k8s之statefulset控制器

operator:

 

statefulset:有状态副本集

特点

运行在: 1,稳定且唯一的网络标识符

2，稳定且持久的存储

3，有序，平滑地部署和扩展

4，有序，平滑地删除和终止

5，有序的滚动更新

 

三个组件:headless service(无头服务), statefuleset,volumeClaimTemplate(存储卷申请模板)

先准备pv

apiVersion: v1

kind: PersistentVolume

metadata:

  name: pv001

  labels:

    name: pv001

    polity: fast

spec:

  nfs:

    path: /data/volumes/v1

    server: node2

  accessModes: ["ReadWriteMany","ReadWriteOnce"]

  capacity:

    storage: 5Gi

---

apiVersion: v1

kind: PersistentVolume

metadata:

  name: pv002

  labels:

    name: pv002

    polity: fast

spec:

  nfs:

    path: /data/volumes/v2

    server: node2

  accessModes: ["ReadWriteOnce"]

  capacity:

    storage: 5Gi

---

 

apiVersion: v1

kind: PersistentVolume

metadata:

  name: pv003

  labels:

    name: pv003

    polity: fast

spec:

  nfs:

    path: /data/volumes/v3

    server: node2

  accessModes: ["ReadWriteMany","ReadWriteOnce"]

  capacity:

    storage: 5Gi

---

 

apiVersion: v1

kind: PersistentVolume

metadata:

  name: pv004

  labels:

    name: pv004

    polity: fast

spec:

  nfs:

    path: /data/volumes/v4

    server: node2

  accessModes: ["ReadWriteMany","ReadWriteOnce"]

  capacity:

    storage: 10Gi

---

 

apiVersion: v1

kind: PersistentVolume

metadata:

  name: pv005

  labels:

    name: pv005

    polity: fast

spec:

  nfs:

    path: /data/volumes/v5

    server: node2

  accessModes: ["ReadWriteMany","ReadWriteOnce"]

  capacity:

    storage: 10Gi

 

 

kubectl apply -f pv-demo.yaml

kubectl get pv

 

 

实例

apiVersion: v1

kind: Service

metadata:

  name: myapp-svc  service名

  labels:

    app: myapp

spec:

  ports:

  - port: 80  service端口

   name: web  service端口名

  clusterIP: None  statefulset要求无头服务

  selector:  与pod关联的标签

    app: myapp-pod

---

apiVersion: apps/v1

kind: StatefulSet

metadata:

  name: myapp  statefulset控制器名 创建的pod名也为这个

spec:

  serviceName: myapp-svc 关联的service服务名，必须是无头服务

  replicas: 2

  selector:  管理哪些pod,关联pod的label

    matchLabels:

      app: myapp-pod

  template: 定义pod模板

    metadata:

      labels:  定义的pod的标签label

        app: myapp-pod

   spec:

     containers:

     - name: myapp  pod中容器名

      image: ikubernetes/myapp:v1

      ports:

      - containerPort: 80

       name: web

      volumeMounts:

       - name: myappdata 挂载myappdata存储卷

         mountPath: /usr/share/nginx/html 容器中挂载的路径

  volumeClaimTemplates:   pvc模板 为每个pod定义volume 自动创建pvc

  - metadata:

      name: myappdata   定义的pvc名

    spec:

      accessModes: ["ReadWriteOnce"]  单路读写

      resources:   资源

        requests: 请求

          storage: 5Gi 大小5Gi存储空间

 

 

创建

kubectl explain sts

kubectl apply -f stateful-demo.yaml

 

 

验证：

kubectl get sts

kubectl get pvc

kubectl get svc

kubectl get pv

kubectl get pods

 

删除sts时

逆向删除pod

kubectl delete -f stateful-demo.yaml

删除时pvc还在，且一直保留给固定的pod

 

statefulset支持滚动更新，规模扩展

逆向更新

 

dns解析

kubectl exec -it myapp-0 -- /bin/sh

nslookup  myapp-3.myapp-svc.default.svc.cluster.local

域名构成   pod名 service名 命名空间 集群域名svc.cluster.local        

域名 pod_name.service_name.namaspace_name.svc.cluster.local

nslookup  myapp-3.myapp-svc

 

 

扩容宿容

kubectl scale sts myapp --replicas=3

kubectl patch sts myapp -p '{"spec":{"replicas":2}}'

 

 

更新策略

kubectl explain sts.spec.updateStrategy

kubectl explain sts.spec.updateStrategy.rollingUpdate

 

 

分区更新

kubectl explain sts.spec.updateStrategy.rollingUpdate.partition

myapp-0

myapp-1

myapp-2

myapp-3

myapp-4

 

partition:N

N>=3

即更新3和4，即myapp-3,myapp-4 这叫金丝雀发布

验证

方法一

kubectl patch sts myapp -p '{"spec":{"replicas":5}}'

kubectl patch sts myapp -p '{"spec":{"updateStrategy":{"rollingUpdate":{"partition":4}}}}' 打上补丁 partition>=4

kubectl describe sts myapp 查看更新策略

kubectl set image sts/myapp myapp=ikubernetes/myapp:v2 改变镜像就会更新了

kubectl get sts -o wide

 

方法二

vim stateful-demo.yaml

kind: StatefulSet

   ...

spec:

  updateStrategy:

    rollingUpdate:

      partition: 3

 

 kubectl apply -f stateful-demo.yaml

 

如果版本没问题，就全部更新

vim stateful-demo.yaml

kind: StatefulSet

   ...

spec:

  updateStrategy:

    rollingUpdate:

      partition: 0

 

kubectl apply -f stateful-demo.yaml