Java 部署滚动更新的方法(K8s RollingUpdate 策略)

strategy:
  type: RollingUpdate
  rollingUpdate:
    maxUnavailable: 25%
    maxSurge: 25%

// src/main/java/com/example/rollingupdate/DemoApplication.java
package com.example.rollingupdate;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

// src/main/java/com/example/rollingupdate/HelloController.java
package com.example.rollingupdate;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
    @GetMapping("/hello")
    public String hello() {
        return "Hello from Java App v1! 🌟";
    }
    // 模拟版本信息，便于观察更新效果
    @GetMapping("/version")
    public String version() {
        return "v1.0.0";
    }
}

# src/main/resources/application.yml
management:
  endpoints:
    web:
      exposure:
        include: health,info
  endpoint:
    health:
      show-details: always

# Dockerfile
FROM eclipse-temurin:17-jre-alpine
WORKDIR /app
COPY target/*.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

./mvnw clean package -DskipTests
docker build -t yourname/java-rolling-demo:v1 .
docker push yourname/java-rolling-demo:v1

apiVersion: apps/v1
kind: Deployment
metadata:
  name: java-rolling-demo
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
      maxSurge: 1
  selector:
    matchLabels:
      app: java-rolling-demo
  template:
    metadata:
      labels:
        app: java-rolling-demo
    spec:
      containers:
      - name: app
        image: yourname/java-rolling-demo:v1
        ports:
        - containerPort: 8080
        livenessProbe:
          httpGet:
            path: /actuator/health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /actuator/health
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5
        resources:
          requests:
            memory: "256Mi"
            cpu: "100m"
          limits:
            memory: "512Mi"
            cpu: "200m"
---
apiVersion: v1
kind: Service
metadata:
  name: java-rolling-demo-svc
spec:
  selector:
    app: java-rolling-demo
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
  type: ClusterIP

kubectl apply -f deployment.yaml

kubectl get pods -l app=java-rolling-demo

NAME                                 READY   STATUS    RESTARTS   AGE
java-rolling-demo-7d5b8c9f45-abc12   1/1     Running   0          2m
java-rolling-demo-7d5b8c9f45-def34   1/1     Running   0          2m
java-rolling-demo-7d5b8c9f45-ghi56   1/1     Running   0          2m

# 获取 Service IP（或使用 NodePort/Ingress）
kubectl get svc java-rolling-demo-svc
# 使用 curl 测试（假设已暴露到外部）
curl http://<SERVICE-IP>/version
# 返回: v1.0.0

@GetMapping("/version")
public String version() {
    return "v2.0.0"; // 改为 v2
}

@GetMapping("/hello")
public String hello() {
    return "Hello from Java App v2! 🚀";
}

./mvnw clean package -DskipTests
docker build -t yourname/java-rolling-demo:v2 .
docker push yourname/java-rolling-demo:v2

kubectl apply -f deployment.yaml

kubectl set image deployment/java-rolling-demo app=yourname/java-rolling-demo:v2

kubectl rollout status deployment/java-rolling-demo

Waiting for deployment "java-rolling-demo" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "java-rolling-demo" rollout to finish: 2 out of 3 new replicas have been updated...
deployment "java-rolling-demo" successfully rolled out

kubectl get pods -w -l app=java-rolling-demo

NAME                                 READY   STATUS              RESTARTS   AGE
java-rolling-demo-7d5b8c9f45-abc12   1/1     Running             0          5m
java-rolling-demo-7d5b8c9f45-def34   1/1     Running             0          5m
java-rolling-demo-7d5b8c9f45-ghi56   1/1     Running             0          5m
java-rolling-demo-6b8d9f7c54-jkl78   0/1     ContainerCreating   0          1s
java-rolling-demo-6b8d9f7c54-jkl78   1/1     Running             0          10s
java-rolling-demo-7d5b8c9f45-abc12   1/1     Terminating         0          5m30s
...

for i in {1..10}; do curl -s http://<SERVICE-IP>/version; echo; done

@Component
public class DatabaseHealthIndicator implements HealthIndicator {
    @Override
    public Health health() {
        // 检查数据库连接
        if (isDatabaseConnected()) {
            return Health.up().withDetail("database", "available").build();
        }
        return Health.down().withDetail("database", "unavailable").build();
    }
}

kubectl rollout history deployment/java-rolling-demo

REVISION  CHANGE-CAUSE
1         <none>
2         kubectl set image deployment/java-rolling-demo app=yourname/java-rolling-demo:v2

kubectl rollout undo deployment/java-rolling-demo

kubectl rollout undo deployment/java-rolling-demo --to-revision=1

readinessProbe:
  httpGet:
    path: /actuator/health
    port: 8080
  initialDelaySeconds: 20   # 根据应用启动时间调整
  periodSeconds: 5
  timeoutSeconds: 3
  successThreshold: 1
  failureThreshold: 3

containers:
- name: app
  image: yourname/java-rolling-demo:v2
  lifecycle:
    preStop:
      exec:
        command: ["/bin/sh", "-c", "sleep 15"]

# application.yml
server:
  shutdown: graceful
spring:
  lifecycle:
    timeout-per-shutdown-phase: 30s

# 暂停
kubectl rollout pause deployment/java-rolling-demo
# 恢复
kubectl rollout resume deployment/java-rolling-demo