[root@k8s-master mainfests]# cat redis-svc.yaml 
apiVersion: v1
kind: Service
metadata:
  name: redis
  namespace: default
spec:
  selector:　　#標簽選擇器，必須指(zhi)定pod資源本身的標簽
    app: redis
    role: logstor
  type: ClusterIP　　#指定服務類型為ClusterIP
  ports: 　　#指定端口
  - port: 6379　　#暴露給服務的端口
  - targetPort: 6379　　#容器的端口
[root@k8s-master mainfests]# kubectl apply -f redis-svc.yaml 
service/redis created
[root@k8s-master mainfests]# kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
kubernetes   ClusterIP   10.96.0.1        <none>        443/TCP    36d
redis        ClusterIP   10.107.238.182   <none>        6379/TCP   1m

[root@k8s-master mainfests]# kubectl describe svc redis
Name:              redis
Namespace:         default
Labels:            <none>
Annotations:       kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"name":"redis","namespace":"default"},"spec":{"ports":[{"port":6379,"targetPort":6379}...
Selector:          app=redis,role=logstor
Type:              ClusterIP
IP:                10.107.238.182　　#service ip
Port:              <unset>  6379/TCP
TargetPort:        6379/TCP
Endpoints:         10.244.1.16:6379　　#此處的ip+端口就是pod的ip+端口
Session Affinity:  None
Events:            <none>

[root@k8s-master mainfests]# kubectl get pod redis-5b5d6fbbbd-v82pw -o wide
NAME                     READY     STATUS    RESTARTS   AGE       IP            NODE
redis-5b5d6fbbbd-v82pw   1/1       Running   0          20d       10.244.1.16   k8s-node01

[root@k8s-master mainfests]# kubectl get pods --show-labels |grep myapp-deploy
myapp-deploy-69b47bc96d-4hxxw   1/1       Running   0          12m       app=myapp,pod-template-hash=2560367528,release=canary
myapp-deploy-69b47bc96d-95bc4   1/1       Running   0          12m       app=myapp,pod-template-hash=2560367528,release=canary
myapp-deploy-69b47bc96d-hwbzt   1/1       Running   0          12m       app=myapp,pod-template-hash=2560367528,release=canary
myapp-deploy-69b47bc96d-pjv74   1/1       Running   0          12m       app=myapp,pod-template-hash=2560367528,release=canary
myapp-deploy-69b47bc96d-rf7bs   1/1       Running   0          12m       app=myapp,pod-template-hash=2560367528,release=canary

[root@k8s-master mainfests]# cat myapp-svc.yaml #為myapp創建service
apiVersion: v1
kind: Service
metadata:
  name: myapp
  namespace: default
spec:
  selector:
    app: myapp
    release: canary
  type: NodePort
  ports: 
  - port: 80
    targetPort: 80
    nodePort: 30080
[root@k8s-master mainfests]# kubectl apply -f myapp-svc.yaml 
service/myapp created
[root@k8s-master mainfests]# kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
kubernetes   ClusterIP   10.96.0.1        <none>        443/TCP        36d
myapp        NodePort    10.101.245.119   <none>        80:30080/TCP   5s
redis        ClusterIP   10.107.238.182   <none>        6379/TCP       28m

[root@k8s-master mainfests]# while true;do curl http://192.168.56.11:30080/hostname.html;sleep 1;done
myapp-deploy-69b47bc96d-95bc4
myapp-deploy-69b47bc96d-4hxxw
myapp-deploy-69b47bc96d-pjv74
myapp-deploy-69b47bc96d-rf7bs
myapp-deploy-69b47bc96d-95bc4
myapp-deploy-69b47bc96d-rf7bs
myapp-deploy-69b47bc96d-95bc4
myapp-deploy-69b47bc96d-pjv74
myapp-deploy-69b47bc96d-4hxxw
myapp-deploy-69b47bc96d-pjv74
myapp-deploy-69b47bc96d-pjv74
myapp-deploy-69b47bc96d-4hxxw
myapp-deploy-69b47bc96d-pjv74
myapp-deploy-69b47bc96d-pjv74
myapp-deploy-69b47bc96d-pjv74
myapp-deploy-69b47bc96d-95bc4
myapp-deploy-69b47bc96d-hwbzt

[root@k8s-master mainfests]# while true;do curl //192.168.56.11:30080/;sleep 1;done

  Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
  Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
  Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
  Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
  Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
  Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name<;/a>

[root@k8s-master mainfests]# kubectl explain svc.spec.sessionAffinity
KIND:     Service
VERSION:  v1

FIELD:    sessionAffinity <string>

DESCRIPTION:
     Supports "ClientIP" and "None". Used to maintain session affinity. Enable
     client IP based session affinity. Must be ClientIP or None. Defaults to
     None. More info:
     https://kubernetes.io/docs/concepts/services-networking/service/#virtual-ips-and-service-proxies

