MHA集羣報錯：The slave I/O thread stops because master and slave have equal MySQL server UUIDs
實驗環境
操作系統：CentOS Linux release 7.3.1611 (Core)
數據庫系統： MySQL 5.7.19
問題重現
在虛擬機上配置MySQL的MHA集羣時，在配置主從複製模式的時候發現配置失敗：
mysql> show slave status\G;
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.
問題分析
問題提示主從使用了相同的server UUID，一個個的檢查：
檢查主從server_id
主庫：
mysql> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id | 1 |
+---------------+-------+
1 row in set (0.01 sec)
從庫：
mysql> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id | 2 |
+---------------+-------+
1 row in set (0.01 sec)
server_id不一樣，排除。
檢查主從狀態：
主庫：
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 154 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
從庫：
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 306 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
File一樣，排除。
最後檢查發現他們的auto.cnf中的server-uuid是一樣的。。。
[root@localhost ~]# vim /var/lib/mysql/auto.cnf
[auto]
server-uuid=4f37a731-9b79-11e8-8013-000c29f0700f
問題解決
停止從庫的mysqld服務，刪除他的auto.cnf文件，再啓動數據庫服務即可：
[root@localhost mysql]# systemctl stop mysqld.service
[root@localhost mysql]# mv /var/lib/mysql/auto.cnf /var/lib/mysql/auto.cnf.bak
[root@localhost mysql]# systemctl start mysqld.service
此時再去查看從庫auto.cnf，已自動生成新的server-uuid：
[root@localhost mysql]# vim /var/lib/mysql/auto.cnf
[auto]
server-uuid=2682888d-994a-11e8-aaf0-000c298cdafc
再查看從庫狀態，已正常
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.232.128
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 1208
Relay_Log_File: localhost-relay-bin.000003
Relay_Log_Pos: 1374
Relay_Master_Log_File: mysql-bin.000001
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: 1208
Relay_Log_Space: 1585
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: 1
Master_UUID: 574ce30b-9637-11e8-b98b-000c29e7e754
Master_Info_File: /var/lib/mysql/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:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
ERROR:
No query specified
原理分析
我搭建集羣是先在虛擬機上搭好主庫環境，然後直接克隆鏡像當作從庫，這樣會導致主從庫生成相同的server-uuid。只需刪除一個server-uuid並重啓數據庫服務即可解決問題。
下面附上官網對於相關配置的描述：
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(全局只讀變量)
When starting, the MySQL server automatically obtains a UUID as follows:
1. 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.
2. 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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原文：https://blog.csdn.net/sunbocong/article/details/81634296