Dockerfile for multi-stage build of a Ruby app which needs Node at build time (credits: https://github.com/gomex)

Dockerfile

# Dockerfile for a multi-stage build of a Ruby app which needs Node at build time
#
# Thanks to https://github.com/gomex for sharing

FROM ruby:2.5.1 as builder

RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - &&\
    curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - &&\
    echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list

ARG NODE_DATE_INSTALL=20180710

RUN apt-get update \
    && apt-get install -y locales \
                        graphviz \
                        imagemagick \
                        postgresql-client-9.6 \
                        yarn \
                        nodejs \
    && echo "en_US.UTF-8 UTF-8" > /etc/locale.gen && /usr/sbin/locale-gen &&\
    rm -rf /var/lib/apt/lists/*

ENV LANG en_US.UTF-8
ENV LANGUAGE en_US.UTF-8
ENV LC_ALL en_US.UTF-8
ARG BUNDLE_GITHUB__COM
ENV BUNDLE_GITHUB__COM $BUNDLE_GITHUB__COM
ENV GEM_HOME /gems/vendor
ENV GEM_PATH /gems/vendor
ENV GEM_SPEC_CACHE /gems/specs
ENV BUNDLE_APP_CONFIG /gems/vendor
ENV BUNDLE_PATH /gems/vendor
ENV BUNDLE_BIN /gems/vendor/bin
ENV PATH /app/bin:/gems/vendor/bin:$PATH
ARG RAILS_ENV
ENV RAILS_ENV=$RAILS_ENV

ENV APP_ROOT /app

WORKDIR $APP_ROOT/

RUN mkdir -p /gems

RUN groupadd -r app \
    && groupmod -g 1000 app \
    && useradd -g app -ms /bin/bash app \
    && chown app $APP_ROOT \
    && chown -R app /gems

USER app

FROM builder as install

USER app

COPY Gemfile.lock $APP_ROOT/
COPY Gemfile $APP_ROOT/
COPY package-lock.json $APP_ROOT/
COPY package.json $APP_ROOT/

RUN bundle install
RUN yarn install

FROM install as preprod

USER root

ARG SECRET_KEY_BASE
ENV SECRET_KEY_BASE=$SECRET_KEY_BASE

COPY . /$APP_ROOT/

RUN bundle exec rails assets:precompile


# Packaging final app w/o node_modules & the development tools
FROM paycertify/ruby:2.5.1-slim as prod

LABEL maintainer="Rafael Gomes <rafael.gomes@paycertify.com>"
LABEL name="app"

ENV GEM_HOME /gems/vendor
ENV GEM_PATH /gems/vendor
ENV GEM_SPEC_CACHE /gems/specs
ENV BUNDLE_APP_CONFIG /gems/vendor
ENV BUNDLE_PATH /gems/vendor
ENV BUNDLE_BIN /gems/vendor/bin
ENV PATH /app/bin:/gems/vendor/bin:$PATH

WORKDIR /app/

RUN groupadd -r app \
    && groupmod -g 1000 app \
    && useradd -g app -ms /bin/bash app

COPY --from=preprod /usr/local/bundle/ /usr/local/bundle/
COPY --from=preprod /app/ /app/
COPY --from=preprod /gems/ /gems/
RUN chown -R app /gems
RUN chown -R app /app/

USER app

EXPOSE 3000

CMD ["bundle","exec","rails","server","-b","0.0.0.0"]