Kubernetes与Java应用编排

Kubernetes（K8s）是容器编排的事实标准，掌握其核心资源对象是Java微服务云原生部署的关键。

核心资源对象

# Deployment：无状态应用部署
apiVersion: apps/v1
kind: Deployment
metadata:
  name: order-service
  labels:
    app: order-service
spec:
  replicas: 3
  selector:
    matchLabels:
      app: order-service
  template:
    metadata:
      labels:
        app: order-service
    spec:
      containers:
        - name: order-service
          image: registry.example.com/order-service:1.0.0
          ports:
            - containerPort: 8080
          env:
            - name: SPRING_PROFILES_ACTIVE
              value: "prod"
            - name: JAVA_OPTS
              value: "-XX:+UseContainerSupport -XX:MaxRAMPercentage=75.0"
          resources:
            requests:
              memory: "512Mi"
              cpu: "500m"
            limits:
              memory: "1Gi"
              cpu: "1000m"
          livenessProbe:
            httpGet:
              path: /actuator/health/liveness
              port: 8080
            initialDelaySeconds: 60
            periodSeconds: 10
          readinessProbe:
            httpGet:
              path: /actuator/health/readiness
              port: 8080
            initialDelaySeconds: 30
            periodSeconds: 5

Service服务发现

apiVersion: v1
kind: Service
metadata:
  name: order-service
spec:
  selector:
    app: order-service
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
  type: ClusterIP

HPA自动扩缩容

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: order-service-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: order-service
  minReplicas: 2
  maxReplicas: 10
  metrics:
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: 70
    - type: Resource
      resource:
        name: memory
        target:
          type: Utilization
          averageUtilization: 80

ConfigMap与Secret

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  application.yml: |
    spring:
      datasource:
        url: jdbc:mysql://mysql:3306/mydb
---
apiVersion: v1
kind: Secret
metadata:
  name: app-secret
type: Opaque
data:
  db-password: cGFzc3dvcmQxMjM=

Ingress配置

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: api-gateway
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
    - host: api.example.com
      http:
        paths:
          - path: /order
            pathType: Prefix
            backend:
              service:
                name: order-service
                port:
                  number: 80

Java健康检查端点

@Component
@RequiredArgsConstructor
public class KubernetesHealthIndicator implements HealthIndicator {
    private final DataSource dataSource;

    @Override
    public Health health() {
        try (Connection conn = dataSource.getConnection()) {
            return Health.up().build();
        } catch (Exception e) {
            return Health.down(e).build();
        }
    }
}

小结

K8s为Java应用提供自动扩缩容、服务发现、健康检查等能力，是云原生微服务的基础平台。