#cloud-config
# This cloud-init configuration defines systemd services to run Docker containers
# on Container-Optimized OS (COS) with full observability support.

write_files:
%{ for name, container in containers ~}
  - path: /etc/systemd/system/${name}.service
    permissions: 0644
    owner: root
    content: |
      [Unit]
      Description=Containerized application: ${name}
      # Wait for the Docker socket to be ready
      Wants=docker.socket
      After=docker.service
      
      [Service]
      # Crucial for persistence: ensure the service restarts on exit.
      Restart=${container.restart_policy}
      RestartSec=5s

      # Set HOME to writable location for docker credential helper
      Environment="HOME=/home/cloudservice"
      Environment="DOCKER_CONFIG=/home/cloudservice/.docker"

      # Stop and remove any pre-existing container with the same name.
      # The minus sign prefix means failure is tolerated
      ExecStartPre=-/usr/bin/docker stop ${name}
      ExecStartPre=-/usr/bin/docker rm ${name}

      # Configure docker credential helper for Artifact Registry
      ExecStartPre=/usr/bin/docker-credential-gcr configure-docker --registries=${region}-docker.pkg.dev

      # Pull the image before starting.
      ExecStartPre=/usr/bin/docker pull ${container.image}
      
      # The main execution command: docker run.
      # When logging is enabled, use the gcplogs driver to send container logs to Cloud Logging.
      ExecStart=/usr/bin/docker run \
        --name ${name} \
%{ if enable_logging ~}
        --log-driver=gcplogs \
        --log-opt gcp-project=${project_id} \
        --log-opt gcp-log-cmd=true \
        --log-opt gcp-meta-zone=true \
        --log-opt gcp-meta-name=true \
        --log-opt labels=container_name \
        --label container_name=${name} \
%{ endif ~}
%{ for port in container.ports ~}
        -p ${port} \
%{ endfor ~}
%{ for e in container.env ~}
        -e ${e.name}="${e.value}" \
%{ endfor ~}
        ${container.image} \
%{ if container.command != "" ~}
        "${container.command}" \
%{ endif ~}
%{ for arg in container.args ~}
        # Escape single quotes: end quoted string, add escaped quote, resume quoted string
        '${replace(arg, "'", "'\\''")}' \
%{ endfor ~}

      
      # ExecStop is called when the service is stopped manually.
      ExecStop=/usr/bin/docker stop ${name}

      [Install]
      WantedBy=multi-user.target

%{ endfor ~}

runcmd:
  # Configure docker-credential-gcr for Artifact Registry authentication
  - docker-credential-gcr configure-docker
  # Reload the systemd configuration to recognize the new service files.
  - systemctl daemon-reload
%{ for name, container in containers ~}
  # Enable and start ${name} service.
  - systemctl enable ${name}.service
  - systemctl start ${name}.service
%{ endfor ~}