基于K8S的StatefulSet部署MySQL集群

环境：

名称	版本	其他
K8S	1.20.4
mysql	5.7	一主二从
nfs服务器		172.16.201.209

# 采用NFS存储卷的方式 持久化存储mysql数据目录

需求：

展示如何使用 StatefulSet 控制器运行一个有状态的应用程序。此例是多副本的 MySQL 数据库。 示例应用的拓扑结构有一个主服务器和多个副本，使用异步的基于行（Row-Based） 的数据复制。

• 搭建一个“主从复制”（Maser-Slave Replication）的 MySQL 集群
• 存在一个主节点【master】，有多个从节点【slave】
• 从节点可以水平拓展
• 所有的写操作，只能在主节点上执行
• 读操作可以在所有节点上执行

一、部署NFS服务器

#服务器安装nfs服务，提供nfs存储功能
1、安装nfs-utils
yum install nfs-utils (centos)
或者  apt-get install nfs-kernel-server (ubuntu)

2、启动服务
systemctl enable nfs-server
systemctl start nfs-server

3、创建共享目录完成共享配置
mkdir /home/nfs   #创建共享目录

4、编辑共享配置
vim /etc/exports                                           
#语法格式：    共享文件路径     客户机地址（权限）     #这里的客户机地址可以是IP,网段，域名,也可以是任意*
/home/nfs  *(rw,async,no_root_squash)

#服务器安装nfs服务，提供nfs存储功能
1、安装nfs-utils
yum install nfs-utils (centos)
或者  apt-get install nfs-kernel-server (ubuntu)

2、启动服务
systemctl enable nfs-server
systemctl start nfs-server

3、创建共享目录完成共享配置
mkdir /home/nfs   #创建共享目录

4、编辑共享配置
vim /etc/exports                                           
#语法格式：    共享文件路径     客户机地址（权限）     #这里的客户机地址可以是IP,网段，域名,也可以是任意*
/home/nfs  *(rw,async,no_root_squash)

服务自检命令 
exportfs -arv


5、重启服务
systemctl restart nfs-server


6、本机查看nfs 共享目录
#showmount -e 服务器IP地址 (如果提示命令不存在，则需要yum install showmount)

showmount -e 127.0.0.1
/home/nfs *



7、客户端模拟挂载[所有k8s的节点都需要安装客户端]
[root@master-1 ~]# yum install nfs-utils （centos）
或者  apt-get install nfs-common （ubuntu）
[root@master-1 ~]# mkdir /test
[root@master-1 ~]# mount -t nfs 172.16.201.209:/home/nfs /test

#取消挂载
[root@master-1 ~]# umount /test

二、配置PV 动态供给（NFS StorageClass），创建pvc

部署NFS实现自动创建PV插件： 一共设计到4个yaml 文件 ，官方的文档有详细的说明
https://github.com/kubernetes-incubator/external-storage

root@k8s-master1:~ # mkdir  /root/pvc
root@k8s-master1:~ # cd   /root/pvc

• 创建rbac.yaml 文件

root@k8s-master1:pvc # cat rbac.yaml 
kind: ServiceAccount
apiVersion: v1
metadata:
  name: nfs-client-provisioner
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: nfs-client-provisioner-runner
rules:
  - apiGroups: [""]
    resources: ["persistentvolumes"]
    verbs: ["get", "list", "watch", "create", "delete"]
  - apiGroups: [""]
    resources: ["persistentvolumeclaims"]
    verbs: ["get", "list", "watch", "update"]
  - apiGroups: ["storage.k8s.io"]
    resources: ["storageclasses"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create", "update", "patch"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: run-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    namespace: default
roleRef:
  kind: ClusterRole
  name: nfs-client-provisioner-runner
  apiGroup: rbac.authorization.k8s.io
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
rules:
  - apiGroups: [""]
    resources: ["endpoints"]
    verbs: ["get", "list", "watch", "create", "update", "patch"]
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    # replace with namespace where provisioner is deployed
    namespace: default
roleRef:
  kind: Role
  name: leader-locking-nfs-client-provisioner
  apiGroup: rbac.authorization.k8s.io

• 创建deployment.yaml 文件

官方默认的镜像地址，国内可能无法下载，可以使用 image:
fxkjnj/nfs-client-provisioner:latest

#定义NFS 服务器的地址，共享目录名称

root@k8s-master1:pvc # cat deployment.yaml 
apiVersion: v1
kind: ServiceAccount
metadata:
  name: nfs-client-provisioner
---
kind: Deployment
apiVersion: apps/v1 
metadata:
  name: nfs-client-provisioner
spec:
  replicas: 1
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: nfs-client-provisioner
  template:
    metadata:
      labels:
        app: nfs-client-provisioner
    spec:
      serviceAccountName: nfs-client-provisioner
      containers:
        - name: nfs-client-provisioner
          image: fxkjnj/nfs-client-provisioner:latest
          volumeMounts:
            - name: nfs-client-root
              mountPath: /persistentvolumes
          env:
            - name: PROVISIONER_NAME
              value: fuseim.pri/ifs
            - name: NFS_SERVER
              value: 172.16.201.209 
            - name: NFS_PATH
              value: /home/nfs
      volumes:
        - name: nfs-client-root
          nfs:
            server: 172.16.201.209
            path: /home/nfs

• 创建class.yaml

root@k8s-master1:pvc # cat class.yaml 
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: managed-nfs-storage
provisioner: fuseim.pri/ifs # or choose another name, must match deployment's env PROVISIONER_NAME'
parameters:
  archiveOnDelete: "true"

• 部署

root@k8s-master1:pvc # kubectl apply -f .


