2-21 MGR 集群搭建

介绍

MGR 是MySQL 是数据库未来发展的一个重要方向

引擎

2.3 设置hostname和ip映射

1 ）

设置 /etc/hosts

三台同样的配置

2) 登录数据库开始授权

grant replication slave on *.* to repl@'192.168.24.%' identified by '123456';

3 ）打开/ etc/my.cnf 的配置文件

Group Replication

server_id = 100 #服务ID

gtid_mode = ON #全局事务

enforce_gtid_consistency = ON #强制GTID的一致性

master_info_repository = TABLE #将master.info元数据保存在系统表中

relay_log_info_repository = TABLE #将relay.info元数据保存在系统表中

binlog_checksum = NONE #禁用二进制日志事件校验

log_slave_updates = ON #级联复制

log_bin = binlog #开启二进制日志记录

binlog_format= ROW #以行的格式记录

transaction_write_set_extraction = XXHASH64 #使用哈希算法将其编码为散列

loose-group_replication_group_name = 'ce9be252-2b71-11e6-b8f4-00212844f856' #加入的组名

loose-group_replication_start_on_boot = off #不自动启用组复制集群

loose-group_replication_local_address = 'xuegod1:33061' #以本机端口33061接受来自组中成员的传入连接

loose-group_replication_group_seeds = 'xuegod1:33061, xuegod2:33062, xuegod1:33063' #组中成员访问表

loose-group_replication_bootstrap_group = off #不启用引导组

注释掉第一行否则会报错

4 ）重启mysql 服务器

5 ）登入mysql

修改master

change master to master_user='repl',master_password='123456' for channel 'group_replication_recovery';

6 ) 安装插件

install PLUGIN group_replication SONAME 'group_replication.so';

7 ）再次使用show 查看一下就会看到

show flugins

8 ) 启动第一个节点手工开机引导组进入mysql 集群以后

set global group_replication_bootstrap_group=ON;

9 ) 开启引导

4. 下面分别记录下 MGR 基于单主模式和多主模式的集群环境部署过程

4.1 准备环境

三台服务器

172.16.60.211 MGR-node1 server_id=1

172.16.60.212 MGR-node2 server_id=2

172.16.60.213 MGR-node3 server_id=3

[root@MGR-node1 ~]# cat /etc/redhat-release

CentOS Linux release 7.5.1804 (Core)

为了方便实验，关闭所有节点的防火墙

[root@MGR-node1 ~]# systemctl stop firewalld

[root@MGR-node1 ~]# firewall-cmd --state

not running

[root@MGR-node1 ~]# cat /etc/sysconfig/selinux |grep "SELINUX=disabled"

SELINUX=disabled

[root@MGR-node1 ~]# setenforce 0

setenforce: SELinux is disabled

[root@MGR-node1 ~]# getenforce

Disabled

特别要注意一个关键点: 必须保证各个mysql节点的主机名不一致，并且能通过主机名找到各成员！

则必须要在每个节点的/etc/hosts里面做主机名绑定，否则后续将节点加入group组会失败！报错RECOVERING！！

[root@MGR-node1 ~]# cat /etc/hosts

........

172.16.60.211 MGR-node1

172.16.60.212 MGR-node2

172.16.60.213 MGR-node3

4.2 在三个节点上安装Mysql5.7

在三个mysql节点机上使用yum方式安装Mysql5.7，参考：https://www.cnblogs.com/kevingrace/p/8340690.html

安装MySQL yum资源库

[root@MGR-node1 ~]# yum localinstall https://dev.mysql.com/get/mysql57-community-release-el7-8.noarch.rpm

安装MySQL 5.7

[root@MGR-node1 ~]# yum install -y mysql-community-server

启动MySQL服务器和MySQL的自动启动

[root@MGR-node1 ~]# systemctl start mysqld.service

[root@MGR-node1 ~]# systemctl enable mysqld.service

设置登录密码

由于MySQL从5.7开始不允许首次安装后使用空密码进行登录！为了加强安全性，系统会随机生成一个密码以供管理员首次登录使用，

这个密码记录在/var/log/mysqld.log文件中，使用下面的命令可以查看此密码：

[root@MGR-node1 ~]# cat /var/log/mysqld.log|grep 'A temporary password'

2019-01-11T05:53:17.824073Z 1 [Note] A temporary password is generated for root@localhost: TaN.k:*Qw2xs

