Cloud Native

# Cloud Native 애플리케이션 Dockerfile
# 멀티스테이지 빌드로 이미지 크기 최소화
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production

FROM node:20-alpine AS runner
WORKDIR /app

# 비root 사용자로 실행 (보안)
RUN addgroup -g 1001 -S nodejs
RUN adduser -S nextjs -u 1001

# 빌드 결과물만 복사 (최소 이미지)
COPY --from=builder /app/node_modules ./node_modules
COPY --chown=nextjs:nodejs . .

USER nextjs

# Health Check 엔드포인트
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD wget --no-verbose --tries=1 --spider http://localhost:3000/health || exit 1

# 환경변수로 설정 주입 (12 Factor)
ENV NODE_ENV=production
ENV PORT=3000

EXPOSE 3000

# Graceful Shutdown 지원
CMD ["node", "server.js"]

# Cloud Native 애플리케이션 Kubernetes 매니페스트
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-service
  labels:
    app: my-service
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
      maxSurge: 1
  selector:
    matchLabels:
      app: my-service
  template:
    metadata:
      labels:
        app: my-service
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "3000"
    spec:
      containers:
      - name: my-service
        image: myregistry/my-service:v1.2.3
        ports:
        - containerPort: 3000

        # 환경변수로 설정 (ConfigMap, Secret)
        envFrom:
        - configMapRef:
            name: my-service-config
        - secretRef:
            name: my-service-secrets

        # 리소스 제한 (필수)
        resources:
          requests:
            cpu: "100m"
            memory: "128Mi"
          limits:
            cpu: "500m"
            memory: "512Mi"

        # 헬스체크 (자가 치유)
        livenessProbe:
          httpGet:
            path: /health/live
            port: 3000
          initialDelaySeconds: 10
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /health/ready
            port: 3000
          initialDelaySeconds: 5
          periodSeconds: 5

        # Graceful Shutdown
        lifecycle:
          preStop:
            exec:
              command: ["/bin/sh", "-c", "sleep 10"]

      terminationGracePeriodSeconds: 30
---
# HPA - 자동 스케일링
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-service-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-service
  minReplicas: 3
  maxReplicas: 20
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70

// 12 Factor App 원칙을 따르는 Node.js 애플리케이션
const express = require('express');
const app = express();

// Factor 3: 환경변수로 설정 (Config)
const config = {
  port: process.env.PORT || 3000,
  databaseUrl: process.env.DATABASE_URL,
  redisUrl: process.env.REDIS_URL,
  logLevel: process.env.LOG_LEVEL || 'info',
};

// Factor 11: 로그를 stdout으로 (Logs)
const logger = {
  info: (msg) => console.log(JSON.stringify({ level: 'info', msg, ts: new Date().toISOString() })),
  error: (msg) => console.error(JSON.stringify({ level: 'error', msg, ts: new Date().toISOString() })),
};

// Factor 6: 상태 비저장 프로세스 (Stateless)
// 세션은 Redis 같은 외부 저장소 사용
const session = require('express-session');
const RedisStore = require('connect-redis').default;

app.use(session({
  store: new RedisStore({ url: config.redisUrl }),
  secret: process.env.SESSION_SECRET,
  resave: false,
  saveUninitialized: false,
}));

// Health Check 엔드포인트
app.get('/health/live', (req, res) => res.json({ status: 'alive' }));
app.get('/health/ready', async (req, res) => {
  // DB 연결 확인
  try {
    await db.query('SELECT 1');
    res.json({ status: 'ready' });
  } catch (err) {
    res.status(503).json({ status: 'not ready' });
  }
});

// Factor 9: 빠른 시작과 정상 종료 (Disposability)
const server = app.listen(config.port, () => {
  logger.info(`Server started on port ${config.port}`);
});

// Graceful Shutdown
process.on('SIGTERM', () => {
  logger.info('SIGTERM received, shutting down gracefully');
  server.close(() => {
    logger.info('HTTP server closed');
    // DB 연결 종료
    db.end(() => {
      logger.info('Database connection closed');
      process.exit(0);
    });
  });
  // 10초 후 강제 종료
  setTimeout(() => process.exit(1), 10000);
});