Service
K8S Service可以简单理解为逻辑上的一组Pod。一种可以访问Pod的策略，其他Pod可以通过这个Service访问到这个Service代理的Pod。
相对于Pod而言，它会有一个固定的名称，一旦创建就固定不变。可以简单的理解成访问一个或者一组Pod的时候，先去访问Service,然后再去访问的IP,Service的名称的固定的，不管Pod是否更新或者重启，都不影响用户的使用
启动 nginx
[root@master01 ~]#
[root@master01 ~]# kubectl get po -owide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
busybox 1/1 Running 4 5d23h 172.18.71.31 master03 <none> <none>
nginx-deployment-5787596d54-6ffh4 1/1 Running 1 24h 172.18.71.30 master03 <none> <none>
nginx-deployment-5787596d54-7m47n 1/1 Running 1 24h 172.31.112.157 master01 <none> <none>
nginx-deployment-5787596d54-cnjb8 1/1 Running 1 24h 172.21.231.156 node02 <none> <none>
</none></none></none></none></none></none></none></none>
可以通过Pod IP 访问
[root@master01 ~]# curl 172.31.112.157
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
存在的问题
Pod 一旦更新Ip就会发生变化
[root@master01 deployment]# kubectl get po -owide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
busybox 1/1 Running 4 5d23h 172.18.71.31 master03 <none> <none>
nginx-deployment-559d658b74-4td67 1/1 Running 0 12s 172.31.112.159 master01 <none> <none>
nginx-deployment-559d658b74-nkb72 1/1 Running 0 16s 172.31.112.158 master01 <none> <none>
nginx-deployment-559d658b74-stql7 1/1 Running 0 14s 172.20.59.219 master02 <none> <none>
[root@master01 deployment]# kubectl edit deployment nginx-deployment
deployment.apps/nginx-deployment edited
[root@master01 deployment]# kubectl get po -owide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
busybox 1/1 Running 4 6d 172.18.71.31 master03 <none> <none>
nginx-deployment-5787596d54-7564h 1/1 Running 0 13m 172.31.112.160 master01 <none> <none>
nginx-deployment-5787596d54-76txc 1/1 Running 0 13m 172.21.231.158 node02 <none> <none>
nginx-deployment-5787596d54-j77s9 1/1 Running 0 13m 172.18.71.32 master03 <none> <none>
</none></none></none></none></none></none></none></none></none></none></none></none></none></none></none></none>
通过 Service 可以这一层抽象，当Pod IP发生变化时，客户端是无感的。
Service 创建的时候,k8s 会创建一个同名的 endpoint, endpoint 记录的就是 Pod 的ip
[root@master01 deployment]# kubectl get svc -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP,9153/TCP 14d
metrics-server ClusterIP 10.109.10.62 <none> 443/TCP 14d
[root@master01 deployment]# kubectl get ep -n kube-system
NAME ENDPOINTS AGE
kube-dns 172.29.55.27:53,172.29.55.27:53,172.29.55.27:9153 14d
metrics-server 172.21.231.157:4443 14d
[root@master01 deployment]# kubectl get po -n kube-system -owide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
calico-kube-controllers-5f6d4b864b-k45q5 1/1 Running 10 14d 192.168.44.13 node01 <none> <none>
calico-node-58hbg 1/1 Running 10 14d 192.168.44.12 master03 <none> <none>
calico-node-dlj65 1/1 Running 10 14d 192.168.44.11 master02 <none> <none>
calico-node-jqb6h 1/1 Running 10 14d 192.168.44.14 node02 <none> <none>
calico-node-r8fl5 1/1 Running 11 14d 192.168.44.10 master01 <none> <none>
calico-node-wv4vx 1/1 Running 10 14d 192.168.44.13 node01 <none> <none>
coredns-867d46bfc6-ljdjr 1/1 Running 10 14d 172.29.55.27 node01 <none> <none>
metrics-server-595f65d8d5-6k4wq 1/1 Running 18 14d 172.21.231.157 node02 <none> <none>
</none></none></none></none></none></none></none></none></none></none></none></none></none></none></none></none></none></none>
`
apiVersion: v1
kind: Pod
metadata:
name: nginx
labels:
app.kubernetes.io/name: proxy
spec:
containers:
– name: nginx
image: nginx:stable
ports:
– containerPort: 80
name: http-web-svc
Original: https://www.cnblogs.com/arvinhuang/p/16871865.html
Author: 平凡键客
Title: Kubernetes Service 笔记
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