使用上面查看的密码TaN.k:*Qw2xs 登录mysql，并重置密码为123456

[root@MGR-node1 ~]# mysql -p #输入默认的密码：TaN.k:*Qw2xs

.............

mysql> set global validate_password_policy=0;

Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length=1;

Query OK, 0 rows affected (0.00 sec)

mysql> set password=password("123456");

Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> flush privileges;

Query OK, 0 rows affected (0.00 sec)

查看mysql版本

[root@MGR-node1 ~]# mysql -p123456

........

mysql> select version();

+-----------+

| version() |

+-----------+

| 5.7.24 |

+-----------+

1 row in set (0.00 sec)

=====================================================================

温馨提示

mysql5.7通过上面默认安装后，执行语句可能会报错：

ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

这个报错与Mysql 密码安全策略validate_password_policy的值有关，validate_password_policy可以取0、1、2三个值：

解决办法：

set global validate_password_policy=0;

set global validate_password_length=1;

4.3 安装和配置MGR信息

1) 配置所有节点的组复制信息

MGR-node01节点

[root@MGR-node1 ~]# cp /etc/my.cnf /etc/my.cnf.bak

[root@MGR-node1 ~]# >/etc/my.cnf

[root@MGR-node1 ~]# vim /etc/my.cnf

[mysqld]

datadir = /var/lib/mysql

socket = /var/lib/mysql/mysql.sock

symbolic-links = 0

log-error = /var/log/mysqld.log

pid-file = /var/run/mysqld/mysqld.pid

#复制框架

server_id=1

gtid_mode=ON

enforce_gtid_consistency=ON

binlog_checksum=NONE

log_bin=binlog

log_slave_updates=ON

binlog_format=ROW

master_info_repository=TABLE

relay_log_info_repository=TABLE

#组复制设置

#server必须为每个事务收集写集合，并使用XXHASH64哈希算法将其编码为散列

transaction_write_set_extraction=XXHASH64

#告知插件加入或创建组命名，UUID

loose-group_replication_group_name="aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"

#server启动时不自启组复制,为了避免每次启动自动引导具有相同名称的第二个组,所以设置为OFF。

loose-group_replication_start_on_boot=off

#告诉插件使用IP地址，端口24901用于接收组中其他成员转入连接

loose-group_replication_local_address="172.16.60.211:24901"

#启动组server，种子server，加入组应该连接这些的ip和端口；其他server要加入组得由组成员同意

loose-group_replication_group_seeds="172.16.60.211:24901,172.16.60.212:24901,172.16.60.213:24901"

loose-group_replication_bootstrap_group=off

report_host=172.16.60.211

report_port=3306

如上配置完成后, 将MGR-node1节点的/etc/my.cnf文件拷贝到其他两个节点

[root@MGR-node1 ~]# rsync -e "ssh -p22" -avpgolr /etc/my.cnf root@172.16.60.212:/etc/

[root@MGR-node1 ~]# rsync -e "ssh -p22" -avpgolr /etc/my.cnf root@172.16.60.213:/etc/

3个MGR节点除了server_id、loose-group_replication_local_address、report_host 三个参数不一样外，其他保持一致。

所以待拷贝完成后, 分别修改MGR-node2和MGR-node3节点/etc/my.cnf文件的server_id、loose-group_replication_local_address、report_host 三个参数

2) 配置完成后, 要一次启动数据库，安装MGR插件，设置复制账号（所有MGR节点都要执行）

[root@MGR-node1 ~]# systemctl restart mysqld

[root@MGR-node1 ~]# mysql -p123456

.............

mysql> INSTALL PLUGIN group_replication SONAME 'group_replication.so';

Query OK, 0 rows affected (0.13 sec)

mysql> SET SQL_LOG_BIN=0;

Query OK, 0 rows affected (0.00 sec)

mysql> CREATE USER repl@'%' IDENTIFIED BY 'repl';

Query OK, 0 rows affected (0.00 sec)

mysql> GRANT REPLICATION SLAVE ON *.* TO repl@'%';

Query OK, 0 rows affected (0.00 sec)

mysql> FLUSH PRIVILEGES;

Query OK, 0 rows affected (0.00 sec)

mysql> SET SQL_LOG_BIN=1;

