Docker Compose

Orchestrate multi-container applications with declarative YAML configuration.

When to Use This Skill

Use this skill when:

• Running multi-container applications locally
• Setting up development environments
• Defining service dependencies and networking
• Managing application stacks with multiple services
• Creating reproducible development setups

Execution Scope

Confirm the selected Docker context and project before any operation. Build instructions execute contributed commands; inspect the Dockerfile, build context, scripts and downloaded dependencies first. Image publication, shared-container stops and volume deletion need authorization for the exact target. Do not expose environment values, image history or logs containing credentials. These examples are independent fragments with project-specific assets, not a complete deployment.

Prerequisites

• Docker Engine with Compose plugin (v2)
• Basic Docker knowledge
• YAML syntax understanding

Basic Configuration

Simple Application Stack

# docker-compose.yml

services:
  web:
    build: .
    ports:
      - "127.0.0.1:3000:3000"
    environment:
      - NODE_ENV=development
      - DATABASE_URL=postgres://postgres:${POSTGRES_PASSWORD:?set a local fixture password}@db:5432/myapp
    depends_on:
      - db
      - redis

  db:
    image: postgres:15-alpine
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:?set a local fixture password}
      POSTGRES_DB: myapp
    volumes:
      - postgres-data:/var/lib/postgresql/data
    ports:
      - "127.0.0.1:5432:5432"

  redis:
    image: redis:7-alpine
    ports:
      - "127.0.0.1:6379:6379"

volumes:
  postgres-data:

Service Configuration

Build Options

services:
  app:
    build:
      context: ./app
      dockerfile: Dockerfile.dev
      args:
        NODE_VERSION: "20"
      target: development
      cache_from:
        - myapp:cache
    image: myapp:dev

Environment Variables

services:
  app:
    environment:
      - NODE_ENV=production
      - API_KEY=${API_KEY}  # From shell or .env file
    env_file:
      - .env
      - .env.local

Port Mapping

services:
  web:
    ports:
      - "127.0.0.1:3000:3000"           # HOST:CONTAINER
      - "127.0.0.1:9229:9229" # Bind to localhost only
      - "8080-8090:8080-8090" # Port range
    expose:
      - "3000"                # Internal only (no host binding)

Volume Mounts

services:
  app:
    volumes:
      # Named volume
      - app-data:/app/data
      # Bind mount
      - ./src:/app/src
      # Read-only bind mount
      - ./config:/app/config:ro
      # Anonymous volume (for node_modules)
      - /app/node_modules

volumes:
  app-data:
    driver: local

Dependencies

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

  db:
    image: postgres:15
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 10s
      timeout: 5s
      retries: 5

Networking

Custom Networks

services:
  frontend:
    networks:
      - frontend-net

  backend:
    networks:
      - frontend-net
      - backend-net

  db:
    networks:
      - backend-net

networks:
  frontend-net:
    driver: bridge
  backend-net:
    driver: bridge
    internal: true  # No external access

Network Aliases

services:
  db:
    networks:
      backend:
        aliases:
          - database
          - postgres

networks:
  backend:

Resource Limits

services:
  app:
    deploy:
      resources:
        limits:
          cpus: '2'
          memory: 1G
        reservations:
          cpus: '0.5'
          memory: 256M

Multiple Compose Files

Override Files

# docker-compose.yml (base)
services:
  web:
    image: myapp:latest
    ports:
      - "127.0.0.1:3000:3000"

# docker-compose.override.yml (development - auto-loaded)
services:
  web:
    build: .
    volumes:
      - ./src:/app/src
    environment:
      - DEBUG=true

# docker-compose.prod.yml (production)
services:
  web:
    deploy:
      replicas: 3
    environment:
      - DEBUG=false

Using Multiple Files

# Development (uses override automatically)
docker compose up

# Production
docker compose -f docker-compose.yml -f docker-compose.prod.yml up

# Merge and view final config

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