MySQL Error Messages: MySQL server has gone away & Lost connection to server during query

‘MySQL server has gone away‘ and ‘Lost connection to server during query‘ MySQL error messages are one of the more common encountered with vBulletin forums. The main reason being non-optimal MySQL server settings – usually the default my.cnf values for MySQL are in use or setting the wait_timeout value too low.  A whole list of reasons for these MySQL error messages are listed here.

But the other day I came across another reason why these MySQL error messages may occur. If you run a control panel such as WHM / Cpanel, it has a set of default cronjobs which runs. One in particular is for /scripts/upcp which updates WHM/Cpanel versions and checks for version updates to components such as MySQL server.  One vB client, kept getting a handful of these MySQL server has gone away errors around the same time each morning starting at around 5:14 am.

Database error in vBulletin 3.8.6:
 
Invalid SQL:
 
SELECT postid, post.title, pagetext, post.threadid, thread.title AS threadtitle
FROM post AS post
INNER JOIN thread AS thread USING(threadid)
WHERE postid = 3160513;
 
MySQL Error   : MySQL server has gone away
Error Number  : 2006
Request Date  : Tuesday, March 15th 2011 @ 05:14:38 AM
Error Date    : Tuesday, March 15th 2011 @ 05:14:39 AM
Script        : http://forumdomain.com/forums/editpost.php?do=updatepost&p=3160513
Referrer      : http://forumdomain.com/forums/editpost.php?do=updatepost&p=3160513
IP Address    : xxx.xxx.xxx.xxx
Username      : mysqlusername
Classname     : vB_Database
MySQL Version :

Turns out the /script/upcp cronjob is scheduled to start running at 5:14 am each morning and it was the peak or busy vBulletin forum activity time. So the solution for MySQL error messages, was to change the scheduled cronjob time for /script/upcp to a time which was off peak for the forums.