运维实战案例容器部分使用Statefulset部署MySQL主从集群

Posted 2021-05-20 洛冰音

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运维实战案例容器部分使用Statefulset部署mysql主从集群

需求分析
解决思路
操作实录与测试流程

需求分析

一主多从模式只能有一个写入端, 多个查询端需要能负载均衡和健康检查
如何保证MASTER端恒定且连接方式不飘逸
解决主从机配置文件不同的问题
每台机器的配置文件中server-id不同, 如何用同一个配置文件模板为所有从机分配各自的配置文件
如何进行数据的持久化

解决思路

根据StatefulSet控制器的特点, 上一个Pod报告就绪后, 才会开始生成下一个Pod, 因此我们可以断定, 第一个就绪的Pod一定是MASTER端, 且如果MASTER端初始化出现问题, 整个后续都不会继续.
根据Headless Service的特点, 首先启动的Pod一定对应的是mysql-0.mysql, 后续会被Pod的DNS自行补全, 因此MASTER端的唯一性和确定性也可以保证
所有Pod又可以放入一个新的svc中管理, 通过ClusterIP实现负载均衡和健康检查
之前我们学过, 在容器创建前依旧会有Init 容器存在, 且顺序执行, 将配置文件的放入和处理操作在Init 容器中执行, 既可以保证容器创建时有符合要求的配置文件, Init 容器本身顺序执行且必须执行完毕的特性也保证了只要逻辑得当, 生成的配置文件一定是符合要求的
两个Service实现读写分离
借助Init 容器实现对配置文件的操作
StatefulSet控制器实现有序建立和定位
PVC动态生成PV来实现数据持久化

参考教程

注意事项

实验采用的设置都不是生产环境下的设置, 并不具备生产环境的安全性
重点在于构建的思路

ConfigMap部分

通过ConfigMap实现将配置模板挂入Pod中的目的

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

可以看到master.cnf和slave.cnf被分别存放, slave.cnf中包括super-read-only参数来实现只读, 这一步是为了提供my.cnf的内容

Service部分

创建读写分离所需要的两个服务
写服务为Headless Service

# 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

无头服务为每个Pod提供一个DNS解析, 因为服务名为 mysql, 所以可以通过在同一 Kubernetes 集群和名字中的任何其他 Pod 内解析 <Pod 名称>.mysql 来访问 Pod, 又因为MASTER端永远第一个被建立, 因此其解析地址永远为mysql-0.mysql

Read相关的服务就是普通的服务, 通过ClusterIP提供负载均衡和健康检查

StatefulSet控制器部分

也是本实验最重要的部分, 可以说以下内容都是通过StatefulSet的特性来实现的

配置文件中server-id的有序递增
Pod创建顺序的有序化
新生成的Pod从上一个Pod复制数据的实现

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 [[ $ordinal -eq 0 ]]; then
            cp /mnt/config-map/master.cnf /mnt/conf.d/
          else
            cp /mnt/config-map/slave.cnf /mnt/conf.d/
          fi          
        volumeMounts:
        - name: conf
          mountPath: /mnt/conf.d
        - name: config-map
          mountPath: /mnt/config-map
      - name: clone-mysql
        image: gcr.io/google-samples/xtrabackup:1.0
        command:
        - bash
        - "-c"
        - |
          set -ex
          # Skip the clone if data already exists.
          [[ -d /var/lib/mysql/mysql ]] && exit 0
          # Skip the clone on master (ordinal index 0).
          [[ `hostname` =~ -([0-9]+)$ ]] || 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: gcr.io/google-samples/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: 10Gi

上面的很长很长的资源清单可以拆分为几个部分来看

第一部分

生成第一个初始化容器: init-mysql, 用MySQL 5.7的镜像作为母盘构建数据库本体服务的容器
采用创建顺序 + 100作为server-id的形式进行配置文件的修改
将conf和config-map两个数据盘挂载进容器

