Docker Compositor

Overview

This role deploys and manages Docker Compose stacks with intelligent change detection, database initialization, and monitoring integration. It creates the necessary directory structure, generates docker-compose.yml from templates, implements idempotency checks to prevent unnecessary restarts, schedules Centreon monitoring downtimes during updates, and handles database initialization for PostgreSQL and MariaDB/MySQL containers. This role also creates a .env file for every service that needs it, securing sensitive data.

What This Role Does

Step 1: Prerequisites

1. Creates compose directory (e.g., /home/user/docker/compose/)
2. Creates volume directories for all services with proper ownership
3. Creates Glance config directory (if Glance service present)
4. Copies Glance configuration files (glance.yml, home.yml)
5. Creates .env files for services with sensitive variables (mode 0600)

Step 2: Idempotency Check

1. Checks if current compose file exists
2. Generates temporary compose file from template
3. Calculates SHA256 checksums for both files
4. Compares checksums to detect changes
5. Deletes temporary file
6. If changes detected:
   • Calculate downtime window (start time + duration)
   • Schedule Centreon downtime for “Docker Containers Uptime” service
   • Stop all containers cleanly

Step 3: Installation/Update

1. Deploys docker-compose.yml from template
2. Starts database containers first (postgresql, mariadb)
3. Waits 15 seconds for databases to initialize
4. Initializes PostgreSQL databases:
   • Check if user exists (idempotent)
   • Create user if needed
   • Check if database exists (idempotent)
   • Create database if needed with correct owner
5. Initializes MariaDB/MySQL databases:
   • Create database if not exists
   • Create user if not exists
   • Grant privileges
   • Flush privileges
6. Starts all services with Docker Compose V2:
   • Project name: docker_compose_stack_name
   • Remove orphans: true (cleanup old services)
   • Recreate: auto (only if changed)
   • Pull: missing (pull images if not present)
   • Dependencies: true (respect depends_on)
   • Wait: true (wait for health checks)
   • Wait timeout: 600 seconds (10 minutes)

Role Variables

Variable	Description
docker_compose_directory	Directory containing docker-compose.yml (from host_vars)
docker_data_path	Base path for container data volumes (from host_vars)
docker_user	User that owns Docker files and volumes (from host_vars)
docker_compose_file	Compose file name (from host_vars)
docker_compose_stack_name	Docker Compose project name (from host_vars)
docker_compositor_definition	Complete stack definition (from host_vars)
docker_compositor_postgres_databases	PostgreSQL databases to create on first run
docker_compositor_mysql_databases	MariaDB/MySQL databases to create on first run
docker_compositor_downtime_duration_minutes	Centreon downtime duration during updates

Stack definition structure:

docker_compositor_definition:
  state: present  # present, stopped, or absent

  services:
    - name: service_name
      image: docker/image:tag
      container_name: container_name
      restart_policy: unless-stopped
      volumes:
        - folder_path_on_host: "{{ docker_data_path }}/app/data"
          folder_path_in_container: /data
          owner: "{{ docker_user }}"
          group: "{{ docker_user }}"
          mode: '0755'
      environment:
        PUBLIC_VAR: "value"
      sensitive_env_vars:
        SECRET_KEY: "{{ vault_secret }}"
      ports:
        - "8080:80"
      networks:
        - app_network

Notes

• Containers are only restarted when the compose file actually changes (idempotent)
• Sensitive environment variables are stored in .env files, not in compose file
• Database initialization runs only on first deploy (when containers are new)
• Role schedules a Centreon downtime before restarting containers