Query OK, 0 rows affected (0.00 sec)

mysql> CHANGE MASTER TO MASTER_USER='repl', MASTER_PASSWORD='repl' FOR CHANNEL 'group_replication_recovery';

Query OK, 0 rows affected, 2 warnings (0.21 sec)

4.4 启动MGR单主模式

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1) 启动MGR，在主库(172.16.60.11)节点上上执行

[root@MGR-node1 ~]# mysql -p123456

...............

mysql> SET GLOBAL group_replication_bootstrap_group=ON;

Query OK, 0 rows affected (0.00 sec)

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected (2.31 sec)

mysql> SET GLOBAL group_replication_bootstrap_group=OFF;

Query OK, 0 rows affected (0.00 sec)

查看MGR组信息

mysql> SELECT * FROM performance_schema.replication_group_members;

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

1 row in set (0.01 sec)

2) 在其他节点加入MGR集群，在从库（172.16.60.212，172.16.60.213）上执行

[root@MGR-node2 ~]# mysql -p123456

................

mysql> START GROUP_REPLICATION;

ERROR 3092 (HY000): The server is not configured properly to be an active member of the group. Please see more details on error log.

查看日志:

[root@MGR-node2 ~]# tail -2000 /var/log/mysqld.log

.....................

2019-03-04T09:11:30.683714Z 0 [ERROR] Plugin group_replication reported: 'This member has more executed transactions than those present in the group. Local transactions: 87135ebb-3e51-11e9-8931-005056880888:1-2 > Group transactions: 851d03bb-3e51-11e9-8f8d-00505688047c:1-2,

8769f936-3e51-11e9-acaa-005056ac6820:1-2,

aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:1-4'

2019-03-04T09:11:30.683817Z 0 [Warning] Plugin group_replication reported: 'The member contains transactions not present in the group. It is only allowed to join due to group_replication_allow_local_disjoint_gtids_join option'

解决办法:

mysql> set global group_replication_allow_local_disjoint_gtids_join=ON;

Query OK, 0 rows affected, 1 warning (0.00 sec)

然后再接着加入MGR集群

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected, 1 warning (5.14 sec)

3) 再次查看MGR组信息 (在三个MGR节点上都可以查看)

mysql> SELECT * FROM performance_schema.replication_group_members;

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

3 rows in set (0.00 sec)

发现新加入的MGR-node2 , MGR-node3两个节点在集群里的状态是RECOVERING!!!

查看日志

[root@MGR-node3 ~]# tail -2000 /var/log/mysqld.log

.....................

2019-03-04T09:15:35.146740Z 734 [ERROR] Slave I/O for channel 'group_replication_recovery': Got fatal error 1236 from master when

reading data from binary log: 'The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has

purged binary logs containing GTIDs that the slave requires.', Error_code: 1236

解决办法:

登录主库172.16.60.211, 查看被purge的GTID：

[root@MGR-node1 ~]# mysql -p123456

....................

mysql> show global variables like 'gtid_purged';

+---------------+------------------------------------------+

| Variable_name | Value |

+---------------+------------------------------------------+

| gtid_purged | 8769f936-3e51-11e9-acaa-005056ac6820:1-2 |

+---------------+------------------------------------------+

1 row in set (0.00 sec)

接着在两个从库172.16.60.212, 172.16.60.213的数据库上执行下面命令，即跳过这个GTID：

mysql> STOP GROUP_REPLICATION;

Query OK, 0 rows affected (10.14 sec)

mysql> reset master;

Query OK, 0 rows affected (0.06 sec)

mysql> set global gtid_purged = '8769f936-3e51-11e9-acaa-005056ac6820:1-2';

Query OK, 0 rows affected (0.24 sec)

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected, 1 warning (3.49 sec)

再次查看查看MGR组信息 (在三个MGR节点上都可以查看),

mysql> SELECT * FROM performance_schema.replication_group_members;

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

3 rows in set (0.00 sec)

通过上面可以看出: 三个MGR节点状态为online，并且主节点为172.16.60.211，只有主节点可以写入，其他两个MGR节点只读，MGR单主模式搭建成功。

==============================================================================

验证下MGR单主模式下节点数据的同步以及读写操作:

先在主库节点172.16.60.211上创建测试数据库

[root@MGR-node1 ~]# mysql -p123456

..............

mysql> CREATE DATABASE kevin CHARACTER SET utf8 COLLATE utf8_general_ci;