第二部分

生成第二个初始化容器: clone-mysql, 用来进行数据同步, 第一次在带有空PersistentVolume的副本Pod上启动时, 会在从属 Pod 上执行克隆操作.
这意味着它将从另一个运行中的 Pod 复制所有现有数据, 使此其本地状态足够一致, 从而可以开始从主服务器复制.
当新 Pod 作为副本节点加入集合时, 必须假定 MySQL 主节点可能已经有数据. 还必须假设复制日志可能不会一直追溯到时间的开始.
用xtrabackup:1.0的镜像作为母盘构建数据复制的容器
在克隆期间, 源MySQL 服务器性能可能会受到影响. 为了最大程度地减少对 MySQL 主服务器的影响, 该脚本指示每个 Pod从序号较低的 Pod 中克隆, 也就是上一个Pod. 可以这样做的原因是StatefulSet控制器始终确保在启动Pod N + 1之前Pod N已准备就绪.
这个初始化容器使用3307端口进行工作

Init 容器运行完成, 进入主要阶段

第三部分

所以实际上的Pod由提供MySQL服务的MySQL容器和进行辅助的xtrabackup容器组成
xtrabackup容器查看查看克隆的数据文件, 确定是否有必要在副本服务器上初始化MySQL复制
如果需要, 他将等待mysqld准备就绪后复制, 这是用到了上面初始化容器中写好的复制参数
在执行了CHANGE MASTER TO和START SLAVE之后, 数据完成同步
在同步完成后, 其也会自动寻找MASTER端并连接
开始复制后, xtrabackup 容器监听来自其他 Pod的连接, 处理其数据克隆请求. 如果 StatefulSet 扩大规模, 或者下一个 Pod 失去其 PersistentVolumeClaim 并需要重新克隆, 则此服务器将无限期保持运行

至此, 构建步骤完成

操作实录与测试流程

[root@Server2 MySQLStateful]# kubectl get pod -n nfs-client-provisioner 
NAME                                     READY   STATUS    RESTARTS   AGE
nfs-client-provisioner-dbd6bcd94-4h6xh   1/1     Running   1          43h
[root@Server2 MySQLStateful]# systemctl enable --now nfs

[root@Server2 mnt]# cd MySQLStateful/
[root@Server2 MySQLStateful]# kubectl apply -f ConfigMap.yaml 
configmap/mysql created
[root@Server2 MySQLStateful]# kubectl get cm
NAME               DATA   AGE
kube-root-ca.crt   1      3d
mysql              2      33s

[root@Server2 MySQLStateful]# kubectl apply -f Services.yaml 
service/mysql created
service/mysql-read created
[root@Server2 MySQLStateful]# kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP    3d
mysql        ClusterIP   None            <none>        3306/TCP   5s
mysql-read   ClusterIP   10.111.252.35   <none>        3306/TCP   5s

[root@Server2 MySQLStateful]# kubectl apply -f StatefulSet.yaml 
[root@Server2 MySQLStateful]# kubectl get pod
NAME      READY   STATUS     RESTARTS   AGE
mysql-0   2/2     Running    0          28s
mysql-1   2/2     Running    0          19s
mysql-2   0/2     Init:1/2   0          11s
[root@Server2 MySQLStateful]# kubectl get pod
NAME      READY   STATUS    RESTARTS   AGE
mysql-0   2/2     Running   0          2m25s
mysql-1   2/2     Running   0          2m16s
mysql-2   2/2     Running   0          2m8s

##运行测试Pod
[root@Server2 MySQLStateful]# kubectl run demo -it --image=mysql:5.7 -- bash
If you don't see a command prompt, try pressing enter.
root@demo:/# exit
exit
Session ended, resume using 'kubectl attach demo -c demo -i -t' command when the pod is running
[root@Server2 MySQLStateful]# kubectl get pod -o wide
NAME      READY   STATUS    RESTARTS   AGE     IP               NODE      NOMINATED NODE   READINESS GATES
demo      1/1     Running   1          20s     10.244.141.222   server3   <none>           <none>
mysql-0   2/2     Running   0          3m18s   10.244.22.20     server4   <none>           <none>
mysql-1   2/2     Running   0          3m9s    10.244.141.221   server3   <none>           <none>
mysql-2   2/2     Running   0          3m1s    10.244.22.21     server4   <none>           <none>
[root@Server2 MySQLStateful]# kubectl attach demo -it
If you don't see a command prompt, try pressing enter.

