从MGR集群到单机的GTID复制
为了方便描述，我们使用字母代码来标记实例：
群组有3个实例：A、B、C
单节点实例为D
当前主节点为A，
本案例为了验证利用GTID复制的强大性，在原来主节点A出故障后，通过GTID复制从新主节点B上同步，验证从机D末出现数据丢失。
1、把D上的slave进程停掉，并做复制信息清理。
2、A上增加一条数据后，退出群组复制，然后重新加入。
3、B成为新主节点，在B上也增加一条数据。
我们可以更进一步，把主库切换回A，然后在A上新增加数据，保持D从B复制，看看会不会有数据不复制过来。
测试案例说明：
1、MGR集群到单机的复制是可行的
2、GTID复制可以轻易解决从库在主机down掉指向新主机的问题，从新主库同步的配置变得如此轻松
3、当从库复制的主机在维护或者其他故障导致的变为MGR从库时，到单机的复制也不会中断，当然需要log_slave_updates=ON的支持。
群组有3个实例：A、B、C
单节点实例为D
当前主节点为A，
在群组集群主节点上配置普通复制slave专用用户：
CREATE USER repl@'%' IDENTIFIED BY 'repl';
GRANT REPLICATION SLAVE ON *.* TO repl@'%';在单节点上配置到主节点的复制，5.7上建议设置channel名称：
CHANGE MASTER TO
MASTER_HOST='127.0.0.1',
MASTER_USER='repl',
MASTER_PASSWORD='repl',
MASTER_PORT=24801,
MASTER_AUTO_POSITION = 1
for CHANNEL 'normal_replication';本案例为了验证利用GTID复制的强大性，在原来主节点A出故障后，通过GTID复制从新主节点B上同步，验证从机D末出现数据丢失。
1、把D上的slave进程停掉，并做复制信息清理。
2、A上增加一条数据后，退出群组复制，然后重新加入。
3、B成为新主节点，在B上也增加一条数据。
4、配置D从B复制，确认有最新的两条数据。
测试步骤：
D上操作：
mysql> reset slave all for channel 'normal_replication';
Query OK, 0 rows affected (0.00 sec)
mysql> show slave status\G
Empty set (0.00 sec)
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
+----+--------+
2 rows in set (0.00 sec)A上操作：
mysql> show global status like 'group_replication%';
+----------------------------------+--------------------------------------+
| Variable_name | Value |
+----------------------------------+--------------------------------------+
| group_replication_primary_member | 595937c0-4d9c-11e8-a819-00163e06ea60 |
+----------------------------------+--------------------------------------+
1 row in set (0.00 sec)
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 29d2ae7b-4de8-11e8-a27e-00163e06ea60 | myserver01 | 24802 | ONLINE |
| group_replication_applier | 2fdfc55d-4de8-11e8-a3af-00163e06ea60 | myserver01 | 24803 | ONLINE |
| group_replication_applier | 595937c0-4d9c-11e8-a819-00163e06ea60 | myserver01 | 24801 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
3 rows in set (0.00 sec)
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
+----+--------+
2 rows in set (0.00 sec)
mysql> insert into test.t1 values(3,'From A');
Query OK, 1 row affected (0.01 sec)
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
| 3 | From A |
+----+--------+
3 rows in set (0.00 sec)
mysql> stop group_replication;
Query OK, 0 rows affected (9.35 sec)
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 595937c0-4d9c-11e8-a819-00163e06ea60 | myserver01 | 24801 | OFFLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
1 row in set (0.00 sec)
mysql> start group_replication;
Query OK, 0 rows affected (4.29 sec)
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 29d2ae7b-4de8-11e8-a27e-00163e06ea60 | myserver01 | 24802 | ONLINE |
| group_replication_applier | 2fdfc55d-4de8-11e8-a3af-00163e06ea60 | myserver01 | 24803 | ONLINE |
| group_replication_applier | 595937c0-4d9c-11e8-a819-00163e06ea60 | myserver01 | 24801 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
3 rows in set (0.00 sec)
mysql> show global status like 'group_replication%';
+----------------------------------+--------------------------------------+
| Variable_name | Value |
+----------------------------------+--------------------------------------+
| group_replication_primary_member | 29d2ae7b-4de8-11e8-a27e-00163e06ea60 |
+----------------------------------+--------------------------------------+
1 row in set (0.00 sec)在B上操作：
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
| 3 | From A |
+----+--------+
3 rows in set (0.00 sec)
mysql> insert into test.t1 values(4,'From B');
2018-05-03T15:29:12.592666Z 23 [Note] Plugin group_replication reported: 'Primary had applied all relay logs, disabled conflict detection'
Query OK, 1 row affected (0.01 sec)
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
| 3 | From A |
| 4 | From B |
+----+--------+
4 rows in set (0.00 sec)在D上操作：
