The slave I/O thread stops because master and slave have equal MySQL server UUIDs

The slave I/O thread stops because master and slave have equal MySQL server UUIDs; these UUIDs must be different for replication to work.

問題原因：

replication 架構中需要保證每個 mysql 例項 UUID(UUID 儲存在 datadir 目錄下的 auto.cnf 檔案中 ) 唯一，就跟 server_id 一樣需要保證主從架構中所有 mysql 例項 server_id 唯一。之所以出現會出現這樣的問題，是因為我的從庫主機是克隆的主庫所在的主機，所以 auto.cnf 檔案中儲存的 UUID 會出現重複 (server_id 已經在 my.cnf 檔案中修改過 )

問題解決

關於該問題的解決方案其實很簡單，停掉備庫例項，刪除備庫 data 資料夾下的的 auto.cnf （ Windows 下檔名為 auto ） 檔案，啟動備庫例項，此時備庫就會產生一個新的 auto.cnf 檔案 ( 產生新的 UUID) 。

最近在部署MySQL主從複製架構的時候，碰到了"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." 這個錯誤提示。即主從架構中使用了相同的UUID。檢查server_id系統變數，已經是不同的設定，那原因是？接下來為具體描述。

1、錯誤訊息
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、檢視主從的server_id變數
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    |
+---------------+-------+
-- 從上面的情形可知，主從mysql已經使用了不同的server_id

3、解決故障
###檢視auto.cnf檔案
[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 ###從上的uuid，果然出現了重複，原因是克隆了虛擬機器，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  ###重新命名該檔案
[root@dbsrv2 ~]# service mysql restart          ###重啟mysql
Shutting down MySQL.[  OK  ]
Starting MySQL.[  OK  ]
[root@dbsrv2 ~]# more /data/mysqldata/auto.cnf  ###重啟後自動生成新的auto.cnf檔案，即新的UUID
[auto]
server-uuid=6ac0fdae-b5d7-11e4-a9f3-0800278ce5c9

###再次檢視slave的狀態已經正常
[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

###主庫端檢視自身的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)

###主庫端檢視從庫的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.linuxidc.com

4、延生參考
a、有關server_id的描述
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的32次方減1) to act as that server's ID.

 

b、有關 server_uuid的描述
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 (全域性只讀變數)

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;   

Important
The 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 originating
on that server. For more information, see Section 16.1.3, “Replication with Global Transaction

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