##连接Master端进行写入测试
root@demo:/# mysql mysql -h mysql-0.mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \\g.
Your MySQL connection id is 178
Server version: 5.7.30-log MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> show databases;
+------------------------+
| Database               |
+------------------------+
| information_schema     |
| mysql                  |
| performance_schema     |
| sys                    |
| xtrabackup_backupfiles |
+------------------------+
5 rows in set (0.01 sec)

mysql> create database test;
Query OK, 1 row affected (0.02 sec)

mysql> show databases;
+------------------------+
| Database               |
+------------------------+
| information_schema     |
| mysql                  |
| performance_schema     |
| sys                    |
| test                   |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.02 sec)

mysql> exit
Bye

##分别连接其他终端进行读取测试, 测试主从复制情况
root@demo:/# mysql mysql -h mysql-1.mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \\g.
Your MySQL connection id is 195
Server version: 5.7.30 MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> show databases;
+------------------------+
| Database               |
+------------------------+
| information_schema     |
| mysql                  |
| performance_schema     |
| sys                    |
| test                   |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.01 sec)

mysql> show slave status/G;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '/G' at line 1
mysql> show slave status\\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: mysql-0.mysql
                  Master_User: root
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-0-bin.000005
          Read_Master_Log_Pos: 313
               Relay_Log_File: mysql-1-relay-bin.000005
                Relay_Log_Pos: 530
        Relay_Master_Log_File: mysql-0-bin.000005
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           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: 313
              Relay_Log_Space: 907
              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: d9f1bc4f-b463-11eb-80db-9637abf7b267
             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: 
1 row in set (0.00 sec)

ERROR: 
No query specified
mysql> exit
Bye

root@demo:/# mysql mysql -h mysql-2.mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \\g.
Your MySQL connection id is 205
Server version: 5.7.30 MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> show databases;
+------------------------+
| Database               |
+------------------------+
| information_schema     |
| mysql                  |
| performance_schema     |
| sys                    |
| test                   |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.01 sec)

root@demo:/# mysql mysql -h 10.111.252.35
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \\g.
Your MySQL connection id is 276
Server version: 5.7.30 MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> show databases;
+------------------------+
| Database               |
+------------------------+
| information_schema     |
| mysql                  |
| performance_schema     |
| sys                    |
| test                   |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.00 sec)

mysql> exit
Bye
root@demo:/# exit
exit
Session ended, resume using 'kubectl attach demo -c demo -i -t' command when the pod is running

##查看持续化存储情况
[root@Server2 MySQLStateful]# kubectl get pvc
NAME           STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS          AGE
data-mysql-0   Bound    pvc-c25eede4-6e01-4da5-84aa-fc37296570e1   10Gi       RWO            managed-nfs-storage   24m
data-mysql-1   Bound    pvc-d1f574cb-b8e5-4a3e-8f55-695f8dd36797   10Gi       RWO            managed-nfs-storage   23m
data-mysql-2   Bound    pvc-be316432-2b0c-411f-8554-ac32009c042f   10Gi       RWO            managed-nfs-storage   12m
[root@Server2 MySQLStateful]# kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                  STORAGECLASS          REASON   AGE
pvc-be316432-2b0c-411f-8554-ac32009c042f   10Gi       RWO            Delete           Bound    default/data-mysql-2   managed-nfs-storage            12m
pvc-c25eede4-6e01-4da5-84aa-fc37296570e1   10Gi       RWO            Delete           Bound    default/data-mysql-0   managed-nfs-storage            24m
pvc-d1f574cb-b8e5-4a3e-8f55-695f8dd36797   10Gi       RWO            Delete           Bound    default/data-mysql-1   managed-nfs-storage            23m

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需求分析

解决思路

注意事项

ConfigMap部分

Service部分

StatefulSet控制器部分

操作实录与测试流程

运维实战案例容器部分使用Statefulset部署MySQL主从集群

运维实战案例容器部分使用Statefulset部署mysql主从集群