k8s statefulSet控制器网络标识

k8s-statefulSet控制器-网络标识

1. k8s-statefulSet控制器-网络标识

• 稳定的网络标识：使用Headless Service（相比普通Service只是将spec.clusterIP定义为None）来维护Pod网络身份，会为每个Pod分配一个数字编号并且按照编号顺序部署。还需要在StatefulSet添加serviceName: “nginx” 字段指定StatefulSet控制器要使用这个Headless Service。
• 稳定主要体现在主机名和Pod A记录：
  • 主机名：<statefulset名称>-<编号>
  • Pod DNS A记录：<statefulset名称-编号>. ..svc.cluster.local

1.1 headless service示例

apiVersion: v1
kind: Service
metadata:
  name: web
  namespace: default
spec:
  clusterIP: None       #无头服务
  selector:             #容器选择器
    app: nginx          # 指定关联pod名称
  ports:
    - protocol: TCP    # 协议
      port: 80         # service 端口
      targetPort: 80   # 容器端口
  type: ClusterIP    # 服务类型

1.2 statefulset的pod示例

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  serviceName: "web"  # 绑定的服务
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80
          name: web

1.3 执行命令

• 查询pod创建顺序

  kubectl get pods
  

• 查询主机名

  [root@k8s-master statefulset]# kubectl exec web-0 -- hostname
  web-0
  

• 测试A记录解析

  [root@k8s-master statefulset]# kubectl run -it dns-test --image busybox:1.28.4 /bin/sh
  / # nslookup web.default.svc.cluster.local
  Server:    10.96.0.10
  Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
  
  Name:      web.default.svc.cluster.local
  Address 1: 10.244.107.214 web-2.web.default.svc.cluster.local
  Address 2: 10.244.169.145 web-1.web.default.svc.cluster.local
  Address 3: 10.244.36.88 web-0.web.default.svc.cluster.local
  

2.k8s-案例

• 创建配置目录

  [root@k8s-master yaml]# mkdir -p statefulset
  [root@k8s-master yaml]# cd statefulset/
  

2.1 部署headless service

• 安装headless service服务

  [root@k8s-master statefulset]# vim headless-service.yaml
  [root@k8s-master statefulset]# cat headless-service.yaml 
  apiVersion: v1
  kind: Service
  metadata:
    name: web
    namespace: default
  spec:
    clusterIP: None       #无头服务
    selector:             #容器选择器
      app: nginx          # 指定关联pod名称
    ports:
      - protocol: TCP    # 协议
        port: 80         # service 端口
        targetPort: 80   # 容器端口
    type: ClusterIP    # 服务类型
  
  

• 启动服务

  [root@k8s-master statefulset]# kubectl apply  -f headless-service.yaml 
  service/web created
  

• 查看服务

  [root@k8s-master statefulset]# kubectl get svc
  NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
  kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   17d
  web          ClusterIP   None         <none>        80/TCP    2m44s
  

2.2 部署statefulset的服务

• 编写statefulset_pod服务

  [root@k8s-master statefulset]# vim statefulset_pod.yaml
  [root@k8s-master statefulset]# cat  statefulset_pod.yaml
  apiVersion: apps/v1
  kind: StatefulSet
  metadata:
    name: web
  spec:
    serviceName: "web"  # 绑定的服务
    replicas: 3
    selector:
      matchLabels:
        app: nginx
    template:
      metadata:
        labels:
          app: nginx
      spec:
        containers:
        - name: nginx
          image: nginx
          ports:
          - containerPort: 80
            name: web
  
  

• 启动服务

  [root@k8s-master statefulset]# kubectl apply -f statefulset_pod.yaml 
  statefulset.apps/web created
  

• 验证服务

  [root@k8s-master statefulset]# kubectl get pods
  NAME                                   READY   STATUS    RESTARTS   AGE
  nfs-client-provisioner-95c9579-m2f69   1/1     Running   0          2d4h
  secret-demo-pod                        1/1     Running   0          5d23h
  web-0                                  1/1     Running   0          42s
  web-1                                  1/1     Running   0          37s
  web-2                                  1/1     Running   0          31s
  

3. 验证服务

• 查询pod创建顺序

  [root@k8s-master pv]# kubectl get pods
  NAME                                   READY   STATUS    RESTARTS   AGE
  nfs-client-provisioner-95c9579-qslkg   1/1     Running   0          9m49s
  web-0                                  1/1     Running   0          18h
  web-1                                  1/1     Running   0          18h
  web-2                                  1/1     Running   0          18h
  
  

• 查询主机名

  [root@k8s-master pv]# kubectl exec -it web-0 -- hostname
  web-0
  [root@k8s-master pv]# kubectl exec -it headless-web-0 -- hostname
  headless-web-0
  

• 测试A记录解析

  [root@k8s-master statefulset]# kubectl run -it test --image=busybox:1.28.4 -- /bin/sh
  If you don't see a command prompt, try pressing enter.
  / # nslookup  web
  Server:    10.96.0.10
  Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
  
  Name:      web
  Address 1: 10.244.85.204 web-2.web.default.svc.cluster.local
  Address 2: 10.244.85.203 web-0.web.default.svc.cluster.local
  Address 3: 10.244.58.196 web-1.web.default.svc.cluster.local
  / # nslookup  web-0.web.default.svc.cluster.local
  Server:    10.96.0.10
  Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
  
  Name:      web-0.web.default.svc.cluster.local
  Address 1: 10.244.85.203 web-0.web.default.svc.cluster.local