docker-patterns

name	docker-patterns
description	Docker and Docker Compose patterns for local development, container security, networking, volume strategies, and multi-service orchestration.
origin	ECC

Docker Patterns

コンテナ化された開発のための Docker と Docker Compose のベストプラクティスです。

起動条件

• ローカル開発用の Docker Compose のセットアップ
• マルチコンテナアーキテクチャの設計
• コンテナのネットワーキングやボリュームの問題のトラブルシューティング
• Dockerfile のセキュリティとサイズのレビュー
• ローカル開発からコンテナ化ワークフローへの移行

ローカル開発用 Docker Compose

標準的な Web アプリスタック

# docker-compose.yml
services:
  app:
    build:
      context: .
      target: dev                     # Use dev stage of multi-stage Dockerfile
    ports:
      - "3000:3000"
    volumes:
      - .:/app                        # Bind mount for hot reload
      - /app/node_modules             # Anonymous volume -- preserves container deps
    environment:
      - DATABASE_URL=postgres://postgres:postgres@db:5432/app_dev
      - REDIS_URL=redis://redis:6379/0
      - NODE_ENV=development
    depends_on:
      db:
        condition: service_healthy
      redis:
        condition: service_started
    command: npm run dev

  db:
    image: postgres:16-alpine
    ports:
      - "5432:5432"
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: app_dev
    volumes:
      - pgdata:/var/lib/postgresql/data
      - ./scripts/init-db.sql:/docker-entrypoint-initdb.d/init.sql
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 3s
      retries: 5

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    volumes:
      - redisdata:/data

  mailpit:                            # Local email testing
    image: axllent/mailpit
    ports:
      - "8025:8025"                   # Web UI
      - "1025:1025"                   # SMTP

volumes:
  pgdata:
  redisdata:

開発用 vs 本番用 Dockerfile

# Stage: dependencies
FROM node:22-alpine AS deps
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci

# Stage: dev (hot reload, debug tools)
FROM node:22-alpine AS dev
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
EXPOSE 3000
CMD ["npm", "run", "dev"]

# Stage: build
FROM node:22-alpine AS build
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
RUN npm run build && npm prune --production

# Stage: production (minimal image)
FROM node:22-alpine AS production
WORKDIR /app
RUN addgroup -g 1001 -S appgroup && adduser -S appuser -u 1001
USER appuser
COPY --from=build --chown=appuser:appgroup /app/dist ./dist
COPY --from=build --chown=appuser:appgroup /app/node_modules ./node_modules
COPY --from=build --chown=appuser:appgroup /app/package.json ./
ENV NODE_ENV=production
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=3s CMD wget -qO- http://localhost:3000/health || exit 1
CMD ["node", "dist/server.js"]

Override ファイル

# docker-compose.override.yml (auto-loaded, dev-only settings)
services:
  app:
    environment:
      - DEBUG=app:*
      - LOG_LEVEL=debug
    ports:
      - "9229:9229"                   # Node.js debugger

# docker-compose.prod.yml (explicit for production)
services:
  app:
    build:
      target: production
    restart: always
    deploy:
      resources:
        limits:
          cpus: "1.0"
          memory: 512M

# Development (auto-loads override)
docker compose up

# Production
docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d

ネットワーキング

サービスディスカバリー

同じ Compose ネットワーク内のサービスはサービス名で解決されます：

# From "app" container:
postgres://postgres:postgres@db:5432/app_dev    # "db" resolves to the db container
redis://redis:6379/0                             # "redis" resolves to the redis container

カスタムネットワーク

services:
  frontend:
    networks:
      - frontend-net

  api:
    networks:
      - frontend-net
      - backend-net

  db:
    networks:
      - backend-net              # Only reachable from api, not frontend

networks:
  frontend-net:
  backend-net:

必要なものだけを公開

services:
  db:
    ports:
      - "127.0.0.1:5432:5432"   # Only accessible from host, not network
    # Omit ports entirely in production -- accessible only within Docker network

ボリューム戦略

volumes:
  # Named volume: persists across container restarts, managed by Docker
  pgdata:

  # Bind mount: maps host directory into container (for development)
  # - ./src:/app/src

  # Anonymous volume: preserves container-generated content from bind mount override
  # - /app/node_modules

一般的なパターン

services:
  app:
    volumes:
      - .:/app                   # Source code (bind mount for hot reload)
      - /app/node_modules        # Protect container's node_modules from host
      - /app/.next               # Protect build cache

  db:
    volumes:
      - pgdata:/var/lib/postgresql/data          # Persistent data
      - ./scripts/init.sql:/docker-entrypoint-initdb.d/init.sql  # Init scripts

コンテナセキュリティ

Dockerfile のハードニング

# 1. Use specific tags (never :latest)
FROM node:22.12-alpine3.20

# 2. Run as non-root
RUN addgroup -g 1001 -S app && adduser -S app -u 1001
USER app

# 3. Drop capabilities (in compose)
# 4. Read-only root filesystem where possible
# 5. No secrets in image layers

Compose のセキュリティ

services:
  app:
    security_opt:
      - no-new-privileges:true
    read_only: true
    tmpfs:
      - /tmp
      - /app/.cache
    cap_drop:
      - ALL
    cap_add:
      - NET_BIND_SERVICE          # Only if binding to ports < 1024

シークレット管理

# GOOD: Use environment variables (injected at runtime)
services:
  app:
    env_file:
      - .env                     # Never commit .env to git
    environment:
      - API_KEY                  # Inherits from host environment

# GOOD: Docker secrets (Swarm mode)
secrets:
  db_password:
    file: ./secrets/db_password.txt

services:
  db:
    secrets:
      - db_password

# BAD: Hardcoded in image
# ENV API_KEY=sk-proj-xxxxx      # NEVER DO THIS

.dockerignore

node_modules
.git
.env
.env.*
dist
coverage
*.log
.next
.cache
docker-compose*.yml
Dockerfile*
README.md
tests/

デバッグ

よく使うコマンド

# View logs
docker compose logs -f app           # Follow app logs
docker compose logs --tail=50 db     # Last 50 lines from db

# Execute commands in running container
docker compose exec app sh           # Shell into app
docker compose exec db psql -U postgres  # Connect to postgres

# Inspect
docker compose ps                     # Running services
docker compose top                    # Processes in each container
docker stats                          # Resource usage

# Rebuild
docker compose up --build             # Rebuild images
docker compose build --no-cache app   # Force full rebuild

# Clean up
docker compose down                   # Stop and remove containers
docker compose down -v                # Also remove volumes (DESTRUCTIVE)
docker system prune                   # Remove unused images/containers

ネットワーク問題のデバッグ

# Check DNS resolution inside container
docker compose exec app nslookup db

# Check connectivity
docker compose exec app wget -qO- http://api:3000/health

# Inspect network
docker network ls
docker network inspect <project>_default

アンチパターン

# BAD: オーケストレーションなしで本番環境に docker compose を使用
# 本番のマルチコンテナワークロードには Kubernetes、ECS、Docker Swarm を使用

# BAD: ボリュームなしでコンテナにデータを保存
# コンテナはエフェメラル — ボリュームなしでは再起動時にすべてのデータが失われる

# BAD: root として実行
# 常に非 root ユーザーを作成して使用

# BAD: :latest タグの使用
# 再現可能なビルドのために特定のバージョンに固定

# BAD: すべてのサービスを1つの巨大なコンテナに
# 関心事を分離：1コンテナにつき1プロセス

# BAD: docker-compose.yml にシークレットを記述
# .env ファイル（gitignore 済み）または Docker secrets を使用