Docker Compose Networking, Volumes, and Runtime Controls

services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"

# Maps host port 8080 to container port 80.

services:
  db:
    image: postgres:16
    ports:
      - "127.0.0.1:5432:5432"

# Publishes the service only to the local machine.

services:
  web:
    image: nginx:alpine
    networks: ["frontend"]
  api:
    image: myapi:latest
    networks: ["frontend", "backend"]

networks:
  frontend: {}
  backend: {}

# Defines multiple named networks for segmentation.

services:
  api:
    image: myapi:latest
    networks:
      backend:
        aliases:
          - internal-api

networks:
  backend: {}

# Adds alternate DNS names for a service on a network.

docker compose port web 80

# Shows the host binding for a service port.

services:
  db:
    image: postgres:16
    volumes:
      - pgdata:/var/lib/postgresql/data

volumes:
  pgdata: {}

# Stores database data in a managed named volume.

services:
  app:
    image: node:20
    working_dir: /app
    volumes:
      - ./:/app

# Mounts the current directory into the container.

services:
  nginx:
    image: nginx:alpine
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro

# Mounts a host file as read-only in the container.

services:
  app:
    image: myapp:latest
    tmpfs:
      - /tmp

# Creates an in-memory temporary filesystem for the service.

docker compose down -v

# Tears down the project and deletes named volumes created for it.

services:
  api:
    image: myapi:latest
    secrets:
      - app_key

secrets:
  app_key:
    file: ./secrets/app_key.txt

# Mounts a file-backed secret into the container.

services:
  nginx:
    image: nginx:alpine
    configs:
      - source: nginx_conf
        target: /etc/nginx/conf.d/default.conf

configs:
  nginx_conf:
    file: ./nginx/default.conf

# Provides a structured way to mount a config artifact.

services:
  api:
    image: myapi:latest
    restart: unless-stopped

# Restarts the service unless it is explicitly stopped.

services:
  app:
    image: myapp:latest
    ulimits:
      nofile:
        soft: 65535
        hard: 65535

# Sets per-container ulimits for file handles and similar resources.

services:
  app:
    image: myapp:latest
    extra_hosts:
      - "host.docker.internal:host-gateway"

# Adds static host entries inside the container.