k8s部署mysql主从服务

k8s部署mysql主从服务

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实验环境

kubernetes Master
kubernetes Node (测试演示,所有的副本都会在其上运行)
kubernetes DNS服务已开启

实验目的

搭建一个主从复制(Master-Slave)的MySQL 集群
从节点可以水平扩展
所有的写操作只能在主节点上执行
读操作可以在主从节点上执行
从节点能同步主节点的数据
k8smysql.png

创建Namespace

[root@k8s-master ~]# kubectl create ns mysql
namespace/mysql create

创建ConfigMap为Master/Slave节点分配不同的配置文件

[root@k8s-master mysql]# cat mysql-cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql
  namespace: mysql
  labels:
    app: mysql
data:
  master.cnf: |
    # Master配置
    [mysqld]
    log-bin=mysqllog
    skip-name-resolve
  slave.cnf: |
    # Slave配置
    [mysqld]
    super-read-only
    skip-name-resolve
    log-bin=mysql-bin
    replicate-ignore-db=mysql
[root@k8s-master mysql]# kubectl apply -f mysql-cm.yaml
configmap/mysql created

创建mysql密码Secret

[root@k8s-master mysql]# cat mysql-secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: mysql-secret
  namespace: mysql
  labels:
    app: mysql
type: Opaque
data:
  password: MTIzNDU2 # echo -n "123456" | base64
[root@k8s-master mysql]# kubectl apply -f mysql-secret.yaml
secret/mysql-secret created

创建Service为MySQL提供读写分离

[root@k8s-master mysql]# cat mysql-services.yaml
apiVersion: v1
kind: Service
metadata:
  name: mysql
  namespace: mysql
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  clusterIP: None
  selector:
    app: mysql
---
apiVersion: v1
kind: Service
metadata:
  name: mysql-read
  namespace: mysql
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  selector:
    app: mysql

用户所有写请求,必须以 DNS 记录的方式直接访问到 Master 节点,也就是 mysql-0.mysql 这条 DNS 记录
用户所有读请求,必须访问自动分配的 DNS 记录可以被转发到任意一个 Master 或 Slave 节点上,也就是 mysql-read 这条 DNS 记录

[root@k8s-master mysql]# kubectl apply -f mysql-services.yaml
service/mysql created
service/mysql-read created
[root@k8s-master mysql]# kubectl get -n mysql svc
NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
mysql        ClusterIP   None           <none>        3306/TCP   33s
mysql-read   ClusterIP   10.100.27.49   <none>        3306/TCP   33s

