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

Prerequisites

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

Basic Configuration

Simple Application Stack

# docker-compose.yml
version: '3.8'

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=development
      - DATABASE_URL=postgres://postgres:secret@db:5432/myapp
    depends_on:
      - db
      - redis

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

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