services之Endpoints
Services: 将运行在一组pods上的应用程序公开为网络服务的抽象方法。
1. 为什么需要Services
若我们使用 Deployment 来管理 Pod ， 那么该Deployment可以动态的 创建 和 销毁Pod , 而每个Pod都有自己的IP地址 ， 此时就需要一种服务， 能够帮助我们找到集群对应的 Pod 机器的IP地址,这就需要services。
2. 什么是endpoints
endpoints 资源就是暴露一个服务的IP地址和端口的列表, 只要服务中的 Pod 集合发生改变，endpoints 就会被更新。
默认在创建Servers 时，若编写了标签选择器selector，则会自动创建 endpoints ,否则不会创建。
3. 案例
3.1 创建 deployment
若有deployment资源(该镜像是简单的dns服务器)，定义为如下
apiVersion: apps/v1 kind: Deployment metadata: name: sampledns namespace: default spec: replicas: 3 selector: matchLabels: app: dns template: metadata: labels: app: dns spec: containers: - name: sampledns2 image: docker.io/xxxxxxxx/sample-dns env: - name: redisHost value: '192.168.1.5:6379' - name: proxyDNSHost value: '8.8.8.8' - name: dnsOnlineStatus value: 'false' ports: - name: tcpdns containerPort: 53 protocol: TCP - name: udpdns containerPort: 53 protocol: UDP - name: web containerPort: 5001 protocol: TCP
我们查看pod的状态信息
# kubectl get pods -o wide -l app=dns NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES sampledns-77c56c9fb9-6twzl 1/1 Running 0 2m22s 10.244.2.205 node2 <none> <none> sampledns-77c56c9fb9-g97jw 1/1 Running 0 106s 10.244.1.195 node1 <none> <none> sampledns-77c56c9fb9-l7j5x 1/1 Running 0 2m5s 10.244.1.194 node1 <none> <none> #
3.2 创建 services
创建带 endpoints 的 services
apiVersion: v1 kind: Service metadata: name: dnsservices namespace: default spec: selector: app: dns type: NodePort ports: - name: tcpdns port: 53 targetPort: 53 protocol: TCP - name: udpdns port: 53 targetPort: 53 nodePort: 53 protocol: UDP - name: web port: 5001 targetPort: 5001 nodePort: 5001 protocol: TCP
创建好后，查看 services
# kubectl get services dnsservices -o wide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR dnsservices NodePort 10.1.146.200 <none> 53:53/TCP,53:53/UDP,5001:5001/TCP 8s app=dns #
3.3 观察endpoints
再次查看 endpoints
# kubectl describe endpoints dnsservices Name: dnsservices Namespace: default Labels: <none> Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2022-01-28T10:20:13Z Subsets: Addresses: 10.244.1.194,10.244.1.195,10.244.2.205 NotReadyAddresses: <none> Ports: Name Port Protocol ---- ---- -------- tcpdns 53 TCP udpdns 53 UDP web 5001 TCP Events: <none> #
3.4 重建pods并且查看endpoints
# kubectl delete pod sampledns-77c56c9fb9-6twzl pod "sampledns-77c56c9fb9-6twzl" deleted #
由于使用的 deployment 来定义的 Pod ， 所以，该 Pod 会被重建，如下
# kubectl get pods -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES sampledns-77c56c9fb9-g97jw 1/1 Running 0 8m39s 10.244.1.195 node1 <none> <none> sampledns-77c56c9fb9-gcqcd 1/1 Running 0 28s 10.244.2.206 node2 <none> <none> sampledns-77c56c9fb9-l7j5x 1/1 Running 0 8m58s 10.244.1.194 node1 <none> <none> #
再次查看 endpoints
# kubectl describe endpoints dnsservices Name: dnsservices Namespace: default Labels: <none> Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2022-01-28T10:24:31Z Subsets: Addresses: 10.244.1.194,10.244.1.195,10.244.2.206 NotReadyAddresses: <none> Ports: Name Port Protocol ---- ---- -------- tcpdns 53 TCP udpdns 53 UDP web 5001 TCP Events: <none> #
可以看到 endpoints Address 已经被更新掉了
