Docker Compose

Docker Compose

Define and run multi-container applications with Docker Compose.

What is Docker Compose?

Docker Compose lets you define multi-container applications in a single docker-compose.yml file, then start everything with one command.

Why Compose?

  • Replaces multiple docker run commands with declarative YAML
  • Services automatically get a shared network
  • Dependency management with depends_on
  • Easy environment variable management

Key Commands

bash
docker compose up        # start all services
docker compose up -d     # start in background
docker compose down      # stop and remove containers
docker compose ps        # list running services
docker compose logs -f   # follow logs
docker compose exec service bash  # shell into service

Example

yaml
# docker-compose.yml
version: '3.9'

services:
  # Web application
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=development
      - DATABASE_URL=postgresql://postgres:secret@db:5432/myapp
      - REDIS_URL=redis://cache:6379
    volumes:
      - .:/app           # bind mount for hot reload
      - /app/node_modules # keep container node_modules
    depends_on:
      db:
        condition: service_healthy
      cache:
        condition: service_started
    restart: unless-stopped

  # PostgreSQL database
  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: myapp
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: secret
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 10s
      timeout: 5s
      retries: 5

  # Redis cache
  cache:
    image: redis:7-alpine
    volumes:
      - redis_data:/data

  # Nginx reverse proxy
  nginx:
    image: nginx:alpine
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
      - ./certs:/etc/nginx/certs
    depends_on:
      - app

volumes:
  postgres_data:
  redis_data:
Try it yourself — YAML