MySQL分组复制提供的功能很强大，但是有时会出现一些问题，或者使用上存在一些限制主要包括：
(1)分组复制的限制。
(a)存储引擎只能是InnoDB。
(b)二进制日志格式只支持ROW格式。
(c)只支持使用GTID模式。
(d)每个分组最多只支持9个成员节点。
(2)数据表必须有主键。
mysql> create table test (name varchar(100));
Query OK, 0 rows affected (0.05 sec)
mysql> insert into test values( now()),(now());
ERROR 3098 (HY000): The table does not comply with the requirements by an external plugin.
查看日志：
2017-08-19T06:23:22.253181Z 13 [ERROR] Plugin group_replication reported: ‘Table test does not have any PRIMARY KEY. This is not compatible with Group Replication‘
2017-08-19T06:24:18.493848Z 13 [ERROR] Plugin group_replication reported: ‘Table test does not have any PRIMARY KEY. This is not compatible with Group Replication‘
解决办法：
创建有主键的数据表。
mysql> create table test ( name varchar(100) primary key);
Query OK, 0 rows affected (0.02 sec)
mysql> insert into test (name) values (‘001‘);
Query OK, 1 row affected (0.02 sec)
mysql> insert into test (name) values (‘002‘);
Query OK, 1 row affected (0.01 sec)
mysql> insert into test (name) values (‘003‘);
Query OK, 1 row affected (0.00 sec)
mysql> insert into test (name) values (now());
Query OK, 1 row affected (0.01 sec)
(3)数据库已经存在。
日志中出现了数据库已经存在而无法创建数据库的错误。
2017-08-19T06:51:50.784471Z 28 [ERROR] Slave SQL for channel ‘group_replication_recovery‘: Error ‘Can‘t create database ‘test‘; database exists‘ on query. Default database: ‘test‘. Query: ‘create database test‘, Error_code: 1007
2017-08-19T06:51:50.784523Z 28 [Warning] Slave: Can‘t create database ‘test‘; database exists Error_code: 1007
2017-08-19T06:51:50.784530Z 28 [ERROR] Error running query, slave SQL thread aborted. Fix the problem, and restart the slave SQL thread with "SLAVE START". We stopped at log ‘binlog.000001‘ position 1082
解决办法：
mysql> stop group_replication;
Query OK, 0 rows affected (9.43 sec)
mysql> drop database test;
ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement
mysql> set global super_read_only=0;
Query OK, 0 rows affected (0.00 sec)
mysql> drop database test;
Query OK, 0 rows affected (0.00 sec)
mysql> set global super_read_only=1;
Query OK, 0 rows affected (0.00 sec)
mysql> set global group_replication_allow_local_disjoint_gtids_join=ON;
Query OK, 0 rows affected (0.00 sec)
mysql> start group_replication;
Query OK, 0 rows affected (3.19 sec)
为了防止在MySQL的节点在启动时出现此问题，可将下面的配置加入MySQL配置文件。
loose-group_replication_allow_local_disjoint_gtids_join=on