【容器应用系列教程】Kubernetes有状态负载StatefulSet

一、StatefulSet介绍

• 本质上就是POD
• 特性
  • 重建POD时，会自动挂载之前的数据卷
  • 依赖于网络存储的数据卷
• 适用场景：适用于数据库

二、创建StatefulSet

1.创建PV和PVC

创建过程省略
关于PV和PVC的创建教程：https://www.wsjj.top/archives/144

[root@k8s-master opt]# kubectl get pv -n default
NAME      CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM              STORAGECLASS   REASON   AGE
nfs-pv1   1900M      RWX            Recycle          Available                                              15h
nfs-pv2   4G         RWX            Recycle          Bound       default/test-pvc                           15h

[root@k8s-master opt]# kubectl get pvc -n default
NAME       STATUS   VOLUME    CAPACITY   ACCESS MODES   STORAGECLASS   AGE
test-pvc   Bound    nfs-pv2   4G         RWX                           14h

2.创建有状态负载StatefulSet

[root@k8s-master opt]# vim state-mysql.yml

apiVersion: apps/v1
kind: StatefulSet	#类型为有状态负载
metadata:
    name: mysql
spec:
    replicas: 1
    selector:
         matchLabels:
             app: mysql
    serviceName: "mysql"	#此处需要绑定服务名，这个服务名对应着下面的Service
    template:
       metadata:
           labels:
              app: mysql
       spec:
           containers:
           - name: mysql
             image: mysql:5.7
             imagePullPolicy: IfNotPresent
             env:
             - name: MYSQL_ROOT_PASSWORD
               value: redhat
             volumeMounts:
               - name: mysql-volume
                 mountPath: /var/lib/mysql	#配置永久挂载数据目录
           volumes:
             - name: mysql-volume	#创建个数据卷
               persistentVolumeClaim:	#挂载PVC
                    claimName: test-pvc
---
apiVersion: v1
kind: Service
metadata:
    name: mysql
spec:
    ports:
    - port: 3306
    selector:
        app: mysql

[root@k8s-master opt]# kubectl get pods -n default
NAME      READY   STATUS    RESTARTS   AGE
mysql-0   1/1     Running   0          153m

进入数据库创建测试数据

[root@k8s-master opt]# kubectl exec -it mysql-0 -n default -- bash
bash-4.2# mysql -uroot -predhat
mysql> create database AAA;
Query OK, 1 row affected (0.01 sec)

mysql> create database BBB;
Query OK, 1 row affected (0.00 sec)

mysql> create database CCC;
Query OK, 1 row affected (0.01 sec)

查看NFS共享目录

[root@k8s-nfs ~]# ls /data2
auto.cnf         ib_buffer_pool  mysql               server-cert.pem
ca-key.pem       ibdata1         mysql.sock          server-key.pem
ca.pem           ib_logfile0     performance_schema  sys
client-cert.pem  ib_logfile1     private_key.pem
client-key.pem   ibtmp1          public_key.pem

删除Pod模拟故障

[root@k8s-master opt]# kubectl delete pod mysql-0 -n default
pod "mysql-0" deleted

Pod会自动创建

并且名字和被删除的Pod名字一样

[root@k8s-master ~]# kubectl get pods -n default
NAME      READY   STATUS        RESTARTS   AGE
mysql-0   0/1     Terminating   0          155m

[root@k8s-master ~]# kubectl get pods -n default
NAME      READY   STATUS              RESTARTS   AGE
mysql-0   0/1     ContainerCreating   0          1s

[root@k8s-master ~]# kubectl get pods -n default
NAME      READY   STATUS    RESTARTS   AGE
mysql-0   1/1     Running   0          2s

再次查看NFS共享目录

文件没有丢失

[root@k8s-nfs ~]# ls /data2
auto.cnf         ib_buffer_pool  mysql               server-cert.pem
ca-key.pem       ibdata1         mysql.sock          server-key.pem
ca.pem           ib_logfile0     performance_schema  sys
client-cert.pem  ib_logfile1     private_key.pem
client-key.pem   ibtmp1          public_key.pem

登录数据库查看库

刚才创建的库还存在

[root@k8s-master opt]# kubectl exec -it mysql-0 -n default -- bash
bash-4.2# mysql -uroot -predhat

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| AAA                |
| BBB                |
| CCC                |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
7 rows in set (0.01 sec)