Possible MySQL server UUID duplication for server



## Such an event occurs during the mysql enterprise monitor monitoring process. Topic: Possible MySQL server UUID duplication for server event. From the description of the prompt, it seems that there are duplicates. uuid, but in fact there is no duplicate uuid in the master-slave relationship. The master-slave relationship is built through xtrabackup. So what's the problem? The following is a description of the problem that causes duplicate uuid in monitoring when copying based on xtrabackup.

1. Fault phenomenon

Topic: Possible MySQL server UUID duplication for server afd6bca4-6636-11e3-9d60-74867ae1c47c: NOTICE
Categories:Monitoring and Support Services 
Current State:Open
Auto-Closes by Default:Yes
Advisor:Duplicate MySQL Server UUID 
Current Status:Notice
Last Checked:May 4, 2015 2:18:02 PM

prompts uuid changed N times, these two host configurations will appear in the MySQL Instances monitoring session In constant switching

MySQL server afd6bca4-6636-11e3-9d60-74867ae1c47c changed its hostname 181 times between the following hostnames:DBSRV-TXT01DBSRV-SLAVE02
MySQL server afd6bca4-6636-11e3-9d60-74867ae1c47c changed its connection TCP properties 96 times between the following TCP properties:
127.0.0.1:3306127.0.0.1:3307
AdviceCheck that you are not monitoring more than one instance with the following server UUID: afd6bca4-6636-11e3-9d60-74867ae1c47c. 
This can be caused by server or host cloning. If this is expected (example: HA scenarios), then please ignore this notice.

##2. Verification uuid
As described in the Google article, mysql.inventory saves the uuid information used by mysql enterpirse moitor monitoring

View the main library uuid and mysql.inventory table

[root@DBSRV-TXT01 ~]# mysql -uroot -p -e "
show variables like 'server_uuid';
select * from mysql.inventory;" -S /tmp/mysql3307.sock 
Enter password: 
+---------------+--------------------------------------+
| Variable_name | Value                                |
+---------------+--------------------------------------+
| server_uuid   | 1ed85852-dd27-11e4-aa4a-44a8420ba7a5 |
+---------------+--------------------------------------+
+--------+-------------------------------------------------------+
| name   | value                                                 |
+--------+-------------------------------------------------------+
| uuid   | afd6bca4-6636-11e3-9d60-74867ae1c47c                  |
| hostid | ssh:{8a:c7:a9:42:3a:6b:06:ad:fa:ed:04:ac:a5:fa:f0:b5} |
+--------+-------------------------------------------------------+

##View from the database The uuid and mysql.inventory table

[root@DBSRV-SLAVE02 ~]# mysql -uroot -p -e "    ---Author : Leshami
> show variables like 'server_uuid';            ---Blog   : 
http://www.php.cn/
> select * from mysql.inventory;"
Enter password: 
+---------------+--------------------------------------+
| Variable_name | Value                                |
+---------------+--------------------------------------+
| server_uuid   | f7e00194-2f59-11e4-bcf6-b82a72d46b21 |
+---------------+--------------------------------------+
+--------+-------------------------------------------------------+
| name   | value                                                 |
+--------+-------------------------------------------------------+
| uuid   | afd6bca4-6636-11e3-9d60-74867ae1c47c                   |
| hostid | ssh:{8a:c7:a9:42:3a:6b:06:ad:fa:ed:04:ac:a5:fa:f0:b5} |
+--------+-------------------------------------------------------+

## from above The query results show that the mysql.inventory table does contain the same uuidThis same uuid is due to the use of instance-level hot standby, so the two instances have the same uuid

Clear mysql.inventory, and then restart the monitoring agent (omitted), the problem is solved

[root@DBSRV-SLAVE02 ~]# mysql -uroot -p -e "truncate table mysql.inventory" -S /tmp/mysql3307.sock
Enter password:

3. About MySQL MEM UUID duplication

• MySQL Enterprise Monitor uses a number of unique values known as       
  UUIDs to identify the different      
  components, including the MySQL instance being monitored. UUID      
  values related to the MySQL instance and the host on which it runs      
  are stored in a table mysql.inventory within      
  the instance. MySQL Enterprise Monitor creates this table if it does not exist      
  already.

  Each MySQL Server has a UUID, stored in the
mysql.inventory
• table, that uniquely identifies the MySQL server to the rest of MEM. The server UUID is used to collate information about a single MySQL instance.

  Each host (the machine on which the agent is running) has a UUID to uniquely identify the host to the rest of MySQL Enterprise Monitor. This is used to collate the OS information (such as CPU, RAM and disk data). The host ID also determines whether the MySQL server is on the same host as it was before, to identify when data has been moved between machines, or when a machine has been upgraded . The host UUID is stored within the hostid

  row within the
mysql.inventory
• table.
  Each agent has a UUID to identify the agent to MEM. The agent UUID is defined within the
agent-uuid

parameter within the agent configuration file.

These UUIDs are used in combination to register and collate information, and to determine the location and source of an issue.

Note

Because each host must be unique, be careful when restoring from a backup so you do not have hosts with duplicated SSH keys or UUIDs.##The MySQL Enterprise Monitor Agent and MySQL Enterprise Service Manager use the unique host ID, stored within the

mysql.inventory### table on the monitored MySQL Server , to determine whether the instance being monitored is a clone. The host ID of the current server is checked against the stored value when the agent starts. If the generated host ID and stored host ID do not match, you get an error similar to the following in the agent log file:###

%s: [%s] the hostid from mysql.inventory doesn't match our agent's host-id (%s != %s)
We assume that this is a cloned host and shutdown now.
Please TRUNCATE TABLE mysql.inventory on this mysql-instance and restart the agent.
If this is a master for replication, please also run SET SQL_LOG_BIN = 0; first.

To fix the problem, connect to the MySQL server using the credentials configured when you installed the agent, and then truncate the mysql.inventory table:

mysql> TRUNCATE mysql.inventory;

Now restart the agent, which recreates the           mysql.inventory table with the updated          instance UUID and hostid information.

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