RFC: Improved launch/Dockerfile for Rails applications

1

Current user experience:

Your Rails app is prepared for deployment. Production will be set up with these versions of core runtime packages:

Ruby 3.1.2
Bundler 2.3.15
NodeJS 18.4.0

You can configure these in the [build] section in the generated fly.toml.

Ruby versions available are: 3.1.2, 3.0.4, and 2.7.6. Learn more about the chosen Ruby stack, Fullstaq Ruby, here: https://github.com/evilmartians/fullstaq-ruby-docker.
We recommend using the highest patch level for better security and performance.

For the other packages, specify any version you need.

If you need custom packages installed, or have problems with your deployment build, you may need to edit the Dockerfile
for app-specific changes. If you need help, please post on https://community.fly.io.

Now: run 'fly deploy' to deploy your Rails app.

I’d like to make this a bit less intimidating:

Your Rails app is prepared for deployment.

If you need custom packages installed, or have problems with your deployment
build, you may need to edit the Dockerfile for app-specific changes. If you
need help, please post on https://community.fly.io.

Now: run 'fly deploy' to deploy your Rails app.

Now onto the Dockerfile itself. Current output:

# syntax = docker/dockerfile:experimental
ARG RUBY_VERSION=2.7.3
ARG VARIANT=jemalloc-slim
FROM quay.io/evl.ms/fullstaq-ruby:${RUBY_VERSION}-${VARIANT} as base

ARG NODE_VERSION=16
ARG BUNDLER_VERSION=2.3.9

ARG RAILS_ENV=production
ENV RAILS_ENV=${RAILS_ENV}

ENV RAILS_SERVE_STATIC_FILES true
ENV RAILS_LOG_TO_STDOUT true

ARG BUNDLE_WITHOUT=development:test
ARG BUNDLE_PATH=vendor/bundle
ENV BUNDLE_PATH ${BUNDLE_PATH}
ENV BUNDLE_WITHOUT ${BUNDLE_WITHOUT}

RUN mkdir /app
WORKDIR /app
RUN mkdir -p tmp/pids

SHELL ["/bin/bash", "-c"]

RUN curl https://get.volta.sh | bash

ENV BASH_ENV ~/.bashrc
ENV VOLTA_HOME /root/.volta
ENV PATH $VOLTA_HOME/bin:/usr/local/bin:$PATH

RUN volta install node@${NODE_VERSION} && volta install yarn

FROM base as build_deps

ARG DEV_PACKAGES="git build-essential libpq-dev wget vim curl gzip xz-utils libsqlite3-dev"
ENV DEV_PACKAGES ${DEV_PACKAGES}

RUN --mount=type=cache,id=dev-apt-cache,sharing=locked,target=/var/cache/apt \
    --mount=type=cache,id=dev-apt-lib,sharing=locked,target=/var/lib/apt \
    apt-get update -qq && \
    apt-get install --no-install-recommends -y ${DEV_PACKAGES} \
    && rm -rf /var/lib/apt/lists /var/cache/apt/archives

FROM build_deps as gems

RUN gem install -N bundler -v ${BUNDLER_VERSION}

COPY Gemfile* ./
RUN bundle install &&  rm -rf vendor/bundle/ruby/*/cache

FROM build_deps as node_modules

COPY package*json ./
COPY yarn.* ./

RUN if [ -f "yarn.lock" ]; then \
    yarn install; \
    elif [ -f "package-lock.json" ]; then \
    npm install; \
    else \
    mkdir node_modules; \
    fi

FROM base

ARG PROD_PACKAGES="postgresql-client file vim curl gzip libsqlite3-0"
ENV PROD_PACKAGES=${PROD_PACKAGES}

RUN --mount=type=cache,id=prod-apt-cache,sharing=locked,target=/var/cache/apt \
    --mount=type=cache,id=prod-apt-lib,sharing=locked,target=/var/lib/apt \
    apt-get update -qq && \
    apt-get install --no-install-recommends -y \
    ${PROD_PACKAGES} \
    && rm -rf /var/lib/apt/lists /var/cache/apt/archives

COPY --from=gems /app /app
COPY --from=node_modules /app/node_modules /app/node_modules

ENV SECRET_KEY_BASE 1

COPY . .

