docker-compose-setup

# Docker Compose Setup

This skill enables the agent to design and configure multi-container application stacks using Docker Compose. The agent can orchestrate services including web servers, databases, caches, background workers, and reverse proxies with proper networking, volume management, health checks, and environment-specific overrides. The agent understands both development and production configurations and can generate compose files that follow Docker best practices.

## Workflow

1. **Analyze the Application Stack:** The agent reviews the project's architecture to identify all required services and their dependencies. This includes the primary application container, databases (PostgreSQL, MySQL, MongoDB), caches (Redis, Memcached), message queues (RabbitMQ, Kafka), background workers, and reverse proxies (Nginx, Traefik). The agent maps inter-service dependencies to determine startup order and health check requirements.

2. **Define Services and Images:** For each service, the agent specifies the Docker image or build context, exposed ports, environment variables, and resource constraints. Application services typically use a `build` directive pointing to a local Dockerfile, while infrastructure services use official images with pinned version tags. The agent avoids using `latest` tags in production to ensure reproducible deployments.

3. **Configure Networking and Service Discovery:** The agent creates named Docker networks to isolate traffic between service tiers (e.g., a `frontend` network for the proxy and app, a `backend` network for the app and database). Services communicate using their compose service names as DNS hostnames, eliminating the need for hardcoded IP addresses.

4. **Set Up Volumes and Persistence:** The agent defines named volumes for data that must persist across container restarts, such as database storage and file uploads. For development, bind mounts map the host source code into containers to enable hot reloading. The agent ensures that volume permissions and ownership are configured correctly for the container's runtime user.

5. **Add Health Checks and Dependency Ordering:** The agent configures health checks for critical services so that dependent services wait until their dependencies are truly ready, not just started. This prevents common issues like an application container crashing because the database has started but is not yet accepting connections. The `depends_on` directive with `condition: service_healthy` enforces correct startup order.

6. **Create Environment-Specific Overrides:** The agent generates a base `docker-compose.yml` for shared configuration and an override file (`docker-compose.override.yml` for development, `docker-compose.prod.yml` for production) to customize settings per environment. Development overrides include bind mounts, debug ports, and verbose logging, while production overrides include resource limits, restart policies, and optimized logging drivers.

## Supported Technologies

- **Compose Versions:** Docker Compose V2 (integrated Docker CLI plugin)
- **Application Runtimes:** Node.js, Python, Ruby, Go, Java, PHP, .NET
- **Databases:** PostgreSQL, MySQL, MariaDB, MongoDB, Redis, Elasticsearch
- **Reverse Proxies:** Nginx, Traefik, Caddy, HAProxy
- **Message Queues:** RabbitMQ, Kafka, NATS
- **Monitoring:** Prometheus, Grafana, cAdvisor

## Usage

Provide the agent with a description of your application stack, including the services needed, their relationships, and whether the setup is for development or production.

**Example prompt:**

```
Create a docker-compose setup for my Node.js app with:
- PostgreSQL database with persistent storage
- Redis for session caching
- Nginx reverse proxy with SSL termination
- A Celery-like background worker process
- Development setup with hot reloading
```

## Examples

### Example 1: Full Stack Web Application (Node.js + PostgreSQL + Redis + Nginx)

```yaml
services:
  nginx:
    image: nginx:1.25-alpine
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
      - ./nginx/certs:/etc/nginx/certs:ro
    depends_on:
      app:
        condition: service_healthy
    networks:
      - frontend
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost/health"]
      interval: 30s
      timeout: 5s
      retries: 3

  app:
    build:
      context: .
      dockerfile: Dockerfile
    environment:
      NODE_ENV: production
      DATABASE_URL: postgres://appuser:${DB_PASSWORD}@postgres:5432/myapp
      REDIS_URL: redis://redis:6379
      SESSION_SECRET: ${SESSION_SECRET}
    depends_on:
      postgres:
        condition: service_healthy
      redis:
        condition: service_healthy
    networks:
      - frontend
      - backend
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "node", "-e", "fetch('http://localhost:3000/health').then(r => r.ok ? process.exit(0) : process.exit(1))"]
      interval: 15s
      timeout: 5s
      retries: 3
      start_period: 30s

  worker:
    build:
      context: .
      dockerfile: Dockerfile
    command: node worker.js
    environment:
      DATABASE_URL: postgres://appuser:${DB_PASSWORD}@postgres:5432/myapp
      REDIS_URL: redis://redis:6379
    depends_on:
      postgres:
        condition: service_healthy
      redis:
        condition: service_healthy
    networks:
      - backend
    restart: unless-stopped

  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: myapp
      POSTGRES_USER: appuser
      POSTGRES_PASSWORD: ${DB_PASSWORD}
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql:ro
    networks:
      - backend
    restart: unless-stopped
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U appuser -d myapp"]
      interval: 10s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7-alpine
    command: redis-server --appendonly