Different conditionals on the same Dockerfile - docker

Question

I have a Dockerfile with some commands I would like to use conditionally:
FROM + image_name (I have a M1 chip MacOS so I need to add --platform=linux/amd64 to it but I want to deploy in a AWS EC2 linux instance that doesn't need it)
On production I would like to run my project with nginx so I want the Dockerfile to end with this RUN mkdir -p tmp/sockets. But for testing, I have no need of the nginx so I would like my Dockerfile to end with this
# Expose port
EXPOSE 3000
# Start rails
CMD ["rails", "server", "-b", "0.0.0.0"]
I thought of using the multi stage dockerfile to solve the FROM image problem but the Dockerfile resulting is quite lengthy since it is basically the same except for the FROM image part.
For the nginx part I wanted to use a shell script but I am not sure how to write the exposing port and final command to start rails.
These are the files:
run_dockerfile.sh
#!/bin/bash
if [ ${RUN_DOCKERFILE} = "PROD" ]; then
mkdir -p tmp/sockets
else
????
fi
My Dockerfilelooks like this:
# Start from the official ruby image
# To run Dockerfile with arm64 architecture (M1 chip MacOS for example)
FROM --platform=linux/amd64 ruby:2.6.6 AS ARM64
# Set environment
ARG BUILD_DEVELOPMENT
# if --build-arg BUILD_DEVELOPMENT=1, set RAILS_ENV to 'development' or set to null otherwise.
ENV RAILS_ENV=${BUILD_DEVELOPMENT:+development}
# if RAILS_ENV is null, set it to 'production' (or leave as is otherwise).
ENV RAILS_ENV=${RAILS_ENV:-production}
# Update and install JS & DB
RUN apt-get update -qq && apt-get install -y nodejs postgresql-client
# Create a directory for the application and use it
RUN mkdir /myapp
WORKDIR /myapp
# Gemfile and lock file need to be present, they'll be overwritten immediately
COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
# Install gem dependencies
RUN gem install bundler:2.2.32
RUN bundle install
RUN curl https://deb.nodesource.com/setup_12.x | bash
ADD https://dl.yarnpkg.com/debian/pubkey.gpg /tmp/yarn-pubkey.gpg
RUN apt-key add /tmp/yarn-pubkey.gpg && rm /tmp/yarn-pubkey.gpg
RUN echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
RUN apt-get update -qq && apt-get install -y yarn && apt-get install -y npm
RUN yarn add bootstrap
COPY . /myapp
# So that webpacker compiles
RUN yarn config set ignore-engines true
RUN rm -rf bin/webpack*
RUN rails webpacker:install
RUN bundle exec rails webpacker:compile
RUN bundle exec rake assets:precompile
# This script runs every time the container is created, necessary for rails
COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
# Run run_dockerfile.sh
COPY run_dockerfile.sh run_dockerfile.sh
RUN chmod u+x run_dockerfile.sh && ./run_dockerfile.sh
##################################################
# Start from the official ruby image
# To run Dockerfile without arm64 architecture
FROM ruby:2.6.6 AS AMD64
# Set environment
ARG BUILD_DEVELOPMENT
# if --build-arg BUILD_DEVELOPMENT=1, set RAILS_ENV to 'development' or set to null otherwise.
ENV RAILS_ENV=${BUILD_DEVELOPMENT:+development}
# if RAILS_ENV is null, set it to 'production' (or leave as is otherwise).
ENV RAILS_ENV=${RAILS_ENV:-production}
# Update and install JS & DB
RUN apt-get update -qq && apt-get install -y nodejs postgresql-client
# Create a directory for the application and use it
RUN mkdir /myapp
WORKDIR /myapp
# Gemfile and lock file need to be present, they'll be overwritten immediately
COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
# Install gem dependencies
RUN gem install bundler:2.2.32
RUN bundle install
RUN curl https://deb.nodesource.com/setup_12.x | bash
ADD https://dl.yarnpkg.com/debian/pubkey.gpg /tmp/yarn-pubkey.gpg
RUN apt-key add /tmp/yarn-pubkey.gpg && rm /tmp/yarn-pubkey.gpg
RUN echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
RUN apt-get update -qq && apt-get install -y yarn && apt-get install -y npm
RUN yarn add bootstrap
COPY . /myapp
# So that webpacker compiles
RUN yarn config set ignore-engines true
RUN rm -rf bin/webpack*
RUN rails webpacker:install
RUN bundle exec rails webpacker:compile
RUN bundle exec rake assets:precompile
# This script runs every time the container is created, necessary for rails
COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
# Run run_dockerfile.sh
COPY run_dockerfile.sh run_dockerfile.sh
RUN chmod u+x run_dockerfile.sh && ./run_dockerfile.sh
Is there any way I could do the .sh or are there any recommendations on the proper way to do it? Thank you!

Answer 1

From the way you've described the problem, you don't really need very many special cases at all.
The one important detail is that it's very easy to override the image's CMD when you run a container. If you have two Compose files, for example, you can just set the service's command:
# docker-compose.yml
version: '3.8'
services:
myapp:
image: registry.example.com/myapp:${MYAPP_TAG:-latest}
ports: ['3000:80']
# docker-compose.override.yml
# for developer use
version: '3.8'
services:
myapp:
build: .
command: rails server -b 0.0.0.0 -p 80
The other variations you list shouldn't matter. You should get consistent results if you build your image FROM --platform=linux/amd64 on an x86-64 host, explicitly specifying the native platform; RUN mkdir a directory you won't use is harmless. The one inconsistency seems to be the container port, but you can explicitly tell rails server which port to use so it matches. I'd use the same image in all environments.
FROM --platform=linux/amd64 ruby:2.6.6 # even on an Intel/AMD host system
...
RUN mkdir tmp/sockets # even if it's unused
CMD ["nginx", "-g", "daemon off;"] # can be overridden when the container runs