medium-multi-stage-dockerfile-compiler-stage

Dockerfile

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# Stage compiler
FROM runner as compiler
LABEL description="Builds a compiler image used to compile assets"

# Copy cached compiled assets to avoid re-compiling them
# We use latest compiler image to get already compiled assets
# and save lots of time on assets compilation for this new image
COPY --chown=app:app --from=my-app:compiler /home/app/public /home/app/public
COPY --chown=app:app --from=my-app:compiler /home/app/tmp /home/app/tmp

# Env variables required to run rake assets:precompile
ARG ASSET_HOST
ARG ENV=production

# Precompile assets and keep the cache for future releases
RUN ASSET_HOST=$ASSET_HOST \
    RAILS_ENV=$ENV \
    bundle exec rake assets:precompile