MGR多主（Multi-Primary）模式和单主（Single-Primary）模式切换

MGR多主（Multi-Primary）模式和单主（Single-Primary）模式切换

一、单主切换到多主

​ 1、对每一个 MySQL 节点配置如下参数，并写入 my.cnf 配置文件

stop group_replication;
#关闭单主模式的参数
set global group_replication_single_primary_mode=off;
#开启多主模式的参数														
set global group_replication_enforce_update_everywhere_checks=on;


loose-group_replication_single_primary_mode=off
loose-group_replication_enforce_update_everywhere_checks=on

​

​ 2、在其中一个节点，打开 group_replication_bootstrap_group 为 on，并开启组复制，成功后再关闭

set global group_replication_bootstrap_group=on;
start group_replication;
set global group_replication_bootstrap_group=off;

​ 3、另外两个节点逐一开启组复制，加入集群环境，并通过视图查看集群情况

mysql> start group_replication;
Query OK, 0 rows affected (5.78 sec)

mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 839d3796-a8a1-11ea-b1db-00505636b68c | ip136       |        3306 | ONLINE       |
| group_replication_applier | e741120b-a7e9-11ea-9af7-0050563bbd20 | ip135       |        3306 | ONLINE       |
| group_replication_applier | f44ecd83-a8d1-11ea-ad97-0050562512fc | ip137       |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
3 rows in set (0.00 sec)

mysql> show global variables like '%read_only%';
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| innodb_read_only      | OFF   |
| read_only             | OFF   |
| super_read_only       | OFF   |
| transaction_read_only | OFF   |
| tx_read_only          | OFF   |
+-----------------------+-------+
5 rows in set (0.00 sec)

二、多主切换到单主

1、停止组复制

stop group_replication;
set global group_replication_enforce_update_everywhere_checks=off;
set global group_replication_single_primary_mode=on;

2、选择一个节点,打开 group_replication_bootstrap_group 为 on，并开启组复制，成功后再关闭

set global group_replication_bootstrap_group=on;
start group_replication;
set global group_replication_bootstrap_group=off;

3、另外两个节点逐一开启组复制，加入集群环境，并通过视图查看集群情况

start group_replication;
select * from performance_schema.replication_group_members;

#查看 Primary 成员
select *from  performance_schema.replication_group_members where member_id =(select variable_value from performance_schema.global_status WHERE VARIABLE_NAME= 'group_replication_primary_member');