compose-guide.md

Docker Compose Guide

Docker Compose is a tool for defining and running multi-container Docker applications.

Basic docker-compose.yml Structure

version: '3.8'

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
    depends_on:
      - db
      - redis

  db:
    image: postgres:13
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      - POSTGRES_USER=myapp
      - POSTGRES_PASSWORD=secret
      - POSTGRES_DB=myapp

  redis:
    image: redis:6-alpine
    volumes:
      - redis_data:/data

volumes:
  postgres_data:
  redis_data:

networks:
  backend:
    driver: bridge

Common Configurations

Building Images

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
      args:
        - NODE_ENV=production

Environment Variables

services:
  web:
    env_file:
      - .env
    environment:
      - API_KEY=secret
      - DEBUG=0

Volumes

services:
  db:
    volumes:
      # Named volume
      - db_data:/var/lib/mysql
      # Bind mount
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql
      # Anonymous volume
      - /var/lib/mysql

volumes:
  db_data:
    driver: local

Networks

services:
  web:
    networks:
      - frontend
      - backend

  db:
    networks:
      - backend

networks:
  frontend:
    driver: bridge
  backend:
    driver: bridge

Dependencies

services:
  web:
    depends_on:
      db:
        condition: service_healthy
      redis:
        condition: service_started

Healthchecks

services:
  web:
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 40s

Example Configurations

Web Application Stack

version: '3.8'

services:
  nginx:
    image: nginx:alpine
    ports:
      - "80:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
    depends_on:
      - web

  web:
    build: .
    expose:
      - "3000"
    environment:
      - NODE_ENV=production
      - DB_HOST=db
    depends_on:
      - db
      - redis

  db:
    image: postgres:13
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      - POSTGRES_USER=${DB_USER}
      - POSTGRES_PASSWORD=${DB_PASSWORD}

  redis:
    image: redis:6-alpine
    volumes:
      - redis_data:/data

volumes:
  postgres_data:
  redis_data:

Development Environment

version: '3.8'

services:
  web:
    build:
      context: .
      target: development
    volumes:
      - .:/app
      - /app/node_modules
    command: npm run dev
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=development

Common Commands

# Start services
docker-compose up

# Start in detached mode
docker-compose up -d

# Build/rebuild services
docker-compose build

# Stop services
docker-compose down

# Stop and remove volumes
docker-compose down -v

# View logs
docker-compose logs -f

# Execute command in container
docker-compose exec web npm run test

# List containers
docker-compose ps

# Show resource usage
docker-compose top

Best Practices

1. Version Control

• Use specific versions for images
• Pin dependencies in Dockerfile
• Use environment variables for configuration

2. Security

• Don't commit sensitive data
• Use environment files
• Set appropriate file permissions

3. Development vs Production

• Use different compose files
• Override with docker-compose.override.yml
• Use build targets for different environments

4. Resource Management

• Set memory and CPU limits
• Use health checks
• Configure logging appropriately

5. Networking

• Use internal networks when possible
• Limit exposed ports
• Use network aliases

6. Volumes

• Use named volumes for persistence
• Use bind mounts for development
• Clean up unused volumes