CHANGE MASTER TO
MASTER_HOST='127.0.0.1',
MASTER_USER='repl',
MASTER_PASSWORD='repl',
MASTER_PORT=24802,
MASTER_AUTO_POSITION = 1
for CHANNEL 'normal_replication';
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
+----+--------+
2 rows in set (0.00 sec)
mysql> CHANGE MASTER TO
-> MASTER_HOST='127.0.0.1',
-> MASTER_USER='repl',
-> MASTER_PASSWORD='repl',
-> MASTER_PORT=24802,
-> MASTER_AUTO_POSITION = 1
-> for CHANNEL 'normal_replication';
Query OK, 0 rows affected, 2 warnings (0.04 sec)
mysql> start slave;
Query OK, 0 rows affected (0.02 sec)
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 127.0.0.1
Master_User: repl
Master_Port: 24802
Connect_Retry: 60
Master_Log_File: binlog.000004
Read_Master_Log_Pos: 2203
Relay_Log_File: myserver01-relay-bin-normal_replication.000002
Relay_Log_Pos: 1191
Relay_Master_Log_File: binlog.000004
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 2203
Relay_Log_Space: 1414
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 2
Master_UUID: 29d2ae7b-4de8-11e8-a27e-00163e06ea60
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set: aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:22-24
Executed_Gtid_Set: aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:1-24
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name: normal_replication
Master_TLS_Version:
1 row in set (0.00 sec)
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
| 3 | From A |
| 4 | From B |
+----+--------+
4 rows in set (0.00 sec)我们可以更进一步，把主库切换回A，然后在A上新增加数据，保持D从B复制，看看会不会有数据不复制过来。
在B上操作：
mysql> stop group_replication;
Query OK, 0 rows affected (9.54 sec)
mysql> start group_replication;
Query OK, 0 rows affected (3.08 sec)在A上操作：
mysql> show global status like 'group_replication%';
+----------------------------------+--------------------------------------+
| Variable_name | Value |
+----------------------------------+--------------------------------------+
| group_replication_primary_member | 595937c0-4d9c-11e8-a819-00163e06ea60 |
+----------------------------------+--------------------------------------+
1 row in set (0.01 sec)
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 29d2ae7b-4de8-11e8-a27e-00163e06ea60 | myserver01 | 24802 | ONLINE |
| group_replication_applier | 2fdfc55d-4de8-11e8-a3af-00163e06ea60 | myserver01 | 24803 | ONLINE |
| group_replication_applier | 595937c0-4d9c-11e8-a819-00163e06ea60 | myserver01 | 24801 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
3 rows in set (0.00 sec)
mysql> insert into test.t1 values(5,'From A');
Query OK, 1 row affected (0.00 sec)
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
| 3 | From A |
| 4 | From B |
| 5 | From A |
+----+--------+
5 rows in set (0.00 sec)在D上操作：
mysql> select * from test.t1;
+----+--------+
| c1 | c2 |
+----+--------+
| 1 | Luis |
| 2 | from A |
| 3 | From A |
| 4 | From B |
| 5 | From A |
+----+--------+
5 rows in set (0.00 sec)
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 127.0.0.1
Master_User: repl
Master_Port: 24802
Connect_Retry: 60
Master_Log_File: binlog.000004
Read_Master_Log_Pos: 2766
Relay_Log_File: myserver01-relay-bin-normal_replication.000002
Relay_Log_Pos: 1754
Relay_Master_Log_File: binlog.000004
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 2766
Relay_Log_Space: 1977
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 2
Master_UUID: 29d2ae7b-4de8-11e8-a27e-00163e06ea60
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set: aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:22-26
Executed_Gtid_Set: aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:1-26
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name: normal_replication
Master_TLS_Version:
1 row in set (0.00 sec)测试案例说明：
1、MGR集群到单机的复制是可行的
2、GTID复制可以轻易解决从库在主机down掉指向新主机的问题，从新主库同步的配置变得如此轻松
3、当从库复制的主机在维护或者其他故障导致的变为MGR从库时，到单机的复制也不会中断，当然需要log_slave_updates=ON的支持。