使用StatefulSet搭建MySQL主从集群

[root@k8s-master mysql]# cat mysql-statefulset.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
  namespace: mysql
  labels:
    app: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  serviceName: mysql
  replicas: 2
  template:
    metadata:
      labels:
        app: mysql
    spec:
      initContainers:
      - name: init-mysql
        image: mysql:5.7
        env:
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-secret
              key: password
        command:
        - bash
        - "-c"
        - |
          set -ex
          # 从 Pod 的序号,生成 server-id
          [[ $(hostname) =~ -([0-9]+)$ ]] || exit 1
          ordinal=${BASH_REMATCH[1]}
          echo [mysqld] > /mnt/conf.d/server-id.cnf
          # 由于 server-id 不能为 0,因此给 ID 加 100 来避开它
          echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf
          # 如果 Pod 的序号为 0,说明它是 Master 节点,从 ConfigMap 里把 Master 的配置文件拷贝到 /mnt/conf.d 目录下
          # 否则,拷贝 ConfigMap 里的 Slave 的配置文件
          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: twoeo/gcr.io-google-samples-xtrabackup:latest
        #gcr.io/google-samples/xtrabackup:1.0
        env:
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-secret
              key: password
        command:
        - bash
        - "-c"
        - |
          set -ex
          # 拷贝操作只需要在第一次启动时进行,所以数据已经存在则跳过
          [[ -d /var/lib/mysql/mysql ]] && exit 0
          # Master 节点(序号为 0)不需要这个操作
          [[ $(hostname) =~ -([0-9]+)$ ]] || exit 1
          ordinal=${BASH_REMATCH[1]}
          [[ $ordinal == 0 ]] && exit 0
          # 使用 ncat 指令,远程地从前一个节点拷贝数据到本地
          ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql
          # 执行 --prepare,这样拷贝来的数据就可以用作恢复了
          xtrabackup --prepare --target-dir=/var/lib/mysql
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
      containers:
      - name: mysql
        image: mysql:5.7
        env:
#        - name: MYSQL_ALLOW_EMPTY_PASSWORD
#          value: "1"
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-secret
              key: password
        ports:
        - name: mysql
          containerPort: 3306
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
        resources:
          requests:
            cpu: 500m
            memory: 1Gi
        livenessProbe:
          exec:
            command: ["mysqladmin", "ping", "-uroot", "-p${MYSQL_ROOT_PASSWORD}"]
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
        readinessProbe:
          exec:
            command: ["mysqladmin", "ping", "-uroot", "-p${MYSQL_ROOT_PASSWORD}"]
          initialDelaySeconds: 5
          periodSeconds: 2
          timeoutSeconds: 1
      - name: xtrabackup
        image: twoeo/gcr.io-google-samples-xtrabackup:latest 
        #gcr.io/google-samples/xtrabackup:1.0
        ports:
        - name: xtrabackup
          containerPort: 3307
        env:
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-secret
              key: password
        command:
        - bash
        - "-c"
        - |
          set -ex
          cd /var/lib/mysql
          # 从备份信息文件里读取 MASTER_LOG_FILE 和 MASTER_LOG_POS 这 2 个字段的值,用来拼装集群初始化 SQL
          if [[ -f xtrabackup_slave_info ]]; then
            # 如果 xtrabackup_slave_info 文件存在,说明这个备份数据来自于另一个 Slave 节点
            # 这种情况下,XtraBackup 工具在备份的时候,就已经在这个文件里自动生成了 "CHANGE MASTER TO" SQL 语句
            # 所以,只需要把这个文件重命名为 change_master_to.sql.in,后面直接使用即可
            mv xtrabackup_slave_info change_master_to.sql.in
            # 所以,也就用不着 xtrabackup_binlog_info 了
            rm -f xtrabackup_binlog_info
          elif [[ -f xtrabackup_binlog_info ]]; then
            # 如果只是存在 xtrabackup_binlog_info 文件,说明备份来自于 Master 节点,就需要解析这个备份信息文件,读取所需的两个字段的值
            [[ $(cat xtrabackup_binlog_info) =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1
            rm xtrabackup_binlog_info
            # 把两个字段的值拼装成 SQL,写入 change_master_to.sql.in 文件
            echo "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\
                  MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.in
          fi
          # 如果存在 change_master_to.sql.in,就意味着需要做集群初始化工作
          if [[ -f change_master_to.sql.in ]]; then
            # 但一定要先等 MySQL 容器启动之后才能进行下一步连接 MySQL 的操作
            echo "Waiting for mysqld to be ready(accepting connections)"
            until mysql -h 127.0.0.1 -uroot -p${MYSQL_ROOT_PASSWORD} -e "SELECT 1"; do sleep 1; done
            echo "Initializing replication from clone position"
            # 将文件 change_master_to.sql.in 改个名字
            # 防止这个 Container 重启的时候,因为又找到了 change_master_to.sql.in,从而重复执行一遍初始化流程
            mv change_master_to.sql.in change_master_to.sql.orig
            # 使用 change_master_to.sql.orig 的内容,也就是前面拼装的 SQL,组成一个完整的初始化和启动 Slave 的 SQL 语句
            mysql -h 127.0.0.1 -uroot -p${MYSQL_ROOT_PASSWORD} << EOF
          $(< change_master_to.sql.orig),
            MASTER_HOST='mysql-0.mysql.mysql',
            MASTER_USER='root',
            MASTER_PASSWORD='${MYSQL_ROOT_PASSWORD}',
            MASTER_CONNECT_RETRY=10;
          START SLAVE;
          EOF
          fi
          # 使用 ncat 监听 3307 端口。
          # 它的作用是,在收到传输请求的时候,直接执行 xtrabackup --backup 命令,备份 MySQL 的数据并发送给请求者
          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 --password=${MYSQL_ROOT_PASSWORD}"
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
      volumes:
      - name: conf
        emptyDir: {}
      - name: config-map
        configMap:
          name: mysql
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes:
      - "ReadWriteOnce"
      storageClassName: managed-nfs-storage
      resources:
        requests:
          storage: 5Gi

