Service 概念与实现

apiVersion: v1
kind: Service
metadata:
  name: my-service
  namespace: default
spec:
  # Service 类型
  type: ClusterIP

  # 选择器：匹配 Pod 标签
  selector:
    app: my-app
    version: v1

  # 端口定义
  ports:
    - name: http
      protocol: TCP
      port: 80        # Service 端口
      targetPort: 8080 # Pod 端口

  # 会话亲和性
  sessionAffinity: None
  # sessionAffinityConfig:
  #   clientIP:
  #     timeoutSeconds: 10800

  # ClusterIP（可选，自动分配）
  # clusterIP: 10.96.0.100

  # 内部流量策略
  internalTrafficPolicy: Cluster

apiVersion: v1
kind: Service
metadata:
  name: internal-service
spec:
  type: ClusterIP  # 默认类型
  selector:
    app: backend
  ports:
    - port: 80
      targetPort: 8080

apiVersion: v1
kind: Service
metadata:
  name: nodeport-service
spec:
  type: NodePort
  selector:
    app: web
  ports:
    - port: 80
      targetPort: 8080
      nodePort: 30080  # 范围：30000-32767

apiVersion: v1
kind: Service
metadata:
  name: loadbalancer-service
spec:
  type: LoadBalancer
  selector:
    app: web
  ports:
    - port: 80
      targetPort: 8080
  # 云提供商特定注解
  # annotations:
  #   service.beta.kubernetes.io/aws-load-balancer-type: nlb

apiVersion: v1
kind: Service
metadata:
  name: external-db
spec:
  type: ExternalName
  externalName: db.example.com  # 外部服务 DNS

apiVersion: v1
kind: Service
metadata:
  name: headless-service
spec:
  clusterIP: None  # 关键配置
  selector:
    app: stateful-app
  ports:
    - port: 80
      targetPort: 8080

apiVersion: v1
kind: Endpoints
metadata:
  name: my-service  # 与 Service 同名
  namespace: default
subsets:
  - addresses:
      # Ready Pod 的 IP
      - ip: 10.244.1.2
        nodeName: node1
        targetRef:
          kind: Pod
          name: my-pod-1
          namespace: default
      - ip: 10.244.2.3
        nodeName: node2
        targetRef:
          kind: Pod
          name: my-pod-2
          namespace: default
    # NotReady Pod 的 IP
    notReadyAddresses:
      - ip: 10.244.3.4
        nodeName: node3
        targetRef:
          kind: Pod
          name: my-pod-3
          namespace: default
    ports:
      - name: http
        port: 8080
        protocol: TCP

// pkg/controller/endpoint/endpoints_controller.go

// syncService 同步 Service 的 Endpoints
func (e *Controller) syncService(key string) error {
    namespace, name, err := cache.SplitMetaNamespaceKey(key)
    if err != nil {
        return err
    }

    // 获取 Service
    service, err := e.serviceLister.Services(namespace).Get(name)
    if errors.IsNotFound(err) {
        // Service 不存在，删除对应的 Endpoints
        return e.client.CoreV1().Endpoints(namespace).Delete(
            context.TODO(), name, metav1.DeleteOptions{})
    }
    if err != nil {
        return err
    }

    // 无选择器的 Service 不管理 Endpoints
    if service.Spec.Selector == nil {
        return nil
    }

    // 获取匹配的 Pod
    pods, err := e.podLister.Pods(namespace).List(
        labels.SelectorFromSet(service.Spec.Selector))
    if err != nil {
        return err
    }

    // 构建 Endpoints subsets
    subsets := []v1.EndpointSubset{}
    for _, pod := range pods {
        if !IsPodReady(pod) {
            // NotReady Pod 放入 notReadyAddresses
            continue
        }

        // 获取 Pod IP
        if pod.Status.PodIP == "" {
            continue
        }

        // 构建 EndpointAddress
        epa := v1.EndpointAddress{
            IP:       pod.Status.PodIP,
            NodeName: &pod.Spec.NodeName,
            TargetRef: &v1.ObjectReference{
                Kind:      "Pod",
                Namespace: pod.Namespace,
                Name:      pod.Name,
                UID:       pod.UID,
            },
        }

