Fsl's Markdown site

Appearance

Headless服务 ​

实验manifest ​

busybox ​

yaml
apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: test-es
spec:
  containers:
  - image: busybox
    command:
      - sleep
      - "360000"
    imagePullPolicy: IfNotPresent
    name: busybox

StatefulSet ​

yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
  namespace: test-es
spec:
  podManagementPolicy: Parallel
  selector:
    matchLabels:
      app: nginx
  serviceName: ng-svc-headless
  replicas: 3
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1
        ports:
        - containerPort: 80
          name: web

deploy ​

yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: ng-deployment
  namespace: test-es
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1
        ports:
        - containerPort: 80

SVC-clusterIP ​

yaml
apiVersion: v1
kind: Service
metadata:
  namespace: test-es
  name: ng-svc
  labels:
    app: nginx-svc
spec:
  ports:
  - port: 80
    name: web
  selector:
    app: nginx-pod

SVC-Headless ​

yaml
apiVersion: v1
kind: Service
metadata:
  namespace: test-es
  name: ng-svc-headless
  labels:
    app: nginx-svc
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx-pod

结论 ​

headless与clusterIP区别在于,当向clusterIP发起请求时,kube-proxy,一个clusterIP,然后通过这个clusterIP向后端负载均衡 而Headless确实不走kube-proxy,直接由dns返回后端pod的IP 而且在StatefulSet中可以通过域名访问到每一个pod

过程 ​

将以上manifest应用一下,在此名称空间下,找到一个可以curl和ping的pod, 在进行实验时,需要修改每个pod下/usr/share/nginx/html/index.html,将其修改为具有标识性的内容

shell
[elasticsearch@test-master-0 ~]$ curl ng-svc
2
[elasticsearch@test-master-0 ~]$ curl ng-svc
1
[elasticsearch@test-master-0 ~]$ curl ng-svc
3

先对clusterIP进行访问,可以访问得到

shell
[elasticsearch@test-master-0 ~]$ curl ng-svc-headless
1
[elasticsearch@test-master-0 ~]$ curl ng-svc-headless
2
[elasticsearch@test-master-0 ~]$ curl ng-svc-headless
3

再对headless进行访问,也可以访问得到

shell
lasticsearch@test-master-0 ~]$ ping ng-svc-headless
PING ng-svc-headless.test-es.svc.cluster.local (10.42.248.158) 56(84) bytes of data.
64 bytes from 10-42-248-158.ng-svc.test-es.svc.cluster.local (10.42.248.158): icmp_seq=1 ttl=62 time=0.337 ms
[elasticsearch@test-master-0 ~]$ ping ng-svc-headless
PING ng-svc-headless.test-es.svc.cluster.local (10.42.20.6) 56(84) bytes of data.
64 bytes from 10-42-20-6.ng-svc.test-es.svc.cluster.local (10.42.20.6): icmp_seq=1 ttl=62 time=0.463 ms
[elasticsearch@test-master-0 ~]$ ping ng-svc-headless
PING ng-svc-headless.test-es.svc.cluster.local (10.42.160.180) 56(84) bytes of data.
64 bytes from 10-42-160-180.ng-svc.test-es.svc.cluster.local (10.42.160.180): icmp_seq=1 ttl=62 time=0.259 ms

对headless进行ping,可以得到后端的IP

shell
[elasticsearch@test-master-0 ~]$ ping ng-svc
PING ng-svc.test-es.svc.cluster.local (10.43.12.65) 56(84) bytes of data.

对Cluster进行访问,可以得到ClusterIP而无法得到后端podIP

shell
[root@cq49 ~]# kubectl get svc -n test-es ng-svc
NAME     TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)   AGE
ng-svc   ClusterIP   10.43.12.65   <none>        80/TCP    21m

StatefulSet ​

在进行实验时,需要修改每个pod下/usr/share/nginx/html/index.html,将其修改为具有标识性的内容

这样就可以通过域名来对应一个个的pod,如果在他们sts内部,还可以不使用svcName,直接使用podName去访问pod

shell
[elasticsearch@test-master-0 ~]$ curl ng-sts-0.ng-svc-headless
1
[elasticsearch@test-master-0 ~]$ curl ng-sts-1.ng-svc-headless
2
[elasticsearch@test-master-0 ~]$ curl ng-sts-2.ng-svc-headless
3