关于mysql:5-MGR管理维护-深入浅出MGR

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明天介绍 MGR 集群的日常治理保护操作,包含主节点切换,单主 & 多主模式切换等。手工操作以及利用 MySQL Shell 两种形式都会别离介绍。

当初有个三节点的 MGR 集群:

mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST  | MEMBER_PORT | MEMBER_STATE | MEMBER_ROLE | MEMBER_VERSION |
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+
| group_replication_applier | af39db70-6850-11ec-94c9-00155d064000 | 172.16.16.10 |        3306 | ONLINE       | PRIMARY     | 8.0.25         |
| group_replication_applier | b05c0838-6850-11ec-a06b-00155d064000 | 172.16.16.11 |        3306 | ONLINE       | SECONDARY   | 8.0.25         |
| group_replication_applier | b0f86046-6850-11ec-92fe-00155d064000 | 172.16.16.12 |        3306 | ONLINE       | SECONDARY   | 8.0.25         |
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+

1. 切换主节点

当主节点须要进行保护时,或者执行滚动降级时,就能够对其进行切换,将主节点切换到其余节点。

在命令行模式下,能够应用 group_replication_set_as_primary() 这个 udf 实现切换,例如:

-- 将 Primary 角色切换到第二个节点
mysql> select group_replication_set_as_primary('b05c0838-6850-11ec-a06b-00155d064000');
+--------------------------------------------------------------------------+
| group_replication_set_as_primary('b05c0838-6850-11ec-a06b-00155d064000') |
+--------------------------------------------------------------------------+
| Primary server switched to: b05c0838-6850-11ec-a06b-00155d064000         |
+--------------------------------------------------------------------------+
1 row in set (1.00 sec)

[root@yejr.run:mysql.sock] [(none)]>select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST  | MEMBER_PORT | MEMBER_STATE | MEMBER_ROLE | MEMBER_VERSION |
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+
| group_replication_applier | af39db70-6850-11ec-94c9-00155d064000 | 172.16.16.10 |        3306 | ONLINE       | SECONDARY   | 8.0.25         |
| group_replication_applier | b05c0838-6850-11ec-a06b-00155d064000 | 172.16.16.11 |        3306 | ONLINE       | PRIMARY     | 8.0.25         |
| group_replication_applier | b0f86046-6850-11ec-92fe-00155d064000 | 172.16.16.12 |        3306 | ONLINE       | SECONDARY   | 8.0.25         |
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+

顺便提一下,在 MySQL 5.7 版本中,只能通过重启以实现主节点的主动切换,不能手动切换。从这个角度来说,如果想要应用 MGR,最好是抉择 MySQL 8.0 版本,而不要应用 5.7 版本。

如果是用 MySQL Shell,则能够调用 setPrimaryInstance() 函数进行切换:

# 首先获取 cluster 对象
 MySQL  172.16.16.10:3306 ssl  JS > var c=dba.getCluster()
#查看以后各节点列表 
 MySQL  172.16.16.10:3306 ssl  JS > c.status()

        "status": "OK",
        "statusText": "Cluster is ONLINE and can tolerate up to ONE failure.",
        "topology": {
            "172.16.16.10:3306": {
                "address": "172.16.16.10:3306",
                "memberRole": "PRIMARY",
                "mode": "R/W",
                "readReplicas": {},
                "replicationLag": null,
                "role": "HA",
                "status": "ONLINE",
                "version": "8.0.25"
            },
            "172.16.16.11:3306": {
                "address": "172.16.16.11:3306",
                "memberRole": "SECONDARY",
                "mode": "R/O",
                "readReplicas": {},
                "replicationLag": null,
                "role": "HA",
                "status": "ONLINE",
                "version": "8.0.25"
            },
            "172.16.16.12:3306": {
                "address": "172.16.16.12:3306",
                "memberRole": "SECONDARY",
                "mode": "R/O",
                "readReplicas": {},
                "replicationLag": null,
                "role": "HA",
                "status": "ONLINE",
                "version": "8.0.25"
            }
        },
        "topologyMode": "Single-Primary"
    },
    "groupInformationSourceMember": "172.16.16.10:3306"
}

#执行切换
 MySQL  172.16.16.10:3306 ssl  JS > c.setPrimaryInstance('172.16.16.11:3306')
Setting instance '172.16.16.11:3306' as the primary instance of cluster 'MGR1'...

