项目实战：微服务与 Ingress

浏览器 http://app.example.com
          │
          ▼
       Ingress (按路径分流)
        ├─ /        → frontend Service
        └─ /api     → backend Service
          │
          ▼
   frontend Deployment      backend Deployment
   (3 副本)                 (3 副本, 读 ConfigMap)

# 后端配置（用 ConfigMap 注入，便于改环境不重打包）
apiVersion: v1
kind: ConfigMap
metadata:
  name: backend-config
data:
  APP_ENV: production
  LOG_LEVEL: info
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: backend
spec:
  replicas: 3
  selector: { matchLabels: { app: backend } }
  template:
    metadata:
      labels: { app: backend }
    spec:
      containers:
        - name: backend
          image: myrepo/backend:1.0
          ports: [{ containerPort: 8080 }]
          envFrom:
            - configMapRef: { name: backend-config }
          resources:
            requests: { cpu: "100m", memory: "128Mi" }
            limits:   { cpu: "500m", memory: "256Mi" }
          readinessProbe:
            httpGet: { path: /health, port: 8080 }
            initialDelaySeconds: 5
            periodSeconds: 5
---
apiVersion: v1
kind: Service
metadata:
  name: backend
spec:
  selector: { app: backend }
  ports: [{ port: 8080, targetPort: 8080 }]
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: frontend
spec:
  replicas: 3
  selector: { matchLabels: { app: frontend } }
  template:
    metadata:
      labels: { app: frontend }
    spec:
      containers:
        - name: frontend
          image: myrepo/frontend:1.0
          ports: [{ containerPort: 80 }]
          resources:
            requests: { cpu: "50m", memory: "64Mi" }
            limits:   { cpu: "200m", memory: "128Mi" }
---
apiVersion: v1
kind: Service
metadata:
  name: frontend
spec:
  selector: { app: frontend }
  ports: [{ port: 80, targetPort: 80 }]
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: app-ingress
spec:
  rules:
    - host: app.example.com
      http:
        paths:
          - path: /api
            pathType: Prefix
            backend:
              service: { name: backend, port: { number: 8080 } }
          - path: /
            pathType: Prefix
            backend:
              service: { name: frontend, port: { number: 80 } }

kubectl apply -f microservices.yaml
 
# 确认所有资源就绪
kubectl get pods
kubectl get ingress app-ingress

# 根路径走前端
curl http://app.example.com/
 
# /api 走后端
curl http://app.example.com/api/users

# 给后端加自动扩缩容（需 requests 已设）
kubectl autoscale deployment backend --cpu-percent=50 --min=3 --max=10
 
# 发布新版本并保留回滚能力
kubectl set image deployment/backend backend=myrepo/backend:2.0
kubectl rollout undo deployment/backend   # 出问题一键回退