MySQL Bugs: #58874: generic error given with failed queries

Bug #58874	generic error given with failed queries
Submitted:	10 Dec 2010 18:22	Modified:	23 Aug 2011 10:36
Reporter:	Lig Isler-Turmelle	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Enterprise Monitor: Agent	Severity:	S4 (Feature request)
Version:	all	OS:	Any
Assigned to:	Mark Leith	CPU Architecture:	Any

Description:
getting the error message:

(critical) agent_mysqld.c:512: [unix:/mysql/mysql/mysql.sock] mysql_real_query("SELECT value FROM mysql.inventory WHERE name = 'uuid'") failed: Lost connection to MySQL server during query (errno=2013)
Please GRANT SELECT ON mysql.inventory TO 'mysql_monitor'@'%';

Even with the correct permissions for the user.

When speaking with Oldag got this reply:

Dec 09 12:24:48 <oldag>	it doesn't look like we actually check for a permission error
Dec 09 12:24:53 <oldag>	and that is just a blanket message
Dec 09 12:24:58 <oldag>	2013 is anyone's guess
Dec 09 12:25:47 <oldag>	all we check is 
Dec 09 12:25:50 <oldag>		if (!(query_succeeded = agent_mysqld_query_raw(m, C(SELECT_UUID), 0))) {
Dec 09 12:26:09 <oldag>	then, 1146, table does not exist (we create it)
Dec 09 12:26:16 <oldag>	otherwise, generic permissions error message
Dec 09 12:26:19 <oldag>	even though here it was 2013
Dec 09 12:26:23 <oldag>	which is out of my league
Dec 09 12:26:46 <oldag>	so, the log message is lame.  you could write up a bug on that
Dec 09 12:26:57 <oldag>	"only suggest permission error if it is ding ding!  a permission error!"

So here I am asking for some better error messages when the query fails.

How to repeat:
na

Suggested fix:
for debugging purposes the more detailed the error message you can give the better.

The real problem is not just misleading message, but the fact that agent justcompletely shuts down (receiving 2013).

So, no further monitoring possible until manual restart if following occurs, e.g. when connection to monitored sever is not stable for some period of time:

1. Agent connection established to monitored mysql
2. But immediately got timeout querying mysql.inventory 
->
3. Agent will shutdown

2010-12-11 17:52:02: (critical) agent_mysqld.c:723: successfully connected to database at myhost.com:3308 as user myuser (with password: YES)
2010-12-11 17:52:32: (critical) agent_mysqld.c:512: [myhost.com:3308] mysql_real_query("SELECT value FROM mysql.inventory WHERE name = 'uuid'") failed: Lost connection to MySQL server during query (errno=2013)
Please GRANT SELECT ON mysql.inventory TO 'myuser'@'%';
This necessary for correct execution of the agent. 
Shutting down now.

Mark Leith writes: 
Patch pushed to 2.3.2:

1993 Mark Leith	2010-12-13
     Bug#58874 / EM-5093 - agent may shutdown after error 2013
     - Split out the error message as requested

Note that this does not implement retry logic in this case, if that is required, please open a separate issue for this.

Andy Bang writes: 
Fix is in build 2.3.2.2050.

Verified fixed on 2.3.2.2053

You now see on the agent log:

(critical) agent_mysqld.c:712: [127.0.0.1:5132] agent connecting to mysql-server failed: mysql_real_connect(host = '127.0.0.1', port = 5132, socket = ''): Lost connection to MySQL server at 'reading initial communication packet', system error: 54 (mysql-errno = 2013)
(critical) proxy-plugin.c.1612: Cannot connect, all backends are down.

Added to 2.3.2 changelog:

The Agent could die with a vague error message when encountering a
SQL error code 2013, requiring a manual restart.
The message is now more specific.

Thank you for your bug report. This issue has already been fixed in the latest released version of that product, which you can download at

  http://www.mysql.com/downloads/