Query OK, 1 row affected (0.06 sec)

mysql> use kevin;

Database changed

mysql> create table if not exists haha (id int(10) PRIMARY KEY AUTO_INCREMENT,name varchar(50) NOT NULL);

Query OK, 0 rows affected (0.24 sec)

mysql> insert into kevin.haha values(1,"wangshibo"),(2,"guohuihui"),(3,"yangyang"),(4,"shikui");

Query OK, 4 rows affected (0.13 sec)

Records: 4 Duplicates: 0 Warnings: 0

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

+----+-----------+

4 rows in set (0.00 sec)

接着在其他的两个从节点172.16.60.212和172.16.60.213上查看数据, 发现主库数据已经同步到两个从库上了

[root@MGR-node2 ~]# mysql -p123456

..................

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

+----+-----------+

4 rows in set (0.00 sec)

然后尝试在两个从库上更新数据, 发现更新失败! 因为这是MGR单主模式, 从库只能进行读操作, 不能进行写操作!

[root@MGR-node3 ~]# mysql -p123456

.................

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

+----+-----------+

4 rows in set (0.00 sec)

mysql> delete from kevin.haha where id>3;

ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement

mysql> insert into kevin.haha values(11,"beijing"),(12,"shanghai"),(13,"anhui");

ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement

只有在主库上才能进行写操作

[root@MGR-node1 ~]# mysql -p123456

..............

mysql> insert into kevin.haha values(11,"beijing"),(12,"shanghai"),(13,"anhui");

Query OK, 3 rows affected (0.15 sec)

Records: 3 Duplicates: 0 Warnings: 0

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

| 11 | beijing |

| 12 | shanghai |

| 13 | anhui |

+----+-----------+

7 rows in set (0.00 sec)

4.5 切换到多主模式

MGR切换模式需要重新启动组复制，因些需要在所有节点上先关闭组复制，设置 group_replication_single_primary_mode=OFF 等参数，再启动组复制。

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1) 停止组复制(在所有MGR节点上执行)：

mysql> stop group_replication;

Query OK, 0 rows affected (9.08 sec)

mysql> set global group_replication_single_primary_mode=OFF;

Query OK, 0 rows affected (0.00 sec)

mysql> set global group_replication_enforce_update_everywhere_checks=ON;

Query OK, 0 rows affected (0.00 sec)

2) 随便选择某个MGR节点执行 (比如这里选择在MGR-node1节点):

[root@MGR-node1 ~]# mysql -p123456

...............

mysql> SET GLOBAL group_replication_bootstrap_group=ON;

Query OK, 0 rows affected (0.00 sec)

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected (2.20 sec)

mysql> SET GLOBAL group_replication_bootstrap_group=OFF;

Query OK, 0 rows affected (0.00 sec)

3) 然后在其他的MGR节点执行 (这里指MGR-node2和MGR-node3节点上执行):

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected, 1 warning (5.89 sec)

4) 查看MGR组信息 (在任意一个MGR节点上都可以查看)

mysql> SELECT * FROM performance_schema.replication_group_members;

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

3 rows in set (0.00 sec)

可以看到所有MGR节点状态都是online，角色都是PRIMARY，MGR多主模式搭建成功。

=========================================

验证下MGR多主模式的节点数据同步:

在MGR-node1节点更新数据:

[root@MGR-node1 ~]# mysql -p123456

.................

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

| 11 | beijing |

| 12 | shanghai |

| 13 | anhui |

+----+-----------+

7 rows in set (0.00 sec)

mysql> delete from kevin.haha where id>10;

Query OK, 3 rows affected (0.08 sec)

在MGR-node2节点更新数据

[root@MGR-node2 ~]# mysql -p123456

...............

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

+----+-----------+

4 rows in set (0.00 sec)

mysql> insert into kevin.haha values(11,"beijing"),(12,"shanghai"),(13,"anhui");

Query OK, 3 rows affected (0.08 sec)

Records: 3 Duplicates: 0 Warnings: 0

在MGR-node3节点更新数据

[root@MGR-node3 ~]# mysql -p123456

.............

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

| 11 | beijing |

| 12 | shanghai |

| 13 | anhui |

+----+-----------+

7 rows in set (0.00 sec)

mysql> delete from kevin.haha where id>11;

Query OK, 2 rows affected (0.14 sec)

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

| 11 | beijing |

+----+-----------+

5 rows in set (0.00 sec)

如上, MGR多主模式下, 所有节点都可以进行读写操作.

