Dockerfile

FROM ruby:2.7-slim-buster

WORKDIR /rails_app

RUN rm -f /etc/apt/apt.conf.d/docker-clean; echo 'Binary::apt::APT::Keep-Downloaded-Packages "true";' > /etc/apt/apt.conf.d/keep-cache

RUN --mount=type=cache,id=talk-apt-cache,target=/var/cache/apt --mount=type=cache,id=talk-apt-lib,target=/var/lib/apt \
    apt-get update && \
    apt-get install --no-install-recommends -y \
    build-essential \
    git \
    libpq-dev \
    tmpreaper

ARG RAILS_ENV=production

ADD ./Gemfile /rails_app/
ADD ./Gemfile.lock /rails_app/

RUN bundle config --global jobs `cat /proc/cpuinfo | grep processor | wc -l | xargs -I % expr % - 1`
RUN if [ "$RAILS_ENV" = "development" ]; then bundle install; else bundle install --without development test; fi

ADD ./ /rails_app

RUN (git log --format="%H" -n 1 > /rails_app/public/commit_id.txt && rm -rf .git)

EXPOSE 81

CMD [ "/rails_app/docker/start.sh" ]