K8s新手系列之Endponit

概述

官方文档：https://kubernetes.io/zh-cn/docs/reference/kubernetes-api/service-resources/endpoints-v1/

Endpoint简称ep

Endpoint是kubernetes中的一个资源对象，存储在etcd中，用来记录一个service对应的所有pod的访问地址，它是根据service配置文件中selector描述产生的。

一个Service由一组Pod组成，这些Pod通过Endpoints暴露出来，Endpoints是实现实际服务的端点集合。换句话说，service和pod之间的联系是通过endpoints实现的。

负载分发策略

对Service的访问被分发到了后端的Pod上去，目前kubernetes提供了两种负载分发策略：

• 如果不定义，默认使用kube-proxy的策略，比如随机、轮询
• 基于客户端地址的会话保持模式，即来自同一个客户端发起的所有请求都会转发到固定的一个Pod上，此模式可以使在spec中添加sessionAffinity:ClientIP选项

验证Endpoint

创建service和deploy

[root@master01 ~/ingress]# cat nginx-deploy.yaml # service apiVersion: v1 kind: Service metadata:   namespace: default   name: nginx-svc-clusterip spec:   type: ClusterIP   selector:     app: nginx   ports:   - name: clusterip-nginx     port: 80     targetPort: 80     protocol: TCP  --- # deploy apiVersion: apps/v1 kind: Deployment metadata:   name: deployment-nginx   namespace: default spec:   replicas: 3   selector:     matchLabels:       app: nginx   template:     metadata:       name: pod-nginx       labels:         app: nginx     spec:       containers:       - name: container-nginx         image: nginx:1.14.1       restartPolicy: Always 

查看创建成功对应的资源

# 查看pod [root@master01 ~/ingress]# kubectl get po -o wide NAME                                READY   STATUS             RESTARTS         AGE    IP                NODE     NOMINATED NODE   READINESS GATES deployment-nginx-6d84458cd8-g8lkv   1/1     Running            0                35m    100.117.144.139   node01   <none>           <none> deployment-nginx-6d84458cd8-j8m6c   1/1     Running            0                35m    100.95.185.234    node02   <none>           <none> deployment-nginx-6d84458cd8-znr7t   1/1     Running            0                35m    100.117.144.140   node01   <none>           <none>  # 查看svc详情，注意Endpoints列表是和pod的IP保持一致的 [root@master01 ~/ingress]# kubectl describe svc nginx-svc-clusterip Name:              nginx-svc-clusterip Namespace:         default Labels:            <none> Annotations:       <none> Selector:          app=nginx Type:              ClusterIP IP Family Policy:  SingleStack IP Families:       IPv4 IP:                10.96.1.52 IPs:               10.96.1.52 Port:              clusterip-nginx  80/TCP TargetPort:        80/TCP Endpoints:         100.117.144.139:80,100.117.144.140:80,100.95.185.234:80 Session Affinity:  None Events:            <none>  # 查看endpoints资源 [root@master01 ~/ingress]# kubectl get endpoints NAME                  ENDPOINTS                                                 AGE nginx-svc-clusterip   100.117.144.139:80,100.117.144.140:80,100.95.185.234:80   36m 

当我们重启Pod之后看看Endpoints列表会发生什么

重启Pod

[root@master01 ~/ingress]# kubectl delete po deployment-nginx-6d84458cd8-g8lkv deployment-nginx-6d84458cd8-j8m6c deployment-nginx-6d84458cd8-znr7t pod "deployment-nginx-6d84458cd8-g8lkv" deleted pod "deployment-nginx-6d84458cd8-j8m6c" deleted pod "deployment-nginx-6d84458cd8-znr7t" deleted 

查看资源，发现对应的IP是会进行变化的

# 查看Pod [root@master01 ~/ingress]# kubectl get po -o wide NAME                                READY   STATUS             RESTARTS         AGE    IP                NODE     NOMINATED NODE   READINESS GATES deployment-nginx-6d84458cd8-4z4cb   1/1     Running            0                7s     100.95.185.236    node02   <none>           <none> deployment-nginx-6d84458cd8-ht2z9   1/1     Running            0                7s     100.117.144.141   node01   <none>           <none> deployment-nginx-6d84458cd8-ns47j   1/1     Running            0                7s     100.95.185.238    node02   <none>           <none> # 查看service [root@master01 ~/ingress]# kubectl describe svc nginx-svc-clusterip Name:              nginx-svc-clusterip Namespace:         default Labels:            <none> Annotations:       <none> Selector:          app=nginx Type:              ClusterIP IP Family Policy:  SingleStack IP Families:       IPv4 IP:                10.96.1.52 IPs:               10.96.1.52 Port:              clusterip-nginx  80/TCP TargetPort:        80/TCP Endpoints:         100.117.144.141:80,100.95.185.236:80,100.95.185.238:80 Session Affinity:  None Events:            <none> #查看endpoints [root@master01 ~/ingress]# kubectl get endpoints NAME                  ENDPOINTS                                                AGE kubernetes            10.0.0.30:6443                                           78m nginx-svc-clusterip   100.117.144.141:80,100.95.185.236:80,100.95.185.238:80   39m  

编写一个属于自己Endpoints

Endpoints资源是通过name和namespace两个字段与Service进行关联的，所以Endpoints的名称和Service的名称相同.

示例：

[root@master01 ~]# cat ep.yaml # Endpoints资源 apiVersion: v1 kind: Endpoints metadata:     name: harbor-huangxin subsets:     - addresses:       - ip: 10.0.0.250       ports:       - port: 80         protocol: TCP --- # Service资源 apiVersion: v1 kind: Service metadata:     name: harbor-huangxin spec:     type: ClusterIP     ports:         - port: 80           targetPort: 80 

查看一下资源

# 查看service [root@master01 ~]# kubectl describe svc endpoint-huangsir Name:              endpoint-huangsir Namespace:         default Labels:            <none> Annotations:       <none> Selector:          <none> Type:              ClusterIP IP Family Policy:  SingleStack IP Families:       IPv4 IP:                10.96.1.127 IPs:               10.96.1.127 Port:              <unset>  80/TCP TargetPort:        80/TCP Endpoints:         10.0.0.250:80 Session Affinity:  None Events:            <none> # 查看endpoint [root@master01 ~]# kubectl get ep endpoint-huangsir NAME              ENDPOINTS       AGE endpoint-huangsir   10.0.0.250:80   51s