Kubernetes 部署 MySQL 集群

简介： 在有状态应用中，MySQL是我们最常见也是最常用的。本文我们将实战部署一个一组多从的MySQL集群。

镜像下载、域名解析、时间同步请点击 阿里巴巴开源镜像站

一、配置准备

1. configMap

#application/mysql/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

configMap可以将配置文件和镜像解耦开。
上面的配置意思是，创建一个master.cnf文件配置内容为：log-bin，即开启bin-log日志，供主节点使用。
创建一个slave.cnf文件配置内容为：super-read-only，设为该节点只读，供备用节点使用。

2. service

# application/mysql/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

创建一个服务名为mysql的headless类型的service。
创建一个服务名为mysql-read的service

3. StatefulSet

#application/mysql/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:

      # 设置初始化容器，进行一些准备工作

      initContainers:

      - name: init-mysql

        image: mysql:5.7

        # 为每个MySQL节点配置service-id

        # 如果节点序号是0，则使用master的配置， 其余节点使用slave的配置

        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: gcr.io/google-samples/xtrabackup:1.0

        # 为除了节点序号为0的主节点外的其它节点，备份前一个节点的数据

        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

        # 设置支持免密登录

        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:

          # 设置启动pod需要的资源，官方文档上需要500m cpu，1Gi memory。

          # 我本地测试的时候，会因为资源不足，报1 Insufficient cpu, 1 Insufficient memory错误，所以我改小了点

          requests:

            # m是千分之一的意思，100m表示需要0.1个cpu

            cpu: 100m

            # Mi是兆的意思，需要100M 内存

            memory: 100Mi

        livenessProbe:

          # 使用mysqladmin ping命令，对MySQL节点进行探活检测

          # 在节点部署完30秒后开始，每10秒检测一次，超时时间为5秒

          exec:

            command: ["mysqladmin", "ping"]

          initialDelaySeconds: 30

          periodSeconds: 10

          timeoutSeconds: 5

        readinessProbe:

          # 对节点服务可用性进行检测， 启动5秒后开始，每2秒检测一次，超时时间1秒

          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: gcr.io/google-samples/xtrabackup:1.0

        ports:

        - name: xtrabackup

          containerPort: 3307

        # 开始进行备份文件校验、解析和开始同步

        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

  # 设置PVC

  volumeClaimTemplates:

  - metadata:

      name: data

    spec:

      accessModes: ["ReadWriteOnce"]

      resources:

        requests:

          storage: 1Gi

主从节点的配置和启动都在上面的yaml文件中定义好了，接下来需要逐个创建即可。

二、创建所需资源

//创建configMap

kubectl apply -f configMap.yaml

//创建service

kubectl apply -f service.yaml

//创建statefulSet

kubectl apply -f statefulSet.yaml

执行完毕后可以使用以下命令监测创建情况。

kubectl get pods --watch

三、测试主库

1. 进入pod进行操作

进入到pod mysql-0中，进行测试

kubectl exec -it mysql-0 bash

2. 用mysql-client链接mysql-0

mysql -h mysql-0

3. 创建库、表

//创建数据库test

create database test;

//使用test库

use test;

//创建message表

create table message (message varchar(50));

//查看message表结构

show create table message;

4. 插入数据

//插入

insert into message value("hello aloofjr");

//查看

select * from message;

四、测试备库

1. 连接mysql-1

mysql -h mysql-1.mysql

2. 查看库、表结构

//查看数据库列表

show databases;

//使用test库

use test;

//查看表列表

show tables;

//查看message表结构

show create table message;

3. 读取数据

//查看

select * from message;

4. 写入数据

insert into message values("hello world");

此时会报错 ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement
这是因为mysql-1是一个只读备库，无法进行写操作。

五、测试mysql-read服务

kubectl run mysql-client-loop --image=mysql:5.7 -i -t --rm --restart=Never --\

  bash -ic "while sleep 1; do mysql -h mysql-read -e 'SELECT @@server_id,NOW()'; done"

每秒查询一次数据库，可以观察到，调度到不同的server-id，即pod节点

六、扩缩容

//扩容至5副本

kubectl scale statefulset mysql  --replicas=5

//缩容只2副本

kubectl scale statefulset mysql  --replicas=2

七、清理

kubectl delete statefulset mysql

kubectl delete configmap,service,pvc -l app=mysql

八、总结

上面就是通过k8s部署一个一主多从mysql集群的过程，其中有几个重要知识点：

• 通过configMap可以将配置和镜像解耦
• 通过initContainers在pod启动前，做一些初始化工作
• 通过requests设置pod所需的cpu和memory
• 通过livenessProbe进行pod节点探活
• 通过readnessProbe进行pod可用性检测

本文中用到的yaml文件见我的GitHub仓库AloofJr

本文转自： Kubernetes 部署 MySQL 集群-阿里云开发者社区