#查看存储卷
root@k8s-master1:pvc # kubectl  get sc
NAME                  PROVISIONER      RECLAIMPOLICY   VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION   AGE
managed-nfs-storage   fuseim.pri/ifs   Delete          Immediate           false                  25h

三、编写mysql 相关yaml文件

MySQL 示例部署包含一个 ConfigMap、两个 Service 与一个 StatefulSet。

ConfigMap:

vim mysql-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql
  labels:
    app: mysql
data:
  master.cnf: |
    # Apply this config only on the master.
    [mysqld]
    log-bin    
  slave.cnf: |
    # Apply this config only on slaves.
    [mysqld]
    super-read-only

说明：

在这里，我们定义了 master.cnf 和 slave.cnf 两个 MySQL 的配置文件

• master.cnf 开启了log-bin，可以使用二进制日志文件的方式进行主从复制.
• slave.cnf 开启了 super-read-only ，表示从节点只接受主节点的数据同步的所有写的操作，拒绝其他的写入操作，对于用户来说就是只读的
• master.cnf 和 slave.cnf 已配置文件的形式挂载到容器的目录中

Service：

vim mysql-services.yaml

# Headless service for stable DNS entries of StatefulSet members.
apiVersion: v1
kind: Service
metadata:
  name: mysql
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  clusterIP: None
  selector:
    app: mysql
---
# Client service for connecting to any MySQL instance for reads.
# For writes, you must instead connect to the master: mysql-0.mysql.
apiVersion: v1
kind: Service
metadata:
  name: mysql-read
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  selector:
    app: mysql

说明：

clusterIP: None，使用无头服务 Headless Service（相比普通Service只是将spec.clusterIP定义为None，也就是没有clusterIP，直接使用endport 来通信）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: “mysql”字段指定StatefulSet控制器

另外statefulset控制器网络标识，体现在主机名和Pod A记录：

• 主机名：-<编号>

例如: mysql-0

• Pod DNS A记录：. ..svc.cluster.local （POD 之间通过DNS A 记录互相通信）

例如:
mysql-0.mysql.default.svc.cluster.local

StatefulSet:

vim mysql-statefulset.yaml

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  serviceName: mysql
  replicas: 3
  template:
    metadata:
      labels:
        app: mysql
    spec:
      initContainers:
      - name: init-mysql
        image: mysql:5.7
        command:
        - bash
        - "-c"
        - |
          set -ex
          # Generate mysql server-id from pod ordinal index.
          [[ `hostname` =~ -([0-9]+)$ ]] || exit 1
          ordinal=${BASH_REMATCH[1]}
          echo [mysqld] > /mnt/conf.d/server-id.cnf
          # Add an offset to avoid reserved server-id=0 value.
          echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf
          # Copy appropriate conf.d files from config-map to emptyDir.
          if [[ $ordinal -eq 0 ]]; then
            cp /mnt/config-map/master.cnf /mnt/conf.d/
          else
            cp /mnt/config-map/slave.cnf /mnt/conf.d/
          fi          
        volumeMounts:
        - name: conf
          mountPath: /mnt/conf.d
        - name: config-map
          mountPath: /mnt/config-map
      - name: clone-mysql
        image: fxkjnj/xtrabackup:1.0
        command:
        - bash
        - "-c"
        - |
          set -ex
          # Skip the clone if data already exists.
          [[ -d /var/lib/mysql/mysql ]] && exit 0
          # Skip the clone on master (ordinal index 0).
          [[ `hostname` =~ -([0-9]+)$ ]] || exit 1
          ordinal=${BASH_REMATCH[1]}
          [[ $ordinal -eq 0 ]] && exit 0
          # Clone data from previous peer.
          ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql
          # Prepare the backup.
          xtrabackup --prepare --target-dir=/var/lib/mysql          
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
      containers:
      - name: mysql
        image: mysql:5.7
        env:
        - name: MYSQL_ALLOW_EMPTY_PASSWORD
          value: "1"
        ports:
        - name: mysql
          containerPort: 3306
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
        resources:
          requests:
            cpu: 500m
            memory: 1Gi
        livenessProbe:
          exec:
            command: ["mysqladmin", "ping"]
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
        readinessProbe:
          exec:
            # Check we can execute queries over TCP (skip-networking is off).
            command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"]
          initialDelaySeconds: 5
          periodSeconds: 2
          timeoutSeconds: 1
      - name: xtrabackup
        image: fxkjnj/xtrabackup:1.0
        ports:
        - name: xtrabackup
          containerPort: 3307
        command:
        - bash
        - "-c"
        - |
          set -ex
          cd /var/lib/mysql

