在之前的博客已经介绍了MGR单主模式的部署准备以及如何部署，这节内容为如何部署多主模式
MGR默认部署完后是单主模式，我们需要做些更改来切换到多主模式，切换需要重启引导组复制
我们假设已经搭建好了单主模式
检查当前模式
任意服务器
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 18f5da07-a096-11ea-8c70-000c290e1abf | db01 | 3306 | ONLINE |
| group_replication_applier | 7d3e894a-a0a9-11ea-82f8-000c29a7fff7 | db03 | 3306 | ONLINE |
| group_replication_applier | dfe895a8-a0df-11ea-bb7d-000c296190c1 | db02 | 3306 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
所有节点停止组复制
在所有的节点执行，将组复制停止
mysql> stop group_replication;Db01（单主模式里面的可读可写的引导组）
#将单组模式置为off状态，在数据库重启之后该参数失效，如果不想让其失效写到配置文件里面
mysql> show variables like '%group_replication_single_primary_mode%';
+---------------------------------------+-------+
| Variable_name | Value |
+---------------------------------------+-------+
| group_replication_single_primary_mode | ON |
+---------------------------------------+-------+
set global group_replication_single_primary_mode=off;
#检查冲突，因为多主模式可能会产生冲突，比如在多个节点修改同一条记录，单组模式下是off状态，因为在多个节点进行写入操作可能会造成冲突
mysql> show variables like '%group_replication_enforce_update_everywhere_checks%';
+----------------------------------------------------+-------+
| Variable_name | Value |
+----------------------------------------------------+-------+
| group_replication_enforce_update_everywhere_checks | OFF |
+----------------------------------------------------+-------+
set global group_replication_enforce_update_everywhere_checks=ON;
#引导多主模式组
#设置为启动组，启动组复制，然后将其关闭，单组模式下也会执行该步骤，所以主要是设置上面两个参数
SET GLOBAL group_replication_bootstrap_group=ON;
START GROUP_REPLICATION;
SET GLOBAL group_replication_bootstrap_group=OFF;
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 18f5da07-a096-11ea-8c70-000c290e1abf | db01 | 3306 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
Db02 比上面少了启动引导组
set global group_replication_single_primary_mode=off;
set global group_replication_enforce_update_everywhere_checks=ON;
start group_replication;
select * from performance_schema.replication_group_members;
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 18f5da07-a096-11ea-8c70-000c290e1abf | db01 | 3306 | ONLINE |
| group_replication_applier | dfe895a8-a0df-11ea-bb7d-000c296190c1 | db02 | 3306 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
Db03 照葫芦画瓢Db02
set global group_replication_single_primary_mode=off;
set global group_replication_enforce_update_everywhere_checks=ON;
start group_replication;
select * from performance_schema.replication_group_members;
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 18f5da07-a096-11ea-8c70-000c290e1abf | db01 | 3306 | ONLINE |
| group_replication_applier | 7d3e894a-a0a9-11ea-82f8-000c29a7fff7 | db03 | 3306 | ONLINE |
| group_replication_applier | dfe895a8-a0df-11ea-bb7d-000c296190c1 | db02 | 3306 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+测试
db01、db02、db03节点上:
| create database db; use db; create table tbs01(id int primary key,name varchar(20)); insert into tbs01 values(1, 't1'); --db01节点执行 insert into tbs01 values(2, 't2'); --db02节点执行 insert into tbs01 values(3, 't3'); --db03节点执行 |
当环境搭建完三个节点是可以进行插入的，多主模式下所有节点可以进行写入
mysql> show variables like '%read_only%'; 所有节点执行，可以看到相同结果
+-----------------------+-------+
| Variable_name | Value |
+-----------------------+-------+
| innodb_read_only | OFF |
| read_only | OFF |
| super_read_only | OFF |
| transaction_read_only | OFF |
| tx_read_only | OFF |
+-----------------------+-------+
可以看到在单组模式下通过修改两个参数就可以变为多组模式