前提假设：

1.已安装k8s环境；

2.因为我使用nfs作为pv存储介质，所以需要预先配置好nfs服务

nfs安装可参考：https://blog.csdn.net/wudinaniya/article/details/81068518

步骤：

1.规划mysql持久化文件在nfs中的存储路径；

2.创建mysql pv；

3.创建mysql configmap；

4.创建mysql service；

5.创建mysql statefulset；

6.验证mysql是否安装成功。

步骤1：

在nfs路径下（我是192.168.152.12的/home/nfs/volumes），创建mysql-datadir-1  mysql-datadir-2  mysql-datadir-3三个文件夹

mkdir mysql-datadir-1  mysql-datadir-2  mysql-datadir-3

步骤2：创建pv

pv.yaml:

指向步骤1中的3个mysql-datadir文件夹。 文件中的server填入nfs-server服务所在ip

---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-datadir-1
spec:
  capacity:
    storage: 2Gi
  accessModes: ["ReadWriteMany","ReadWriteOnce"]
  nfs:
    path: /home/nfs/volumes/mysql-datadir-1
    server: 192.168.152.12

---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-datadir-2
spec:
  capacity:
    storage: 2Gi
  accessModes: ["ReadWriteMany","ReadWriteOnce"]
  nfs:
    path: /home/nfs/volumes/mysql-datadir-2
    server: 192.168.152.12

---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-datadir-3
spec:
  capacity:
    storage: 2Gi
  accessModes: ["ReadWriteMany","ReadWriteOnce"]
  nfs:
    path: /home/nfs/volumes/mysql-datadir-3
    server: 192.168.152.12

创建pv

kubectl apply -f pv.yaml

步骤3：创建mysql configmap

configmap.yaml:

apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql
  labels:
    app: mysql
data:
  master.cnf: |
    [mysqld]
    log-bin
    default-time-zone='+8:00'
    log_bin_trust_function_creators=1
    lower_case_table_names=1
  slave.cnf: |
    [mysqld]
    super-read-only
    default-time-zone='+8:00'
    log_bin_trust_function_creators=1

创建configmap

kubectl apply -f configmap.yaml 

步骤4：创建mysql service

service.yaml: 其中服务mysql用于读写；服务mysql-read用于只读。

apiVersion: v1
kind: Service
metadata:
  name: mysql
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  clusterIP: None
  selector:
    app: mysql

---
apiVersion: v1
kind: Service
metadata:
  name: mysql-read
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  selector:
    app: mysql

创建service：

kubectl apply -f service.yaml

步骤5：创建statefulset

statefulset.yaml:

注意事项：官网或其他博客用的xtrabackup镜像无法拉取，所以使用国内阿里云的镜像替代：registry.cn-hangzhou.aliyuncs.com/hxpdocker/xtrabackup:1.0

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 [[ $ordinal -eq 0 ]]; then
            cp /mnt/config-map/master.cnf /mnt/conf.d/
          else
            cp /mnt/config-map/slave.cnf /mnt/conf.d/
          fi
        volumeMounts:
        - name: conf
          mountPath: /mnt/conf.d
        - name: config-map
          mountPath: /mnt/config-map
      - name: clone-mysql
        image: registry.cn-hangzhou.aliyuncs.com/hxpdocker/xtrabackup:1.0
        command:
        - bash
        - "-c"
        - |
          set -ex
          # Skip the clone if data already exists.
          [[ -d /var/lib/mysql/mysql ]] && exit 0
          # Skip the clone on master (ordinal index 0).
          [[ `hostname` =~ -([0-9]+)$ ]] || 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: registry.cn-hangzhou.aliyuncs.com/hxpdocker/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$(<xtrabackup_slave_info)" != "x" ]]; then
            # XtraBackup already generated a partial "CHANGE MASTER TO" query
            # because we're cloning from an existing slave. (Need to remove the tailing semicolon!)
            cat xtrabackup_slave_info | sed -E 's/;$//g' > 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 "$(<change_master_to.sql.in), \
                          MASTER_HOST='mysql-0.mysql', \
                          MASTER_USER='root', \
                          MASTER_PASSWORD='', \
                          MASTER_CONNECT_RETRY=10; \
                        START SLAVE;" || exit 1
            # In case of container restart, attempt this at-most-once.
            mv change_master_to.sql.in change_master_to.sql.orig
          fi

          # Start a server to send backups when requested by peers.
          exec ncat --listen --keep-open --send-only --max-conns=1 3307 -c \
            "xtrabackup --backup --slave-info --stream=xbstream --host=127.0.0.1 --user=root"
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
        resources:
          requests:
            cpu: 100m
            memory: 100Mi
      volumes:
      - name: conf
        emptyDir: {}
      - name: config-map
        configMap:
          name: mysql
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 2Gi

创建statefulset：

kubectl apply -f statefulset.yaml

可以看到，mysql pod正在初始化。因为需要拉取mysql镜像和xtrabackup镜像，所以需要等待

步骤6：验证是否安装成功

6.1查看mysql master状态并创建数据库testdb：

[root@k8s-master mysql]# kubectl exec -it mysql-0 sh

# mysql

mysql> show databases; 

mysql> show master status;

mysql> create database testdb;

mysql> show databases;

6.2 查看其中一个mysql slave的状态，并验证新创建的数据库testdb是否成功同步：

[root@k8s-master mysql-datadir-3]# kubectl exec -it mysql-1 sh

# mysql

mysql> show databases;

查看slave状态：

mysql> show slave status \G;

说明：Slave_IO_State: Waiting for master to send event 证明slave正在监听master

备注：

按照以上步骤，成功完成了基于k8s的mysql5.7主从集群安装。

过程并非顺利，可能会出现slave无法同步数据的问题。但重复安装2次后，问题消失。根因有待继续跟踪

参考链接：

https://blog.51cto.com/u_15127511/2657609

https://blog.csdn.net/weixin_43936969/article/details/106289127

https://www.cnblogs.com/cooper-73/p/12988614.html