Docker Compose Basics

Docker Compose for defining and running multi-container applications.

Basic Structure

version: '3.8'

services: web: image: nginx:latest ports: - "80:80" volumes: - ./html:/usr/share/nginx/html environment: - NGINX_HOST=localhost depends_on: - api

api: build: ./api ports: - "3000:3000" environment: DATABASE_URL: postgres://db:5432/myapp depends_on: - db

db: image: postgres:15 volumes: - pgdata:/var/lib/postgresql/data environment: POSTGRES_PASSWORD: secret POSTGRES_DB: myapp

volumes: pgdata:

Common Commands

Start services

docker compose up

Start in background

docker compose up -d

Stop services

docker compose down

View logs

docker compose logs -f

Rebuild

docker compose build

Execute command

docker compose exec web sh

Scale service

docker compose up -d --scale api=3

Best Practices

Environment Variables

services: api: environment: - NODE_ENV=${NODE_ENV:-development} - API_KEY=${API_KEY}

Health Checks

services: web: healthcheck: test: ["CMD", "curl", "-f", "http://localhost"] interval: 30s timeout: 10s retries: 3

Resource Limits

services: api: deploy: resources: limits: cpus: '0.5' memory: 512M