        // 添加到对应的 subset
        subsets = addToSubsets(subsets, epa, service.Spec.Ports)
    }

    // 创建或更新 Endpoints
    currentEndpoints, err := e.endpointsLister.Endpoints(namespace).Get(name)
    if errors.IsNotFound(err) {
        // 创建新的 Endpoints
        newEndpoints := &v1.Endpoints{
            ObjectMeta: metav1.ObjectMeta{
                Name:      name,
                Namespace: namespace,
                Labels:    service.Labels,
            },
            Subsets: subsets,
        }
        _, err = e.client.CoreV1().Endpoints(namespace).Create(
            context.TODO(), newEndpoints, metav1.CreateOptions{})
        return err
    }

    // 更新现有 Endpoints
    if !endpointsEqual(currentEndpoints.Subsets, subsets) {
        newEndpoints := currentEndpoints.DeepCopy()
        newEndpoints.Subsets = subsets
        _, err = e.client.CoreV1().Endpoints(namespace).Update(
            context.TODO(), newEndpoints, metav1.UpdateOptions{})
        return err
    }

    return nil
}

apiVersion: v1
kind: Service
metadata:
  name: sticky-service
spec:
  selector:
    app: web
  ports:
    - port: 80
      targetPort: 8080
  sessionAffinity: ClientIP
  sessionAffinityConfig:
    clientIP:
      timeoutSeconds: 10800  # 3 小时

// kube-proxy iptables 模式实现会话亲和

// 对于 ClientIP 亲和性，使用 recent 模块
// -A KUBE-SEP-XXX -m recent --name KUBE-SEP-XXX --rcheck --seconds 10800 --reap
//    -j KUBE-MARK-MASQ
// -A KUBE-SEP-XXX -m recent --name KUBE-SEP-XXX --set -j DNAT --to-destination 10.244.1.2:8080

// IPVS 模式使用连接表实现亲和性
// ipvsadm -A -t 10.96.0.100:80 -s rr -p 10800

apiVersion: v1
kind: Service
metadata:
  name: local-traffic-service
spec:
  selector:
    app: web
  ports:
    - port: 80
  # 内部流量策略
  internalTrafficPolicy: Local  # 或 Cluster

apiVersion: v1
kind: Service
metadata:
  name: external-traffic-service
spec:
  type: LoadBalancer
  selector:
    app: web
  ports:
    - port: 80
  # 外部流量策略
  externalTrafficPolicy: Local  # 或 Cluster

apiVersion: v1
kind: Service
metadata:
  name: topology-aware-service
  annotations:
    # 启用拓扑感知提示
    service.kubernetes.io/topology-mode: Auto
spec:
  selector:
    app: web
  ports:
    - port: 80

apiVersion: discovery.k8s.io/v1
kind: EndpointSlice
metadata:
  name: my-service-abc
  labels:
    kubernetes.io/service-name: my-service
addressType: IPv4
endpoints:
  - addresses:
      - "10.244.1.2"
    conditions:
      ready: true
    zone: "us-west-2a"  # 区域信息
    hints:
      forZones:
        - name: "us-west-2a"  # 提示优先使用此端点的区域
  - addresses:
      - "10.244.2.3"
    conditions:
      ready: true
    zone: "us-west-2b"
    hints:
      forZones:
        - name: "us-west-2b"
ports:
  - port: 8080
    protocol: TCP

# Service 无选择器
apiVersion: v1
kind: Service
metadata:
  name: external-database
spec:
  ports:
    - port: 5432
      targetPort: 5432
---
# 手动创建 Endpoints
apiVersion: v1
kind: Endpoints
metadata:
  name: external-database  # 与 Service 同名
subsets:
  - addresses:
      - ip: 192.168.1.100  # 外部数据库 IP
      - ip: 192.168.1.101
    ports:
      - port: 5432