Docker Compose Fundamentals

docker compose version     # Docker Compose version v5.5.1

# compose.yaml -- development only: the credentials below are placeholders, not real secrets
name: orders

services:
  api:
    build: .                                   # or: image: ghcr.io/myorg/orders-service:1.4.0
    ports:
      - "127.0.0.1:8080:8080"
    environment:
      SPRING_DATASOURCE_URL: jdbc:postgresql://db:5432/orders
      SPRING_DATASOURCE_USERNAME: orders
      SPRING_DATASOURCE_PASSWORD: ${DB_PASSWORD:-dev-only-password}
    depends_on:
      db:
        condition: service_healthy
    restart: unless-stopped
    deploy:
      resources:
        limits:
          cpus: "1.5"
          memory: 768M

  db:
    image: postgres:18.1
    environment:
      POSTGRES_DB: orders
      POSTGRES_USER: orders
      POSTGRES_PASSWORD: ${DB_PASSWORD:-dev-only-password}
    volumes:
      - db-data:/var/lib/postgresql
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U orders -d orders"]
      interval: 5s
      timeout: 3s
      retries: 10
      start_period: 10s

  adminer:
    image: adminer:5
    ports:
      - "127.0.0.1:8081:8080"
    profiles: ["tools"]                        # only started with --profile tools

volumes:
  db-data:

docker compose up -d --build        # build api, create network and volume, start db, wait until healthy, start api
docker compose ps
docker compose logs -f api
docker compose exec db psql -U orders -d orders
docker compose --profile tools up -d
docker compose down                 # stop and remove containers and the network; keep the volume
docker compose down -v              # ... and remove the named volumes too

cat > .env <<EOF
DB_PASSWORD=local-placeholder
EOF
docker compose config          # the fully resolved model: interpolated, merged, validated
docker compose config --environment

docker compose up -d --build --wait   # start in the background; --wait blocks until services are healthy
docker compose ps -a
docker compose logs -f --tail 100 api
docker compose exec api sh            # a shell in a running service container
docker compose run --rm api ./mvnw -q test   # a one-off container for the service
docker compose restart api
docker compose pull                   # fetch newer images for image-based services
docker compose watch                  # sync or rebuild on file changes (see Compose in Practice)
docker compose down -v --remove-orphans

# 2015: docker-compose.yml for Compose v1 (file format 1, no services key) -- historical
web:
  build: .
  links:
    - redis
  ports:
    - "5000:5000"
redis:
  image: redis

# compose.yaml, run with: docker compose up -d
services:
  web:
    build: .
    ports:
      - "127.0.0.1:5000:5000"
    depends_on:
      - redis
  redis:
    image: redis:8.2