A Simple Analogy

Docker Compose is like a conductor orchestrating an orchestra. Each instrument (container) plays its part in harmony.

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Why Docker Compose?

• Multi-container: Manage multiple services
• Development: Easy local environment
• Networking: Built-in service discovery
• Volumes: Persistent data management
• Scaling: Scale services easily

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Full Example

version: '3.9'

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgresql://user:pass@db:5432/myapp
    depends_on:
      - db
      - redis
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      timeout: 10s
      retries: 3

  db:
    image: postgres:15-alpine
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: myapp
    volumes:
      - db_data:/var/lib/postgresql/data
    ports:
      - "5432:5432"

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    volumes:
      - redis_data:/data

volumes:
  db_data:
  redis_data:

networks:
  default:
    name: myapp-network

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Build Configuration

web:
  build:
    context: .
    dockerfile: Dockerfile
    args:
      BUILD_DATE: 2025-02-20
      VERSION: 1.0
    target: production
  image: myapp:latest

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Advanced Networking

services:
  frontend:
    networks:
      - frontend
  
  backend:
    networks:
      - backend
  
  db:
    networks:
      - backend

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

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Commands

# Build images
docker compose build

# Start services
docker compose up -d

# View logs
docker compose logs -f web

# Scale service
docker compose up -d --scale worker=3

# Stop services
docker compose down

# Remove volumes
docker compose down -v

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Best Practices

1. Health checks: Define startup verification
2. Dependencies: Use depends_on for ordering
3. Networking: Use service names for communication
4. Volumes: Separate data from code
5. Environment: Use .env files for secrets

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Related Concepts

• Docker Swarm
• Kubernetes
• Container orchestration
• Microservices

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Summary

Docker Compose simplifies multi-container development. Use services, networking, volumes, and health checks for production-ready setups.