RUN chmod +x /app/bin/* && \
    sed -i 's/ruby.exe/ruby/' /app/bin/* && \
    sed -i '/^#!/aDir.chdir File.expand_path("..", __dir__)' /app/bin/*

RUN bin/rails fly:build

ENV PORT 8080

ARG SERVER_COMMAND="bin/rails fly:server"
ENV SERVER_COMMAND ${SERVER_COMMAND}
CMD ${SERVER_COMMAND}

Issues I’d like to address:

  • No comments
  • Oddly specific version numbers that don’t match what you would expect (they are overriden by fly.toml)
  • Installation of things that aren’t necessarily needed (volta, node, yarn)
  • If statements in Dockerfile when the conditions can be predetermined
  • Multi-state build steps are called “dev” and “prod” instead of “build” and “deploy”

Proposed new Dockerfile, in this case for an import maps application (i.e., no node, yarn)

# syntax = docker/dockerfile:experimental

# Dockerfile used to build a deployable image for a Rails application.
# Adjust as required.
#
# Common adjustments you may need to make over time:
#  * Modify version numbers for Ruby, Bundler, and other products.
#  * Add library packages needed at build time for your gems, node modules.
#  * Add deployment packages needed by your application
#  * Add (often fake) secrets needed to compile your assets

#######################################################################

# Learn more about the chosen Ruby stack, Fullstaq Ruby, here:
#   https://github.com/evilmartians/fullstaq-ruby-docker.
#
# We recommend using the highest patch level for better security and
# performance.

ARG RUBY_VERSION=3.1.2
ARG VARIANT=jemalloc-slim
FROM quay.io/evl.ms/fullstaq-ruby:${RUBY_VERSION}-${VARIANT} as base

ARG BUNDLER_VERSION=2.3.15

ARG RAILS_ENV=production
ENV RAILS_ENV=${RAILS_ENV}

ENV RAILS_SERVE_STATIC_FILES true
ENV RAILS_LOG_TO_STDOUT true

ARG BUNDLE_WITHOUT=development:test
ARG BUNDLE_PATH=vendor/bundle
ENV BUNDLE_PATH ${BUNDLE_PATH}
ENV BUNDLE_WITHOUT ${BUNDLE_WITHOUT}

RUN mkdir /app
WORKDIR /app
RUN mkdir -p tmp/pids

#######################################################################

# install packages only needed at build time

FROM base as build_deps

ARG BUILD_PACKAGES="git build-essential libpq-dev wget vim curl gzip xz-utils libsqlite3-dev"
ENV BUILD_PACKAGES ${BUILD_PACKAGES}

RUN --mount=type=cache,id=dev-apt-cache,sharing=locked,target=/var/cache/apt \
    --mount=type=cache,id=dev-apt-lib,sharing=locked,target=/var/lib/apt \
    apt-get update -qq && \
    apt-get install --no-install-recommends -y ${BUILD_PACKAGES} \
    && rm -rf /var/lib/apt/lists /var/cache/apt/archives

#######################################################################

# install gems

FROM build_deps as gems

RUN gem update --system --no-document && \
    gem install -N bundler -v ${BUNDLER_VERSION}

COPY Gemfile* ./
RUN bundle install &&  rm -rf vendor/bundle/ruby/*/cache

#######################################################################

# install deployment packages

FROM base

ARG DEPLOY_PACKAGES="postgresql-client file vim curl gzip libsqlite3-0"
ENV DEPLOY_PACKAGES=${DEPLOY_PACKAGES}

RUN --mount=type=cache,id=prod-apt-cache,sharing=locked,target=/var/cache/apt \
    --mount=type=cache,id=prod-apt-lib,sharing=locked,target=/var/lib/apt \
    apt-get update -qq && \
    apt-get install --no-install-recommends -y \
    ${DEPLOY_PACKAGES} \
    && rm -rf /var/lib/apt/lists /var/cache/apt/archives

# copy installed gems
COPY --from=gems /app /app
COPY --from=gems /usr/lib/fullstaq-ruby/versions /usr/lib/fullstaq-ruby/versions
COPY --from=gems /usr/local/bundle /usr/local/bundle

#######################################################################

# Deploy your application
COPY . .

# Adjust binstubs to run on Linux and set current working directory
RUN chmod +x /app/bin/* && \
    sed -i 's/ruby.exe/ruby/' /app/bin/* && \
    sed -i '/^#!/aDir.chdir File.expand_path("..", __dir__)' /app/bin/*

# The following enable assets to precompile on the build server.  Adjust
# as necessary.  If no combination works for you, see:
# https://fly.io/docs/rails/getting-started/existing/#access-to-environment-variables-at-build-time
ENV SECRET_KEY_BASE 1
# ENV AWS_ACCESS_KEY_ID=1
# ENV AWS_SECRET_ACCESS_KEY=1

# Run build task defined in lib/tasks/fly.rake
ARG BUILD_COMMAND="bin/rails fly:build"
RUN ${BUILD_COMMAND}

# Default server start instructions.  Generally Overridden by fly.toml.
ENV PORT 8080
ARG SERVER_COMMAND="bin/rails fly:server"
ENV SERVER_COMMAND ${SERVER_COMMAND}
CMD ${SERVER_COMMAND}
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