slave have equal MySQL server UUIDs

Recently when deploying the MySQL master-slave replication architecture, I encountered "Last_IO_Error: Fatal error: The slave I/O thread stops because master and slave have equal MySQL server UUIDs; these UUIDs must be different for replication to work." this error message. That is, the same UUID is used in the master-slave architecture. Check the server_id system variable, it is already a different setting, what is the reason? What follows is a detailed description.

1、错误消息
mysql> show slave staus;
 
Last_IO_Error: Fatal error: The slave I/O thread stops because master and slave have equal MySQL server UUIDs; 
these UUIDs must be different for replication to work.
 
2、查看主从的server_id变量
master_mysql> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id     | 33    |
+---------------+-------+

slave_mysql> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id     | 11    |
+---------------+-------+
-- 从上面的情形可知，主从mysql已经使用了不同的server_id

3、解决故障
###查看auto.cnf文件
[root@dbsrv1 ~] cat /data/mysqldata/auto.cnf  ### 主上的uuid
[auto]
server-uuid=62ee10aa-b1f7-11e4-90ae-080027615026

[root@dbsrv2 ~]# more /data/mysqldata/auto.cnf ###从上的uuid，果然出现了重复，原因是克隆了虚拟机，只改server_id不行
[auto]
server-uuid=62ee10aa-b1f7-11e4-90ae-080027615026

[root@dbsrv2 ~]# mv /data/mysqldata/auto.cnf  /data/mysqldata/auto.cnf.bk  ###重命名该文件
[root@dbsrv2 ~]# service mysql restart          ###重启mysql
Shutting down MySQL.[  OK  ]
Starting MySQL.[  OK  ]
[root@dbsrv2 ~]# more /data/mysqldata/auto.cnf  ###重启后自动生成新的auto.cnf文件，即新的UUID
[auto]
server-uuid=6ac0fdae-b5d7-11e4-a9f3-0800278ce5c9


###再次查看slave的状态已经正常
[root@dbsrv1 ~]# mysql -uroot -pxxx -e "show slave status\G"|grep Running
Warning: Using a password on the command line interface can be insecure.
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
      Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it

###主库端查看自身的uuid
master_mysql> show variables like 'server_uuid';
+---------------+--------------------------------------+
| Variable_name | Value                                |
+---------------+--------------------------------------+
| server_uuid   | 62ee10aa-b1f7-11e4-90ae-080027615026 |
+---------------+--------------------------------------+
1 row in set (0.00 sec)

###主库端查看从库的uuid
master_mysql> show slave hosts;
+-----------+------+------+-----------+--------------------------------------+
| Server_id | Host | Port | Master_id | Slave_UUID                           |
+-----------+------+------+-----------+--------------------------------------+
|        33 |      | 3306 |        11 | 62ee10aa-b1f7-11e4-90ae-080027615030 |
|        22 |      | 3306 |        11 | 6ac0fdae-b5d7-11e4-a9f3-0800278ce5c9 |
+-----------+------+------+-----------+--------------------------------------+
### Author : Leshami
### Blog   : http://www.php.cn/

4. Extension reference
a. Description of server_id
The server ID, used in replication to give each master and slave a unique identity. This variable is set
by the --server-id option. For each server participating in replication, you should pick a
positive integer in the range from 1 to 232– 1(2 32nd power minus 1) to act as that server's ID.

b、Description of server_uuid
Beginning with MySQL 5.6, the server generates a true UUID in addition to the --server-id
supplied by the user. This is available as the global, read-only variable server_uuid( Global read-only variable)

When starting, the MySQL server automatically obtains a UUID as follows:
a). Attempt to read and use the UUID written in the file data_dir/auto .cnf (where data_dir is
the server's data directory); exit on success.
b). Otherwise, generate a new UUID and save it to this file, creating the file if necessary.
The auto. cnf file has a format similar to that used for my.cnf or my.ini files. In MySQL 5.6,
auto.cnf has only a single [auto] section containing a single server_uuid [1992] setting and
value ;

##ImportantThe auto.cnf file is automatically generated; you should not attempt to write
or modify this file

Also beginning with MySQL 5.6, when using MySQL replication, masters and slaves know one another's UUIDs. The value of a slave's UUID can be seen in the output of SHOW SLAVE HOSTS. Once
START SLAVE has been executed (but not before), the value of the master's UUID is available on the
slave in the output of SHOW SLAVE STATUS.

In MySQL 5.6.5 and later, a server's server_uuid is also used in GTIDs for transactions originatingon that server. For more information, see Section 16.1.3, “Replication with Global Transaction

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