#列举了三个节点各自产生的变动
Instance '172.16.16.10:3306' was switched from PRIMARY to SECONDARY.
Instance '172.16.16.11:3306' was switched from SECONDARY to PRIMARY.
Instance '172.16.16.12:3306' remains SECONDARY.

WARNING: The cluster internal session is not the primary member anymore. For cluster management operations please obtain a fresh cluster handle using dba.getCluster().

#实现切换
The instance '172.16.16.11:3306' was successfully elected as primary.

2. 切换单主 / 多主模式

在命令行模式下,能够调用 group_replication_switch_to_single_primary_mode()group_replication_switch_to_multi_primary_mode() 来切换单主 / 多主模式。

# 间接调用函数即可
mysql> select group_replication_switch_to_multi_primary_mode();
+--------------------------------------------------+
| group_replication_switch_to_multi_primary_mode() |
+--------------------------------------------------+
| Mode switched to multi-primary successfully.     |
+--------------------------------------------------+

#查看各节点状态
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST  | MEMBER_PORT | MEMBER_STATE | MEMBER_ROLE | MEMBER_VERSION |
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+
| group_replication_applier | af39db70-6850-11ec-94c9-00155d064000 | 172.16.16.10 |        3306 | ONLINE       | PRIMARY     | 8.0.25         |
| group_replication_applier | b05c0838-6850-11ec-a06b-00155d064000 | 172.16.16.11 |        3306 | ONLINE       | PRIMARY     | 8.0.25         |
| group_replication_applier | b0f86046-6850-11ec-92fe-00155d064000 | 172.16.16.12 |        3306 | ONLINE       | PRIMARY     | 8.0.25         |
+---------------------------+--------------------------------------+--------------+-------------+--------------+-------------+----------------+

#切换成单主模式时能够指定某个节点的 server_uuid,如果不指定则会依据规定主动抉择一个新的主节点
#在这里,我抉择了指定 mgr3 节点作为新主
mysql> select group_replication_switch_to_single_primary_mode('b0f86046-6850-11ec-92fe-00155d064000');
+-----------------------------------------------------------------------------------------+
| group_replication_switch_to_single_primary_mode('b0f86046-6850-11ec-92fe-00155d064000') |
+-----------------------------------------------------------------------------------------+
| Mode switched to single-primary successfully.                                           |
+-----------------------------------------------------------------------------------------+

在 MySQL Shell 中,能够调用 switchToSinglePrimaryMode() 以及 switchToMultiPrimaryMode() 函数进行切换。同样地,函数 switchToSinglePrimaryMode() 里也能够指定某个节点作为新的主节点。

 MySQL  172.16.16.10:3306 ssl  JS > var c=dba.getCluster()

#切换到多主模式 
 MySQL  172.16.16.10:3306 ssl  JS > c.switchToMultiPrimaryMode()
 
#切换到单主模式,这里我指定 mgr2 节点作为新主
 MySQL  172.16.16.10:3306 ssl  JS > c.switchToSinglePrimaryMode("172.16.16.11:3306")

留神 ,在曾经是单主模式时,无论是 group_replication_switch_to_single_primary_mode() 还是 switchToSinglePrimaryMode() 函数中指定另一个节点时是不会产生切换的,但也不会报错,只有提醒。

3. 增加新节点

接下来咱们演示如何向 MGR 集群中增加一个新节点。

首先,要先实现 MySQL Server 初始化,创立好 MGR 专用账户、设置好 MGR 服务通道等前置工作,这部分的操作能够参考前文 3. 装置部署 MGR 集群

