Dockerfile

# syntax = docker/dockerfile:1

# Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
ARG RUBY_VERSION=3.2.0
FROM ruby:$RUBY_VERSION-slim as base

# Rails app lives here
WORKDIR /rails

# Set production environment
ENV RAILS_ENV="production" \
    BUNDLE_PATH="vendor/bundle" \
    BUNDLE_WITHOUT="development:test"

# Update gems and preinstall the desired version of bundler
ARG BUNDLER_VERSION=2.4.5
RUN gem update --system --no-document && \
    gem install -N bundler -v ${BUNDLER_VERSION}


# 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 libpq-dev

# Install application gems
COPY Gemfile Gemfile.lock ./
RUN bundle _${BUNDLER_VERSION}_ install && \
    bundle exec bootsnap precompile --gemfile

# Copy application code
COPY . .

# Precompile bootsnap code for faster boot times
RUN bundle exec bootsnap precompile app/ lib/


# Final stage for app image
FROM base

# Install packages needed for deployment
RUN apt-get update -qq && \
    apt-get install --no-install-recommends -y postgresql-client && \
    rm -rf /var/lib/apt/lists /var/cache/apt/archives

# Copy built application from previous stage
COPY --from=build /rails /rails

# Deployment options
ENV RAILS_LOG_TO_STDOUT="1" \
    RAILS_SERVE_STATIC_FILES="true"

# 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"]