4.6 切回单主模式

1) 停止组复制(在所有MGR节点上执行)：

mysql> stop group_replication;

Query OK, 0 rows affected (9.29 sec)

mysql> set global group_replication_enforce_update_everywhere_checks=OFF;

Query OK, 0 rows affected (0.00 sec)

mysql> set global group_replication_single_primary_mode=ON;

Query OK, 0 rows affected (0.00 sec)

2) 选择一个节点作为主节点, 在主节点上执行 (这里选择MGR-node1节点作为主节点)

[root@MGR-node1 ~]# mysql -p123456

................

mysql> SET GLOBAL group_replication_bootstrap_group=ON;

Query OK, 0 rows affected (0.00 sec)

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected (2.12 sec)

mysql> SET GLOBAL group_replication_bootstrap_group=OFF;

Query OK, 0 rows affected (0.00 sec)

3) 在其他剩余的节点, 也就是从库节点上执行 (这里从库节点指的就是MGR-node2和MGR-node3):

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected, 1 warning (6.16 sec)

4) 查看MGR组信息 (在任意一个MGR节点上都可以查看)

mysql> SELECT * FROM performance_schema.replication_group_members;

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

3 rows in set (0.00 sec)

这样就又切回到MGR单主模式了, 其中172.16.60.211是主节点,具有写权限. 另外两个节点172.16.60.212和172.16.60.213是从库节点, 只能读不能写.

4.7 故障切换

1) 单主模式

如果主节点挂掉了, 通过选举程序会从从库节点中选择一个作为主库节点. 如下模拟故障:

关闭主库MGR-node1的mysqld服务

[root@MGR-node1 ~]# systemctl stop mysqld

接着在其他节点上查看MGR组信息. 比如在MGR-node2节点查看

[root@MGR-node2 ~]# mysql -p123456

mysql> SELECT * FROM performance_schema.replication_group_members;

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

2 rows in set (0.00 sec)

尝试在MGR-node2节点更新数据

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

| 11 | beijing |

| 12 | shanghai |

| 13 | anhui |

+----+-----------+

7 rows in set (0.00 sec)

mysql> delete from kevin.haha where id>10;

Query OK, 3 rows affected (0.06 sec)

如上, 发现在之前的主库MGR-node1节点挂掉后, MGR-node2节点可以进行写操作了, 说明此时已经选举MGR-node2节点为新的主节点了

那么,MGR-node3节点还是从节点, 只能读不能写

[root@MGR-node3 ~]# mysql -p123456

..............

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

+----+-----------+

4 rows in set (0.00 sec)

mysql> insert into kevin.haha values(11,"beijing"),(12,"shanghai"),(13,"anhui");

ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement

然后再恢复MGR-node1节点, 恢复后, 需要手动激活下该节点的组复制功能

[root@MGR-node1 ~]# systemctl start mysqld

[root@MGR-node1 ~]# mysql -p123456

...............

mysql> START GROUP_REPLICATION;

Query OK, 0 rows affected (3.15 sec)

mysql> SELECT * FROM performance_schema.replication_group_members;

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

+---------------------------+--------------------------------------+---------------+-------------+--------------+

3 rows in set (0.00 sec)

mysql> select * from kevin.haha;

+----+-----------+

| id | name |

+----+-----------+

| 1 | wangshibo |

| 2 | guohuihui |

| 3 | yangyang |

| 4 | shikui |

+----+-----------+

4 rows in set (0.00 sec)

mysql> insert into kevin.haha values(11,"beijing"),(12,"shanghai"),(13,"anhui");

ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement

发现MGR-node1节点恢复后, 则变为了从库节点, 只能读不能写.

如果从节点挂了, 恢复后, 只需要手动激活下该节点的组复制功能("START GROUP_REPLICATION;"),

即可正常加入到MGR组复制集群内并自动同步其他节点数据.

=============================================================

2) 多主模式

如果某个节点挂了, 则其他的节点继续进行同步.

当故障节点恢复后, 只需要手动激活下该节点的组复制功能("START GROUP_REPLICATION;"),

即可正常加入到MGR组复制集群内并自动同步其他节点数据.