feat(docker): support custom plugins and dependencies in centreon-engine container

[Tpo76]

MON-201883

Adds two mechanisms to let users extend the centreon-engine container with their own plugins and dependencies, without modifying the base image.

Changes

Custom scripts — volume mount point

A dedicated directory /usr/lib/nagios/plugins/custom/ is created and owned by centreon-engine in the Dockerfile. Users mount their scripts there via docker-compose:

volumes:
  - ./my-plugins:/usr/lib/nagios/plugins/custom:ro

Scripts must be executable (chmod +x).

Runtime APT dependencies — custom-deps.json

New entrypoint script 41-custom-deps.sh (runs after 40-engine.sh) reads /etc/centreon-engine/custom-deps.json at startup and installs the listed APT packages:

{
  "apt": ["snmp", "python3-requests", "libnet-snmp-perl"]
}

Package names are validated against Debian naming rules in check_custom_deps.py before being passed to apt-get.

Hot-reload is handled by 46-custom-deps-watcher_background.sh: same inotify pattern as the existing 45-plugin-watcher_background.sh, re-installs whenever custom-deps.json changes.

Mount in docker-compose:

volumes:
  - ./custom-deps.json:/etc/centreon-engine/custom-deps.json:ro

No sudoers changes required — apt/apt-get are already allowed.

Custom image build

For pip3/cpan/compiled dependencies, users extend the published image:

FROM centreon/centreon-engine:24.10
USER root
RUN apt-get update && apt-get install -y --no-install-recommends \
    python3-boto3 libnet-snmp-perl && \
    rm -rf /var/lib/apt/lists/*
USER centreon-engine

Test plan

• Build with existing .deb mount → unchanged behaviour
• Mount a script directory → verify centreon-engine can call /usr/lib/nagios/plugins/custom/my-script.sh
• Mount custom-deps.json with "apt": ["snmp"] → dpkg -l snmp shows installed after startup
• Modify custom-deps.json while container is running → package installs without restart
• Invalid package name in custom-deps.json → skipped with warning, valid packages still installed

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch MON-201883-feat-docker-support-custom-plugins-and-dependencies-in-centreon-engine-container

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