if you want to expire all your assets.
Rails.application.config.assets.version = '1.0'

# GOV.UK Design system
# Add additional assets to the asset load path.
Rails.application.config.assets.paths << Rails.root.join('node_modules')
Rails.application.config.assets.precompile += %w[
  govuk-frontend/all.js
  govuk-frontend/all.scss
  govuk-frontend/all-ie8.scss
]

# Precompile additional assets.
# application.js, application.css, and all non-JS/CSS in the app/assets
# folder are already added.
Rails.application.config.assets.precompile +=
  %w[application.css application-ie8.css application.js]

docker-compose.yml

version: '3'
services:
  web:
    build:
      context: .
      args:
        RAILS_ENV: "development"
    ports: ["3000:3000"]
    environment:
      RAILS_ENV: "development"
    env_file:
      - docker-compose.env
    depends_on:
      - db
      - elasticsearch
      - redis
    tty: true
    stdin_open: true
    restart: on-failure
    volumes:
      - .:/srv/dfe-tvs:cached
      - node_modules:/srv/dfe-tvs/node_modules # <--- Don't reset node_modules with your working directory as it will empty it
    command: bash -c "rm -f tmp/pids/server.pid && rails s -b 'ssl://web:3000?key=config/localhost/https/local.key&cert=config/localhost/https/local.crt'"

  db:
    image: postgres
    volumes:
      - pg_data:/var/lib/postgresql/data/:cached
    restart: on-failure

  elasticsearch:
    image: elasticsearch
    depends_on:
      - db
    ports:
      - "9200:9200"
    environment:
      - discovery.type=single-node
      - cluster.name=docker=docker-cluster
    volumes:
      - elasticsearch:/usr/share/elasticsearch/data
    restart: on-failure

  redis:
    image: redis:latest
    command: redis-server

volumes:
  pg_data: {}
  elasticsearch: {}
  node_modules: <--- You need this for the above to work too :)

Dockerfile

# Install dependencies into a seperate and isolated Docker stage
# that is thrown away apart from any subsequent COPY commands
FROM mkenney/npm:latest AS dependencies
ENV INSTALL_PATH /deps
RUN mkdir -p $INSTALL_PATH
WORKDIR $INSTALL_PATH
COPY package.json ./package.json
COPY package-lock.json ./package-lock.json
RUN npm set progress=false && npm config set depth 0
RUN npm install --only=production

FROM ruby:2.4.0 as release
MAINTAINER dxw <rails@dxw.com>
RUN apt-get update && apt-get install -qq -y \
  build-essential \
  nodejs \
  libpq-dev \
  --fix-missing --no-install-recommends

ENV PHANTOM_JS="phantomjs-2.1.1-linux-x86_64"
RUN curl -OLk https://bitbucket.org/ariya/phantomjs/downloads/$PHANTOM_JS.tar.bz2
RUN tar xvjf $PHANTOM_JS.tar.bz2
RUN mv $PHANTOM_JS/bin/phantomjs /usr/local/bin/phantomjs
RUN rm -rf $PHANTOM_JS

ENV INSTALL_PATH /srv/dfe-tvs
RUN mkdir -p $INSTALL_PATH

# This must be ordered before rake assets:precompile
COPY --from=dependencies ./deps/node_modules $INSTALL_PATH/node_modules
COPY --from=dependencies ./deps/node_modules/govuk-frontend/assets $INSTALL_PATH/app/assets

WORKDIR $INSTALL_PATH

# set rails environment
ARG RAILS_ENV
ENV RAILS_ENV=${RAILS_ENV:-production}
ENV RACK_ENV=${RAILS_ENV:-production}

COPY Gemfile $INSTALL_PATH/Gemfile
COPY Gemfile.lock $INSTALL_PATH/Gemfile.lock

RUN gem install bundler

# bundle ruby gems based on the current environment, default to production
RUN echo $RAILS_ENV
RUN \
  if [ "$RAILS_ENV" = "production" ]; then \
    bundle install --without development test --retry 10; \
  else \
    bundle install --retry 10; \
  fi

COPY . $INSTALL_PATH

RUN bundle exec rake DATABASE_URL=postgresql:does_not_exist --quiet assets:precompile

COPY ./docker-entrypoint.sh /
RUN chmod +x /docker-entrypoint.sh
EXPOSE 3000

ENTRYPOINT ["/docker-entrypoint.sh"]
CMD ["rails", "server"]