Dockerfile

FROM ruby:2.5.1-alpine AS base

# Set a variable for the install location.
ARG RAILS_ROOT=/usr/src/app
# Set Rails environment.
ENV RAILS_ENV production
ENV BUNDLE_APP_CONFIG="$RAILS_ROOT/.bundle"

# Make the directory and set as working.
RUN mkdir -p $RAILS_ROOT
WORKDIR $RAILS_ROOT

ARG BUILD_PACKAGES="build-base curl-dev git"
ARG DEV_PACKAGES="postgresql-dev sqlite-libs sqlite-dev yaml-dev zlib-dev nodejs yarn"
ARG RUBY_PACKAGES="tzdata"

# Install app dependencies.
RUN apk update \
    && apk upgrade \
    && apk add --update --no-cache $BUILD_PACKAGES $DEV_PACKAGES $RUBY_PACKAGES

COPY Gemfile* ./
COPY Gemfile Gemfile.lock $RAILS_ROOT/

RUN bundle config --global frozen 1 \
    && bundle install --deployment --without development:test:assets -j4 --path=vendor/bundle \
    && rm -rf vendor/bundle/ruby/2.5.0/cache/*.gem \
    && find vendor/bundle/ruby/2.5.0/gems/ -name "*.c" -delete \
    && find vendor/bundle/ruby/2.5.0/gems/ -name "*.o" -delete

# Adding project files.
COPY . .

# Remove folders not needed in resulting image
RUN rm -rf tmp/cache spec

############### Build step done ###############

FROM ruby:2.5.1-alpine

# Set a variable for the install location.
ARG RAILS_ROOT=/usr/src/app
ARG PACKAGES="tzdata curl postgresql-client sqlite-libs yarn nodejs bash"

ENV RAILS_ENV=production
ENV BUNDLE_APP_CONFIG="$RAILS_ROOT/.bundle"

WORKDIR $RAILS_ROOT

RUN apk update \
    && apk upgrade \
    && apk add --update --no-cache $PACKAGES


COPY --from=base $RAILS_ROOT $RAILS_ROOT

# Expose port 80.
EXPOSE 80

# Sets the footer of greenlight application with current build version
ARG version_code
ENV VERSION_CODE=$version_code

# Start the application.
CMD ["bin/start"]