整体的statefulset有两个replicas,一个Master, 一个Slave,然后使用 init-mysql 这个 initContainers 进行配置文件的初始化。接着使用 clone-mysql 这个 initContainers 进行数据的传输;同时使用 xtrabackup 这个 sidecar 容器进行SQL初始化和数据传输功能
创建 StatefulSet

[root@k8s-master mysql]# kubectl apply -f mysql-statefulset.yaml
[root@k8s-master mysql]# kubectl get po -n mysql
NAME      READY   STATUS    RESTARTS   AGE
mysql-0   2/2     Running   0          17m
mysql-1   2/2     Running   0          16m

可以看到,StatefulSet 启动成功后,会有两个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

验证主从状态

[root@k8s-master mysql]# kubectl -n mysql exec mysql-1 -c mysql -- bash -c "mysql -uroot -p123456 -e 'show slave status \G'"
mysql: [Warning] Using a password on the command line interface can be insecure.
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: mysql-0.mysql.mysql
                  Master_User: root
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysqllog.000003
          Read_Master_Log_Pos: 154
               Relay_Log_File: mysql-1-relay-bin.000002
                Relay_Log_Pos: 319
        Relay_Master_Log_File: mysqllog.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: mysql
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 154
              Relay_Log_Space: 528
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 100
                  Master_UUID: 1662034a-9c35-11ea-a60b-f68f1b10bff0
             Master_Info_File: /var/lib/mysql/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version:

接下来,我们通过Master容器创建数据库和表、插入数据库

[root@k8s-master mysql]# kubectl -n mysql exec mysql-0 -c mysql -- bash -c "mysql -uroot -p123456 -e 'create database test'"
[root@k8s-master mysql]# kubectl -n mysql exec mysql-0 -c mysql -- bash -c "mysql -uroot -p123456 -e 'use test;create table counter(c int);'"
[root@k8s-master mysql]# kubectl -n mysql exec mysql-0 -c mysql -- bash -c "mysql -uroot -p123456 -e 'use test;insert into counter values(123)'"
[root@k8s-master mysql]# kubectl -n mysql exec mysql-0 -c mysql -- bash -c "mysql -uroot -p123456 -e 'use test;select * from counter'"
mysql: [Warning] Using a password on the command line interface can be insecure.
c
123

然后,我们观察Slave节点是否都同步到数据了

[root@k8s-master mysql]# kubectl -n mysql exec mysql-1 -c mysql -- bash -c "mysql -uroot -p123456 -e 'use test;select * from counter'"
mysql: [Warning] Using a password on the command line interface can be insecure.
c
123

当看到输出结果,主从同步正常了

扩展从节点

在有了 StatefulSet 以后,就可以像Deployment那样,非常方便地扩展这个 MySQL 集群,比如

kubectl -n mysql scale statefulset mysql -—replicas=3

$ kubectl get po -n mysql
NAME      READY   STATUS    RESTARTS   AGE
mysql-0   2/2     Running   0          22m
mysql-1   2/2     Running   0          22m
mysql-2   2/2     Running   0          20s

这时候,一个新的mysql-2就创建出来了,我们继续验证新扩容的节点是否都同步到主节点的数据

kubectl -n mysql exec mysql-2 -c mysql -- bash -c "mysql -uroot -p123456 -e 'use test;select * from counter’"  
c
123

当看到输出结果,主从同步正常了。也就是说从 StatefulSet 为我们新创建的 mysql-2 上,同样可以读取到之前插入的记录,也就是说,我们的数据备份和恢复,都是有效的