在kubernetes中运行单节点有状态MySQL应用

参考 / Reference

https://kubernetes.io/docs/ta...

前提需求 / Rquirements

• 现成的kubernetes集群
• 持久存储-PersistentVolume
• 持久存储容量声明-PersistentVolumeClaim

创建yaml文件 / Create YAML file

https://raw.githubusercontent...

分别创建 Service、PersistentVolumeClaim、Deployment

apiVersion: v1
kind: Service
metadata:
  name: mysql
spec:
  ports:
  - port: 3306
  selector:
    app: mysql
  clusterIP: None
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1beta2 # for versions before 1.8.0 use apps/v1beta1
kind: Deployment
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:、
      labels:
        app: mysql
    spec:
      containers:
      - image: mysql:5.6
        name: mysql
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: password
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim

对于PersistentVolumeClaim中Access Modes的解释：

k8s不会真正检查存储的访问模式或根据访问模式做访问限制，只是对真实存储的描述，最终的控制权在真实的存储端。目前支持三种访问模式：

• ReadWriteOnce – PV以read-write 挂载到一个节点
• ReadWriteMany – PV以read-write 方式挂载到多个节点
• ReadOnlyMany – PV以read-only 方式挂载到多个节点

部署YAML文件 / Deploy the Deployment

kubectl create -f https://k8s.io/docs/tasks/run-application/mysql-deployment.yaml
or
kubectl create -f mysql-deployment.yaml

查看Deployment的详细信息

kubectl describe deployment mysql

查看Deployment的pods信息

kubectl get pods -l app=mysql

检查PersistentVolumeClaim的信息

kubectl describe pvc mysql-pv-claim

进入MySQL实例 / Connet to MySQL

启动一个MySQL客户端服务并连接到MySQL

kubectl run -it --rm --image=mysql:5.6 --restart=Never mysql-client -- mysql -h mysql -ppassword

升级MySQL应用 / Upgrade MySQL

可以使用 kubectl apply 命令对Deployment中的image或者其它部分进行升级;

针对有状态应用StatefulSet, 需要注意以下几点:

• Don’t scale the app

This setup is for single-instance apps only. The underlying PersistentVolume can only be mounted to one Pod. For clustered stateful apps, see the StatefulSet documentation.

• Use strategy: type: Recreate

in the Deployment configuration YAML file. This instructs Kubernetes to not use rolling updates. Rolling updates will not work, as you cannot have more than one Pod running at a time. The Recreate strategy will stop the first pod before creating a new one with the updated configuration

删除Deployment / Delete the ployment

Delete the deployed objects by name:

kubectl delete deployment,svc mysql
kubectl delete pvc mysql-pv-claim