【深入分析】K8s部署Mysql主从复制+读写分离

痛定思痛。 2023-06-06 08:05 31阅读 0赞

**一、Mysql StatefulSet应用文件预览**  
`已用中文进行解释，请看绿色字体`

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
            imagePullPolicy: IfNotPresent
            command:
            - bash
            - "-c"
            - | set -ex # 从hostname中获取索引，比如(mysql-1)会获取(1) [[ `hostname` =~ -([0-9]+)$ ]] || exit 1 ordinal=${BASH_REMATCH[1]} echo [mysqld] > /mnt/conf.d/server-id.cnf # 为了不让server-id=0而增加偏移量 echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf # 拷贝对应的文件到/mnt/conf.d/文件夹中 if [[ $ordinal -eq 0 ]]; then cp /mnt/config-map/master.cnf /mnt/conf.d/ else cp /mnt/config-map/slave.cnf /mnt/conf.d/ fi
            volumeMounts:
            - name: conf
              mountPath: /mnt/conf.d
            - name: config-map
              mountPath: /mnt/config-map
          - name: clone-mysql
            image: twoeo/gcr.io-google-samples-xtrabackup:latest
            imagePullPolicy: IfNotPresent
            command:
            - bash
            - "-c"
            - | set -ex # 整体意思: # 1.如果是主mysql中的xtrabackup,就不需要克隆自己了,直接退出 # 2.如果是从mysql中的xtrabackup,先判断是否是第一次创建，因为第二次重启本地就有数据库，无需克隆。若是第一次创建(通过/var/lib/mysql/mysql文件是否存在判断),就需要克隆数据库到本地。 # 如果有数据不必克隆数据，直接退出() [[ -d /var/lib/mysql/mysql ]] && exit 0 # 如果是master数据也不必克隆 [[ `hostname` =~ -([0-9]+)$ ]] || exit 1 ordinal=${BASH_REMATCH[1]} [[ $ordinal -eq 0 ]] && exit 0 # 从序列号比自己小一的数据库克隆数据，比如mysql-2会从mysql-1处克隆数据 ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql # 比较数据 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
            imagePullPolicy: IfNotPresent
            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: 50m
                memory: 50Mi
            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: twoeo/gcr.io-google-samples-xtrabackup:latest
            imagePullPolicy: IfNotPresent
            ports:
            - name: xtrabackup
              containerPort: 3307
            command:
            - bash
            - "-c"
            - | set -ex cd /var/lib/mysql # 确定binlog 克隆数据位置(如果binlog存在的话). if [[ -f xtrabackup_slave_info ]]; then # 如果存在该文件，则该xrabackup是从现有的从节点克隆出来的。 mv xtrabackup_slave_info change_master_to.sql.in # 在这种情况下，忽略xtrabackup_binlog_info（它是无用的）。 rm -f xtrabackup_binlog_info elif [[ -f xtrabackup_binlog_info ]]; then # 我们直接从主人那里克隆。分析binlog位置。 [[ `cat xtrabackup_binlog_info` =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1 rm xtrabackup_binlog_info echo "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\ MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.in fi # 检查是否需要通过启动复制来完成克隆. 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" # 如果容器重新启动，最多尝试一次。 mv change_master_to.sql.in change_master_to.sql.orig mysql -h 127.0.0.1 <<EOF $(<change_master_to.sql.orig), MASTER_HOST='mysql-0.mysql', MASTER_USER='root', MASTER_PASSWORD='', MASTER_CONNECT_RETRY=10; START SLAVE; EOF fi # 开启监听服务，发送备份 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: 10m
                memory: 10Mi
          volumes:
          - name: conf
            emptyDir: { }
          - name: config-map
            configMap:
              name: mysql
      volumeClaimTemplates:
      - metadata:
          name: data
        spec:
          accessModes: ["ReadWriteOnce"]
          resources:
            requests:
              storage: 0.1Gi

**1.initContainers作用：**  
(1).主数据库无需同步自己数据，从数据库需要被同步数据  
(2).判断当前启动的容器是主还是slave，并向pod的conf卷写入如下数据

cat /mnt/conf.d/server-id.cnf
    [mysqld]
    server-id=10?
    ls /mnt/conf.d/  
    master[?salve].cnf # 从configmap处拷贝而来

(3)当执行完command命令后生命终止，但是pod的conf卷的数据依然存在，因为初始容器和接下来的container容器使用共同的volumes卷,不同的是conf被initContainer挂载到/mnt/conf.d，而在container被挂载在/etc/mysql/conf.d/  
**2.Container作用：**  
(1)提供mysql服务  
(2)运行xtrabakup应用容器提供数据同步

**二、数据结构分析**

{ 
        "apiVersion":"apps/v1",
        "kind":"StatefulSet",
        "metadata":Object{ ...},
        "spec":{ 
            "selector":Object{ ...},
            "serviceName":"mysql",
            "replicas":3,
            "template":{ 
                "metadata":Object{ ...},
                "spec":{ 
                    "initContainers":Array[2],
                    "containers":Array[2],
                    "volumes":Array[2]
                }
            },
            "volumeClaimTemplates":Array[1]
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4OTAwNTY1_size_16_color_FFFFFF_t_70]  
从上图可知知道satefulSet的pvc模板由pv提供存储，voluems作用范围在Pod内所有容器，volumes卷中conf的数据被所有容器共享，/var/lib/mysql映射的data是要被持久化的数据…

**了解彼此资源、对象的关系后，看这篇文章实现K8s部署Mysql主从复制+读写分离，利用静态存储卷**  
[**【全网最全最详细】Kubernetes部署Mysql主从复制+读写分离**][Kubernetes_Mysql]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4OTAwNTY1_size_16_color_FFFFFF_t_70]: /images/20230601/dd856ccf81184c36ac25b8663cf93357.png
[Kubernetes_Mysql]: https://blog.csdn.net/qq_38900565/article/details/102486100