Use pre-built Docker images in CI to reduce setup time

[bburda]

Summary

CI spends ~3 minutes per job on setup-ros and apt-get install to install ROS 2 and project dependencies. With 4+ parallel jobs (Jazzy build, Jazzy lint, Jazzy test, Humble, Rolling, coverage), this adds up to ~18 minutes of total compute time on redundant setup.

Pre-building Docker images with ROS 2 and project dependencies pre-installed would eliminate this overhead.

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Proposed solution (optional)

Build and publish Docker images to GHCR with ROS 2 + all project deps:

# Example for Jazzy
FROM ros:jazzy
RUN apt-get update && apt-get install -y \
  ccache clang-format clang-tidy lcov \
  ros-jazzy-test-msgs \
  && rm -rf /var/lib/apt/lists/*
COPY src /tmp/src
RUN . /opt/ros/jazzy/setup.sh \
  && rosdep update \
  && rosdep install --from-paths /tmp/src --ignore-src -y \
  && rm -rf /tmp/src

A separate workflow would rebuild images weekly or on dependency changes, publishing to ghcr.io/selfpatch/ros2_medkit-ci:jazzy / :humble.

CI jobs would then use:

container:
  image: ghcr.io/selfpatch/ros2_medkit-ci:${{ matrix.ros_distro }}

Expected savings: ~3-4 min per job, ~18 min total compute across all jobs.

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Additional context (optional)

Current CI timing breakdown (Jazzy job):

• Setup ROS 2: ~3 min
• Install dependencies: ~30s
• Build: ~5 min (1.5 min with warm ccache)
• Linters: ~20 min
• Tests: ~3 min