接下来,间接执行命令 start group_replication 启动 MGR 服务即可,新增的节点会进入分布式复原这个步骤,它会从已有节点中主动抉择一个作为捐献者(donor),并自行决定是间接读取 binlog 进行复原,还是利用 Clone 进行全量复原。

如果是曾经在线运行一段时间的 MGR 集群,有肯定存量数据,这时候新节点退出可能会比较慢,倡议手动利用 Clone 进行一次全量复制。还记得后面创立 MGR 专用账户时,给加上了 BACKUP_ADMIN 受权吗,这时候就排上用场了,Clone 须要用到这个权限。

上面演示如何利用 Clone 进行一次全量数据恢复,假设要新增的节点是 172.16.16.13(给它命名为 mgr4)。

# 在 mgr4 上设置捐献者
#为了升高对 Primary 节点的影响,倡议抉择其余 Secondary 节点
mysql> set global clone_valid_donor_list='172.16.16.11:3306';

#停掉 mgr 服务(如果有的话),敞开 super_read_only 模式,而后开始复制数据
#留神这里要填写的端口是 3306(MySQL 失常服务端口),而不是 33061 这个 MGR 服务专用端口
mysql> stop group_replication; set global super_read_only=0; clone INSTANCE FROM GreatSQL@172.16.16.11:3306 IDENTIFIED BY 'GreatSQL';

全量复制完数据后,该节点会进行一次主动重启。重启结束后,再次确认 group_replication_group_namegroup_replication_local_addressgroup_replication_group_seeds 这些选项值是否正确,如果没问题,执行 start group_replication 后,该节点应该就能够失常退出集群了。

如果是用 MySQL Shell 增加新节点则更简略。先执行 MySQL Server 初始化,并执行 dba.dba.configureInstance() 创立 MGR 专用账号后。而后,连贯到 Primary 节点,间接调用 addInstance() 函数即可:

# 连贯到 Primary 节点
$ mysqlsh --uri GreatSQL@172.16.16.10:3306
 MySQL  172.16.16.10:3306 ssl  JS > var c=dba.getCluster()
 MySQL  172.16.16.10:3306 ssl  JS > c.addInstance('GreatSQL@172.16.16.13:3306')

WARNING: A GTID set check of the MySQL instance at '172.16.16.13:3306' determined that it contains transactions that do not originate from the cluster, which must be discarded before it can join the cluster. 
...
NOTE: 172.16.16.13:3306 is being cloned from 172.16.16.10:3306  #<-- 主动抉择一个 donor 节点
** Stage DROP DATA: Completed
** Clone Transfer
    FILE COPY  ############################################################  100%  Completed
    PAGE COPY  ############################################################  100%  Completed
    REDO COPY  ############################################################  100%  Completed

NOTE: 172.16.16.13:3306 is shutting down...

* Waiting for server restart... ready
* 172.16.16.13:3306 has restarted, waiting for clone to finish...
** Stage RESTART: Completed
* Clone process has finished: 72.43 MB transferred in about 1 second (~72.43 MB/s)

Incremental state recovery is now in progress.

* Waiting for distributed recovery to finish...
NOTE: '172.16.16.13:3306' is being recovered from '172.16.16.12:3306'
* Distributed recovery has finished

#新节点胜利退出结束
The instance '172.16.16.13:3306' was successfully added to the cluster.

