Dockerfile.dev

# syntax=docker/dockerfile:1

# Development image. The production image is the default Dockerfile; see docs/DOCKER.md.
#
#   docker compose build
#   docker compose up -d
#
# Unlike the production image this one keeps the development and test gems and
# skips asset precompilation, so the Tailwind watcher can rebuild CSS on the fly.
# compose.yaml bind-mounts the working tree over /rails, so rebuilds are only
# needed after Gemfile or config/boot changes.

# Make sure RUBY_VERSION matches the Ruby version in .ruby-version
ARG RUBY_VERSION=3.4.4
FROM docker.io/library/ruby:$RUBY_VERSION-slim

# Rails app lives here
WORKDIR /rails

# Runtime packages plus the toolchain needed to compile native gems. The
# toolchain is dropped in the same layer to keep the image a single stage.
# ffmpeg backs the audio pipeline, and ImageMagick with libheif backs the HEIC
# to JPEG conversion in Image::ConvertHeicToJpegJob, which mini_magick shells out
# to for the "convert" binary.
RUN apt-get update -qq && \
    apt-get install --no-install-recommends -y \
      build-essential \
      curl \
      ffmpeg \
      git \
      imagemagick \
      libheif-examples \
      libjemalloc2 \
      libpq-dev \
      libvips \
      libyaml-dev \
      pkg-config \
      postgresql-client && \
    ln -s /usr/lib/$(uname -m)-linux-gnu/libjemalloc.so.2 /usr/local/lib/libjemalloc.so && \
    rm -rf /var/lib/apt/lists /var/cache/apt/archives

# Development environment with the full bundle installed.
# RAILS_ENV is deliberately left unset: Rails then defaults to development for
# bin/rails, while the test suite can still set RAILS_ENV=test through the ||= in
# spec/rails_helper.rb. Baking in "development" would run the specs against the
# development database.
# BUNDLE_PATH stays outside /rails so the bind mount never shadows the gems.
ENV BUNDLE_PATH="/usr/local/bundle" \
    LD_PRELOAD="/usr/local/lib/libjemalloc.so"

COPY vendor/* ./vendor/
COPY Gemfile Gemfile.lock ./

# -j 1 disable parallel compilation to avoid a QEMU bug: https://github.com/rails/bootsnap/issues/495
RUN bundle install -j 1

# Application code. Shadowed by the bind mount at runtime, but it keeps the image
# usable on its own and caches the bootsnap gem index.
COPY . .

# Run and own only the runtime files as a non-root user for security.
# The uid is 1000 to match the default host user, so bind-mounted files stay writable.
RUN groupadd --system --gid 1000 rails && \
    useradd rails --uid 1000 --gid 1000 --create-home --shell /bin/bash
USER 1000:1000

# Entrypoint prepares the database when the server is the process being run.
ENTRYPOINT ["/rails/bin/docker-entrypoint"]

# BINDING must be set to 0.0.0.0 (see compose.yaml): in development Rails binds
# to localhost only, which is unreachable from outside the container.
CMD ["./bin/rails", "server"]