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清单文件

---
apiVersion: v1
kind: Service
metadata:
  name: myapp-svc
  labels:
    app: myapp
    release: stable
spec:
  selector:
    app: myapp
    release: stable
  # 这里要设置为None，不能是""  
  clusterIP: None
  ports:
  - name: myapp
    port: 80
    protocol: TCP
    targetPort: app-port
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deploy
  namespace: default
spec:
  replicas: 3
  revisionHistoryLimit: 3
  selector:
    matchLabels:
      app: myapp
      release: stable
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  template:
    metadata:
      name: myapp-container
      namespace: default
      labels:
        app: myapp
        release: stable
    spec:
      containers:
      - name: myapp-container
        image: ikubernetes/myapp:v1
        ports:
        - name: app-port
          containerPort: 80
          protocol: TCP

获取无头服务信息

# kubectl get svc -o wide
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE       SELECTOR
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   7d        <none>
myapp-svc    ClusterIP   None         <none>        80/TCP    2m        app=myapp,release=stable

获取详细信息

# kubectl describe svc myapp-svc
Name:              myapp-svc
Namespace:         default
Labels:            app=myapp
                   release=stable
Annotations:       kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"app":"myapp","release":"stable"},"name":"myapp-svc","namespace":"default"},...
Selector:          app=myapp,release=stable
Type:              ClusterIP
IP:                None
Port:              myapp  80/TCP
TargetPort:        app-port/TCP
Endpoints:         10.244.1.43:80,10.244.2.132:80,10.244.2.133:80
Session Affinity:  None
Events:            <none>

获取Pods相关信息

# kubectl get pods -o wide
NAME                          READY     STATUS    RESTARTS   AGE       IP             NODE
myapp-deploy-6f96c5bb-d8wkm   1/1       Running   0          12m       10.244.1.43    node002
myapp-deploy-6f96c5bb-mbk46   1/1       Running   0          12m       10.244.2.132   node003
myapp-deploy-6f96c5bb-nz6rf   1/1       Running   0          12m       10.244.2.133   node003

由于是无头服务，也就是没有ClusterIP，所以想要访问就得通过DNS，所以看下DNS解析情况

# dig myapp-svc.default.svc.cluster.local @10.96.0.10 

; <<>> DiG 9.9.4-RedHat-9.9.4-61.el7_5.1 <<>> myapp-svc.default.svc.cluster.local @10.96.0.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4995
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

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

;; ANSWER SECTION:
myapp-svc.default.svc.cluster.local. 5 IN A    10.244.1.43
myapp-svc.default.svc.cluster.local. 5 IN A    10.244.2.132
myapp-svc.default.svc.cluster.local. 5 IN A    10.244.2.133

访问无头服务，由于DNS缓存，所以请求都到一个Pods上了

# kubectl exec -it client-bbf58867f-tzxhf -- /bin/sh
/ # wget -q -O - http://myapp-svc.default.svc.cluster.local/hostname.html
myapp-deploy-6f96c5bb-d8wkm
/ # wget -q -O - http://myapp-svc.default.svc.cluster.local/hostname.html
myapp-deploy-6f96c5bb-d8wkm