#确认增加胜利,已在 MGR 集群列表中
 MySQL  172.16.16.10:3306 ssl  JS > c.describe()
{
    "clusterName": "MGR1",
    "defaultReplicaSet": {
        "name": "default",
        "topology": [
            {
                "address": "172.16.16.10:3306",
                "label": "172.16.16.10:3306",
                "role": "HA"
            },
            {
                "address": "172.16.16.11:3306",
                "label": "172.16.16.11:3306",
                "role": "HA"
            },
            {
                "address": "172.16.16.12:3306",
                "label": "172.16.16.12:3306",
                "role": "HA"
            },
            {
                "address": "172.16.16.13:3306",  <-- 新退出的节点
                "label": "172.16.16.13:3306",
                "role": "HA"
            }
        ],
        "topologyMode": "Single-Primary"
    }
} 

确认新节点增加胜利。

4. 删除节点

在命令行模式下,一个节点想退出 MGR 集群,间接执行 stop group_replication 即可,如果这个节点只是长期退出集群,前面还想加回集群,则执行 start group_replication 即可主动再退出。而如果是想彻底退出集群,则进行 MGR 服务后,执行 reset master; reset slave all; 重置所有复制(蕴含 MGR)相干的信息就能够了。

在 MySQL Shell 里,只需调用 removeInstance() 函数即可删除某个节点,例如:

 MySQL  172.16.16.10:3306 ssl  JS > c.removeInstance('172.16.16.13:3306');
The instance will be removed from the InnoDB cluster. Depending on the instance
being the Seed or not, the Metadata session might become invalid. If so, please
start a new session to the Metadata Storage R/W instance.

Instance '172.16.16.13:3306' is attempting to leave the cluster...

The instance '172.16.16.13:3306' was successfully removed from the cluster.

这就将该节点踢出集群了,并且会重置 group_replication_group_seedsgroup_replication_local_address 两个选项值。之后该节点如果想再退出集群,须要调用 addInstance() 从新加回。

5. 异样退出的节点从新加回

当节点因为网络断开、实例 crash 等异常情况与 MGR 集群断开连接后,这个节点的状态会变成 UNREACHABLE,待到超过 group_replication_member_expel_timeout + 5 秒后,集群会踢掉该节点。等到这个节点再次启动并执行 start group_replication,失常状况下,该节点应能主动从新加回集群。

在 MySQL Shell 里,能够调用 rejoinInstance() 函数将异样的节点从新加回集群:

 MySQL  172.16.16.10:3306 ssl  JS > c.rejoinInstance('172.16.16.13:3306');
 
Rejoining instance '172.16.16.13:3306' to cluster 'MGR1'...
The instance '172.16.16.13:3306' was successfully rejoined to the cluster.

6. 重启 MGR 集群

失常状况下,MGR 集群中的 Primary 节点退出时,剩下的节点会主动选出新的 Primary 节点。当最初一个节点也退出时,相当于整个 MGR 集群都敞开了。这时候任何一个节点启动 MGR 服务后,都不会主动成为 Primary 节点,须要在启动 MGR 服务前,先设置 group_replication_bootstrap_group=ON,使其成为疏导节点,再启动 MGR 服务,它才会成为 Primary 节点,后续启动的其余节点也能力失常退出集群。可自行测试,这里不再做演示。

P.S,第一个节点启动结束后,记得重置选项 group_replication_bootstrap_group=OFF,防止在后续的操作中导致 MGR 集群决裂。

如果是用 MySQL Shell 重启 MGR 集群,调用 rebootClusterFromCompleteOutage() 函数即可,它会主动判断各节点的状态,抉择其中一个作为 Primary 节点,而后拉起各节点上的 MGR 服务,实现 MGR 集群重启。能够参考这篇文章:万答 #12,MGR 整个集群挂掉后,如何能力主动选主,不必手动干涉

7. 小结

本文介绍了 MGR 集群几种常见治理保护操作方法,包含切换主节点,切换单主 / 多主模式,增加节点,删除节点,异样节点重退出,重启整个 MGR 集群等。总的来看,利用 MySQL Shell 治理 MGR 集群会更简略不便些,也有利于治理平台的封装,不过手工操作的形式也不能遗记,有些时候可能没有配套的 MySQL Shell 工具,就得靠手工了。

参考资料、文档

  • MySQL 8.0 Reference Manual
  • 数据库内核开发 – 温正湖
  • Group Replication 原理 – 宋利兵

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