          # Determine binlog position of cloned data, if any.
          if [[ -f xtrabackup_slave_info && "x$( change_master_to.sql.in
            # Ignore xtrabackup_binlog_info in this case (it's useless).
            rm -f xtrabackup_slave_info xtrabackup_binlog_info
          elif [[ -f xtrabackup_binlog_info ]]; then
            # We're cloning directly from master. Parse binlog position.
            [[ `cat xtrabackup_binlog_info` =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1
            rm -f xtrabackup_binlog_info xtrabackup_slave_info
            echo "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\
                  MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.in
          fi

          # Check if we need to complete a clone by starting replication.
          if [[ -f change_master_to.sql.in ]]; then
            echo "Waiting for mysqld to be ready (accepting connections)"
            until mysql -h 127.0.0.1 -e "SELECT 1"; do sleep 1; done

            echo "Initializing replication from clone position"
            mysql -h 127.0.0.1 \
                  -e "$(

说明：

• 使用xtrbackup 工具进行容器初始化数据的备份，https://www.toutiao.com/i6999565563710292484
• 使用linux 自带的ncat 工具进行容器初始化数据的拷贝[使用ncat指令，远程地从前一个节点拷贝数据到本地] https://www.cnblogs.com/chengd/p/7565280.html
• 使用mysql的binlog 主从复制 来保证主从之间的数据一致
• 利用pod的主机名的序号来判断当前节点为主节点还是从节点，再根据对于节点拷贝不同的配置文件到指定位置
• 使用mysqladmin的ping 作为数据库的健康检测方式
• 使用nfs存储的 PV 动态供给（StorageClass），持久化mysql的数据文件

四、部署并测试

root@k8s-master1:~/kubernetes/mysql# ll
total 24
drwxr-xr-x 2 root root 4096 Nov  3 16:42 ./
drwxr-xr-x 8 root root 4096 Nov  3 13:33 ../
-rw-r--r-- 1 root root  278 Nov  2 22:15 mysql-configmap.yaml
-rw-r--r-- 1 root root  556 Nov  2 22:08 mysql-services.yaml
-rw-r--r-- 1 root root 5917 Nov  3 14:22 mysql-statefulset.yaml

root@k8s-master1:~/kubernetes/mysql# kubectl apply -f .
configmap/mysql create
service/mysql create
service/mysql-read create
statefulset.apps/mysql create


#动态追踪查看Pod的状态：
root@k8s-master1:~/kubernetes/mysql# kubectl get pods -l app=mysql --watch
NAME      READY   STATUS    RESTARTS   AGE
mysql-0   2/2     Running   0          3h12m
mysql-1   2/2     Running   0          3h11m
mysql-2   2/2     Running   0          3h10m

可以看到，StatefulSet 启动成功后，将会有三个 Pod 运行。

接下来，我们可以尝试向这个 MySQL 集群发起请求，执行一些 SQL 操作来验证它是否正常：

kubectl run mysql-client --image=mysql:5.7 -i --rm --restart=Never --\
mysql -h mysql-0.mysql <

如上所示，我们通过启动一个容器，使用 MySQL client 执行了创建数据库和表、以及插入数据的操作。需要注意的是，我们连接的 MySQL 的地址必须是 mysql-0.mysql（即：Master 节点的 DNS A 记录, 因为POD 之间通过DNS A 记录互相通信）只有 Master 节点才能处理写操作。

而通过连接 mysql-read 这个 Service，我们就可以用 SQL 进行读操作，如下所示：

kubectl run mysql-client --image=mysql:5.7 -i -t --rm --restart=Never --\
  mysql -h mysql-read -e "SELECT * FROM test.messages"
  
  
#你应该获得如下输出：
Waiting for pod default/mysql-client to be running, status is Pending, pod ready: false
+---------+
| message |
+---------+
| hello   |
+---------+
pod "mysql-client" deleted

或者：

root@k8s-master1:~/kubernetes/mysql# kubectl run -it --rm --image=mysql:5.7 --restart=Never mysql-client -- mysql -h mysql-read
If you don't see a command prompt, try pressing enter.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7251
Server version: 5.7.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SELECT * FROM test.messages;
+---------+
| message |
+---------+
| hello   |
+---------+
1 row in set (0.00 sec)

mysql> 

2021/11/3 南京 晴

本文参考了以下内容：

https://kubernetes.io/zh/docs/tasks/run-application/run-replicated-stateful-application/

https://www.cnblogs.com/luoahong/p/12857783.html