Docker Compose 2026: マルチコンテナアプリケーション、ネットワーキング、DevOps面接質問集

# compose.yaml
services:
  api:
    build: ./api
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgres://db:5432/app
    depends_on:
      db:
        condition: service_healthy
    networks:
      - backend

  db:
    image: postgres:16
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      - POSTGRES_DB=app
      - POSTGRES_PASSWORD_FILE=/run/secrets/db_password
    secrets:
      - db_password
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 5s
      retries: 5
    networks:
      - backend

networks:
  backend:
    driver: bridge

volumes:
  postgres_data:

secrets:
  db_password:
    file: ./secrets/db_password.txt

# compose.yaml
services:
  frontend:
    build: ./frontend
    ports:
      - "80:80"
    networks:
      - frontend-net
      - backend-net

  api:
    build: ./api
    networks:
      - backend-net

  cache:
    image: redis:7-alpine
    networks:
      - backend-net

  db:
    image: postgres:16
    networks:
      - backend-net

networks:
  frontend-net:
    driver: bridge
  backend-net:
    driver: bridge
    internal: true

# api/Dockerfile
# Stage 1: Build
FROM node:22-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Stage 2: Production
FROM node:22-alpine AS production
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY package*.json ./
USER node
EXPOSE 3000
CMD ["node", "dist/index.js"]

# Stage 3: Development
FROM node:22-alpine AS development
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
USER node
CMD ["npm", "run", "dev"]

# compose.yaml
services:
  api:
    build:
      context: ./api
      target: ${BUILD_TARGET:-production}
    volumes:
      - ${API_VOLUMES:-./api/dist:/app/dist:ro}
    profiles:
      - ${COMPOSE_PROFILES:-prod}

# compose.yaml
services:
  api:
    build: ./api
    depends_on:
      db:
        condition: service_healthy
      cache:
        condition: service_started
      migrations:
        condition: service_completed_successfully

  migrations:
    build: ./api
    command: npm run migrate
    depends_on:
      db:
        condition: service_healthy

  db:
    image: postgres:16
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 3s
      retries: 5
      start_period: 10s

  cache:
    image: redis:7-alpine
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 5s
      timeout: 3s
      retries: 3

# compose.yaml (基本設定)
services:
  api:
    build: ./api
    environment:
      - NODE_ENV=production

  db:
    image: postgres:16

# compose.override.yaml (開発用オーバーライド)
services:
  api:
    build:
      target: development
    volumes:
      - ./api:/app
      - /app/node_modules
    environment:
      - NODE_ENV=development
      - DEBUG=app:*
    ports:
      - "9229:9229"

  db:
    ports:
      - "5432:5432"

# compose.prod.yaml
services:
  api:
    image: registry.example.com/api:${VERSION:-latest}
    deploy:
      replicas: 3
      resources:
        limits:
          cpus: "0.5"
          memory: 512M
        reservations:
          cpus: "0.25"
          memory: 256M
      restart_policy:
        condition: on-failure
        delay: 5s
        max_attempts: 3
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"

  nginx:
    image: nginx:alpine
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
      - ./certs:/etc/nginx/certs:ro
    depends_on:
      - api

# .env
POSTGRES_PASSWORD=dev_password_only
API_SECRET_KEY=local_dev_key

# compose.yaml
services:
  api:
    environment:
      - API_SECRET_KEY  # シェルまたは.envから継承
      - DATABASE_URL=postgres://user:${POSTGRES_PASSWORD}@db:5432/app
    env_file:
      - ./config/api.env

# compose.prod.yaml
services:
  api:
    secrets:
      - api_key
      - db_password
    environment:
      - API_KEY_FILE=/run/secrets/api_key

secrets:
  api_key:
    external: true
  db_password:
    file: ./secrets/db_password.txt

services:
  migrate:
    image: api:latest
    command: npm run migrate
    depends_on:
      db:
        condition: service_healthy

  api:
    depends_on:
      migrate:
        condition: service_completed_successfully

# すべてのサービスのログを表示
docker compose logs -f

# タイムスタンプ付きで特定のサービスのログを表示
docker compose logs -f --timestamps api

# 実行中のコンテナでコマンドを実行
docker compose exec api sh

# 単発のコマンドを実行（新しいコンテナを起動）
docker compose run --rm api npm test

# リソース使用状況を表示
docker compose top
docker stats

# ネットワーク設定を調査
docker network inspect project_backend

# composeファイルを検証
docker compose config