docker-compose

# Docker Compose — Multi-Container Orchestration Manage multi-container Docker applications with docker-compose. Define services, networks, volumes, and dependencies in YAML. Perfect for local development, testing, and simple production deployments. ## When to Use - Setting up local development environments - Running multi-service applications (app + database + cache) - Testing microservices locally - CI/CD pipeline containers - Simple production deployments ## Core Concepts ### Services ```yaml services: app: build: . ports: - "3000:3000" depends_on: - db db: image: postgres:15 environment: POSTGRES_PASSWORD: secret volumes: - db-data:/var/lib/postgresql/data volumes: db-data: ``` ### Networks ```yaml networks: frontend: backend: services: app: networks: - frontend - backend db: networks: - backend ``` ## Common Patterns ### 1. Full-Stack App (Frontend + Backend + Database) ```yaml version: '3.8' services: frontend: build: ./frontend ports: - "3000:3000" environment: - REACT_APP_API_URL=http://localhost:8000 depends_on: - backend backend: build: ./backend ports: - "8000:8000" environment: - DATABASE_URL=postgresql://user:pass@db:5432/myapp depends_on: - db db: image: postgres:15 environment: - POSTGRES_USER=user - POSTGRES_PASSWORD=pass - POSTGRES_DB=myapp volumes: - postgres-data:/var/lib/postgresql/data volumes: postgres-data: ``` ### 2. Microservices with Redis Cache ```yaml services: api: build: ./api ports: - "8000:8000" environment: - REDIS_URL=redis://cache:6379 depends_on: - cache - db worker: build: ./worker environment: - REDIS_URL=redis://cache:6379 depends_on: - cache cache: image: redis:7-alpine ports: - "6379:6379" db: image: postgres:15 environment: - POSTGRES_PASSWORD=secret volumes: - db-data:/var/lib/postgresql/data volumes: db-data: ``` ### 3. Development with Hot Reload ```yaml services: app: build: context: . target: development volumes: - .:/app - /app/node_modules ports: - "3000:3000" environment: - NODE_ENV=development command: npm run dev ``` ## Essential Commands ```bash # Start all services docker-compose up # Start in background docker-compose up -d # Build and start docker-compose up --build # Stop all services docker-compose down # Stop and remove volumes docker-compose down -v # View logs docker-compose logs -f # View logs for specific service docker-compose logs -f app # Execute command in service docker-compose exec app sh # Scale service docker-compose up -d --scale worker=3 # Restart service docker-compose restart app # View running services docker-compose ps ``` ## Best Practices ### 1. Use .env Files ```bash # .env POSTGRES_PASSWORD=secret API_PORT=8000 ``` ```yaml # docker-compose.yml services: db: environment: - POSTGRES_PASSWORD=${POSTGRES_PASSWORD} api: ports: - "${API_PORT}:8000" ``` ### 2. Health Checks ```yaml services: app: healthcheck: test: ["CMD", "curl", "-f", "http://localhost:3000/health"] interval: 30s timeout: 10s retries: 3 start_period: 40s ``` ### 3. Resource Limits ```yaml services: app: deploy: resources: limits: cpus: '0.5' memory: 512M reservations: cpus: '0.25' memory: 256M ``` ### 4. Named Volumes for Persistence ```yaml volumes: postgres-data: driver: local redis-data: driver: local ``` ### 5. Separate Dev/Prod Configs ```bash # Development docker-compose -f docker-compose.yml -f docker-compose.dev.yml up # Production docker-compose -f docker-compose.yml -f docker-compose.prod.yml up ``` ## Troubleshooting ### Port Already in Use ```bash # Find process using port lsof -i :3000 # Change port in docker-compose.yml ports: - "3001:3000" ``` ### Container Won't Start ```bash # Check logs docker-compose logs app # Check service status docker-compose ps # Rebuild without cache docker-compose build --no-cache app ``` ### Database Connection Issues ```bash # Ensure depends_on is set depends_on: - db # Use service name as hostname DATABASE_URL=postgresql://user:pass@db:5432/myapp # Wait for database to be ready (use wait-for-it.sh or healthcheck) ``` ### Volume Permission Issues ```bash # Set user in Dockerfile USER node # Or in docker-compose.yml user: "1000:1000" ``` ## Production Considerations ### 1. Use Specific Image Tags ```yaml # ❌ Don't use latest image: postgres:latest # ✅ Use specific version image: postgres:15.3-alpine ``` ### 2. Secrets Management ```yaml # Use Docker secrets (Swarm mode) secrets: db_password: file: ./secrets/db_password.txt services: db: secrets: - db_password ``` ### 3. Logging ```yaml services: app: logging: driver: "json-file" options: max-size: "10m" max-file: "3" ``` ### 4. Restart Policies ```yaml services: app: restart: unless-stopped ``` ## Integration with CI/CD ```yaml # .github/workflows/test.yml - name: Run tests run: | docker-compose -f docker-compose.test.yml up --abort-on-container-exit docker-compose -f docker-compose.test.yml down -v ``` ## Common Stacks ### MERN Stack ```yaml services: frontend: build: ./frontend ports: - "3000:3000" backend: build: ./backend ports: - "5000:5000" mongo: image: mongo:6 volumes: - mongo-data:/data/db ``` ### Django + PostgreSQL + Redis ```yaml services: web: build: . command: python manage.py runserver 0.0.0.0:8000 ports: - "8000:8000" depends_on: - db - redis db: image: postgres:15 redis: image: redis:7-alpine celery: build: . command: celery -A myapp worker -l info depends_on: - redis ``` ## References - [Docker Compose Documentation](https://docs.docker.com/compose/) - [Compose File Reference](https://docs.docker.com/compose/compose-file/) - [Best Practices](https://docs.docker.com/develop/dev-best-practices/)