In this part, we'll look at our Dockerfile. If you run a > Rails 7.1 version, you can skip this section, as your app comes with a Dockerfile out of the box.
This article is structured into four seperate posts:
This is part 3. If you run a > Rails 7.1 version, you can probably skip this section, as your app comes with a Dockerfile out of the box. Still, it's probably worth familiarising yourself with what's going on here.
Let's shift gears and talk about Docker, a crucial tool for deploying your Rails app. Picture Docker as your app's travel case, packing up all the essentialsācode, libraries, and settingsāso it runs smoothly anywhere, from your laptop to a server. It's about consistency and isolation, ensuring your app behaves the same across all environments and doesn't clash with others when sharing server space.
Now, we'll set up Docker on your machine and pull an image from Docker Hub, which is like a directory of ready-to-go app environments. With Docker, you can effortlessly move your app from development to production, confident it'll run without hiccups.
In our Dockerfile, we're doing a few key things:
If you've started out on a newer Rails version, e.g. 7.1, you should already have a Dockerfile in your root directory of your app. If not, create one and paste the content of this one here but make sure it matches your Ruby version, which you can find in your Gemfile.
# syntax = docker/dockerfile:1
# Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
ARG RUBY_VERSION=3.2.2
FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim as base
# Rails app lives here
WORKDIR /rails
# Set production environment
ENV RAILS_ENV="production" \
BUNDLE_DEPLOYMENT="1" \
BUNDLE_PATH="/usr/local/bundle" \
BUNDLE_WITHOUT="development"
# Throw-away build stage to reduce size of final image
FROM base as build
# Install packages needed to build gems
RUN apt-get update -qq && \
apt-get install --no-install-recommends -y build-essential git libpq-dev libvips pkg-config curl nodejs redis-tools
# Install application gems
COPY Gemfile Gemfile.lock ./
RUN bundle install && \
rm -rf ~/.bundle/ "${BUNDLE_PATH}"/ruby/*/cache "${BUNDLE_PATH}"/ruby/*/bundler/gems/*/.git && \
bundle exec bootsnap precompile --gemfile
# Copy application code
COPY . .
# Precompile bootsnap code for faster boot times
RUN bundle exec bootsnap precompile app/ lib/
# Precompiling assets for production without requiring secret RAILS_MASTER_KEY
RUN SECRET_KEY_BASE_DUMMY=1 ./bin/rails assets:precompile
# Final stage for app image
FROM base
# Install packages needed for deployment
RUN apt-get update -qq && \
apt-get install --no-install-recommends -y curl libvips postgresql-client curl nodejs && \
rm -rf /var/lib/apt/lists /var/cache/apt/archives
# Copy built artifacts: gems, application
COPY --from=build /usr/local/bundle /usr/local/bundle
COPY --from=build /rails /rails
# Run and own only the runtime files as a non-root user for security
RUN useradd rails --create-home --shell /bin/bash && \
chown -R rails:rails db log storage tmp
USER rails:rails
# Entrypoint prepares the database.
ENTRYPOINT ["/rails/bin/docker-entrypoint"]
# Start the server by default, this can be overwritten at runtime
EXPOSE 3000
CMD ["./bin/rails", "server"]
This adds a few libraries, e.g. nodejs, I found I needed to make it work.
Also this is the setup for compiling your Javascrip with importmaps. If you're using e.g. esbuild, your Dockerfile needs to account for that by adding yarn. This one worked for me:
# syntax = docker/dockerfile:1
# Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
ARG RUBY_VERSION=3.2.2
FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim as base
# Rails app lives here
WORKDIR /rails
# Set production environment
ENV RAILS_ENV="production" \
BUNDLE_DEPLOYMENT="1" \
BUNDLE_PATH="/usr/local/bundle" \
BUNDLE_WITHOUT="development"
# Throw-away build stage to reduce size of final image
FROM base as build
# Install packages needed to build gems
RUN apt-get update -qq && \
apt-get install --no-install-recommends -y build-essential curl default-libmysqlclient-dev git libpq-dev libvips pkg-config node-gyp pkg-config python-is-python3 nodejs redis-tools
# Install JavaScript dependencies
ARG NODE_VERSION=19.7.0
ARG YARN_VERSION=1.22.19
ENV PATH=/usr/local/node/bin:$PATH
RUN curl -sL https://github.com/nodenv/node-build/archive/master.tar.gz | tar xz -C /tmp/ && \
/tmp/node-build-master/bin/node-build "${NODE_VERSION}" /usr/local/node && \
npm install -g yarn@$YARN_VERSION && \
rm -rf /tmp/node-build-master
# Install application gems
COPY Gemfile Gemfile.lock ./
RUN bundle install && \
rm -rf ~/.bundle/ "${BUNDLE_PATH}"/ruby/*/cache "${BUNDLE_PATH}"/ruby/*/bundler/gems/*/.git && \
bundle exec bootsnap precompile --gemfile
# Install node modules
COPY --link package.json yarn.lock ./
RUN yarn install --frozen-lockfile
# Copy application code
COPY . .
# Precompile bootsnap code for faster boot times
RUN bundle exec bootsnap precompile app/ lib/
# Precompiling assets for production without requiring secret RAILS_MASTER_KEY
RUN SECRET_KEY_BASE_DUMMY=1 ./bin/rails assets:precompile --trace
# Final stage for app image
FROM base
# Install packages needed for deployment
RUN apt-get update -qq && \
apt-get install --no-install-recommends -y curl libvips postgresql-client nodejs && \
rm -rf /var/lib/apt/lists /var/cache/apt/archives
# Copy built artifacts: gems, application
COPY --from=build /usr/local/bundle /usr/local/bundle
COPY --from=build /rails /rails
# Run and own only the runtime files as a non-root user for security
RUN useradd rails --create-home --shell /bin/bash && \
chown -R rails:rails db log storage tmp
USER rails:rails
# Entrypoint prepares the database.
ENTRYPOINT ["/rails/bin/docker-entrypoint"]
# Start the server by default, this can be overwritten at runtime
EXPOSE 3000
CMD ["./bin/rails", "server"]
That's really it for Docker, let's explore the remaining steps to actually deploy our app and see what we need to do to add more apps after the first one. Go to part 4