[root@k8s-master mainfests]# vim myapp-svc.yaml 
apiVersion: v1
kind: Service
metadata:
  name: myapp
  namespace: default
spec:
  selector:
    app: myapp
    release: canary
  sessionAffinity: ClientIP
  type: NodePort
  ports: 
  - port: 80
    targetPort: 80
    nodePort: 30080
[root@k8s-master mainfests]# kubectl apply -f myapp-svc.yaml 
service/myapp configured
[root@k8s-master mainfests]# kubectl describe svc myapp
Name:                     myapp
Namespace:                default
Labels:                   <none>
Annotations:              kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"name":"myapp","namespace":"default"},"spec":{"ports":[{"nodePort":30080,"port":80,"ta...
Selector:                 app=myapp,release=canary
Type:                     NodePort
IP:                       10.101.245.119
Port:                     <unset>  80/TCP
TargetPort:               80/TCP
NodePort:                 <unset>  30080/TCP
Endpoints:                10.244.1.18:80,10.244.1.19:80,10.244.2.15:80 + 2 more...
Session Affinity:         ClientIP
External Traffic Policy:  Cluster
Events:                   <none>
[root@k8s-master mainfests]# while true;do curl http://192.168.56.11:30080/hostname.html;sleep 1;done
myapp-deploy-69b47bc96d-hwbzt
myapp-deploy-69b47bc96d-hwbzt
myapp-deploy-69b47bc96d-hwbzt
myapp-deploy-69b47bc96d-hwbzt
myapp-deploy-69b47bc96d-hwbzt
myapp-deploy-69b47bc96d-hwbzt
myapp-deploy-69b47bc96d-hwbzt
myapp-deploy-69b47bc96d-hwbzt

kubectl patch svc myapp -p '{"spec":{"sessionAffinity":"ClusterIP"}}'  #session保持，同一ip訪問同一個pod

kubectl patch svc myapp -p '{"spec":{"sessionAffinity":"None"}}'    #取消session 

（1）編寫headless service配置清單
[root@k8s-master mainfests]# cp myapp-svc.yaml myapp-svc-headless.yaml 
[root@k8s-master mainfests]# vim myapp-svc-headless.yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-headless
  namespace: default
spec:
  selector:
    app: myapp
    release: canary
  clusterIP: "None"　　#headless的clusterIP值為None
  ports: 
  - port: 80
    targetPort: 80

（2）創建headless service 
[root@k8s-master mainfests]# kubectl apply -f myapp-svc-headless.yaml 
service/myapp-headless created
[root@k8s-master mainfests]# kubectl get svc
NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
kubernetes       ClusterIP   10.96.0.1        <none>        443/TCP        36d
myapp            NodePort    10.101.245.119   <none>        80:30080/TCP   1h
myapp-headless   ClusterIP   None             <none>        80/TCP         5s
redis            ClusterIP   10.107.238.182   <none>        6379/TCP       2h

（3）使用coredns進行解析驗證
[root@k8s-master mainfests]# dig -t A myapp-headless.default.svc.cluster.local. @10.96.0.10

; <<>> DiG 9.9.4-RedHat-9.9.4-61.el7 <<>> -t A myapp-headless.default.svc.cluster.local. @10.96.0.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62028
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;myapp-headless.default.svc.cluster.local. IN A

;; ANSWER SECTION:
myapp-headless.default.svc.cluster.local. 5 IN A 10.244.1.18
myapp-headless.default.svc.cluster.local. 5 IN A 10.244.1.19
myapp-headless.default.svc.cluster.local. 5 IN A 10.244.2.15
myapp-headless.default.svc.cluster.local. 5 IN A 10.244.2.16
myapp-headless.default.svc.cluster.local. 5 IN A 10.244.2.17

;; Query time: 4 msec
;; SERVER: 10.96.0.10#53(10.96.0.10)
;; WHEN: Thu Sep 27 04:27:15 EDT 2018
;; MSG SIZE  rcvd: 349

[root@k8s-master mainfests]# 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   36d

[root@k8s-master mainfests]# kubectl get pods -o wide -l app=myapp
NAME                            READY     STATUS    RESTARTS   AGE       IP            NODE
myapp-deploy-69b47bc96d-4hxxw   1/1       Running   0          1h        10.244.1.18   k8s-node01
myapp-deploy-69b47bc96d-95bc4   1/1       Running   0          1h        10.244.2.16   k8s-node02
myapp-deploy-69b47bc96d-hwbzt   1/1       Running   0          1h        10.244.1.19   k8s-node01
myapp-deploy-69b47bc96d-pjv74   1/1       Running   0          1h        10.244.2.15   k8s-node02
myapp-deploy-69b47bc96d-rf7bs   1/1       Running   0          1h        10.244.2.17   k8s-node02

（4）對比含有ClusterIP的service解析
[root@k8s-master mainfests]# dig -t A myapp.default.svc.cluster.local. @10.96.0.10

; <<>> DiG 9.9.4-RedHat-9.9.4-61.el7 <<>> -t A myapp.default.svc.cluster.local. @10.96.0.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50445
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;myapp.default.svc.cluster.local. IN    A

;; ANSWER SECTION:
myapp.default.svc.cluster.local. 5 IN    A    10.101.245.119

;; Query time: 1 msec
;; SERVER: 10.96.0.10#53(10.96.0.10)
;; WHEN: Thu Sep 27 04:31:16 EDT 2018
;; MSG SIZE  rcvd: 107

[root@k8s-master mainfests]# kubectl get svc
NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
kubernetes       ClusterIP   10.96.0.1        <none>        443/TCP        36d
myapp            NodePort    10.101.245.119   <none>        80:30080/TCP   1h
myapp-headless   ClusterIP   None             <none>        80/TCP         11m
redis            ClusterIP   10.107.238.182   <none>        6379/TCP       2h