[CWB] mysql cache errors occurring recently

[Jörg Knappen]

We run a cqpweb on Ubuntu 14.04 LTS using the following php version


PHP 5.5.9-1ubuntu4.24 (cli) (built: Mar 16 2018 12:41:43)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
     with Zend OPcache v7.0.3, Copyright (c) 1999-2014, by Zend Technologies


and the mysql version

mysql  Ver 14.14 Distrib 5.5.59, for debian-linux-gnu (x86_64) using  
readline 6.3

We did not change cqpweb recently, nor did we anything but doing  
reqular system upgrades using
apt-get upgrade.

HOwever, when we try a frequency breakdown, the following error  
appears (frst encountered about a week or so ago):

CRITICAL ERROR - DATABASE CACHE OVERLOAD!





CQPweb tried to clear database cache space but failed!





Please report this error to the system administrator.


PHP debugging backtrace

array(5) {
   [1]=>
   array(4) {
     ["file"]=>
     string(35) "/var/www/html/cqpweb/lib/db.inc.php"
     ["line"]=>
     int(581)
     ["function"]=>
     string(20) "exiterror_dboverload"
     ["args"]=>
     array(0) {
     }
   }
   [2]=>
   array(4) {
     ["file"]=>
     string(35) "/var/www/html/cqpweb/lib/db.inc.php"
     ["line"]=>
     int(95)
     ["function"]=>
     string(16) "delete_saved_dbs"
     ["args"]=>
     array(0) {
     }
   }
   [3]=>
   array(4) {
     ["file"]=>
     string(42) "/var/www/html/cqpweb/lib/breakdown.inc.php"
     ["line"]=>
     int(160)
     ["function"]=>
     string(9) "create_db"
     ["args"]=>
     array(6) {
       [0]=>
       &string(4) "sort"
       [1]=>
       &string(10) "fqa49mvvxx"
       [2]=>
       &string(12) "[word="des"]"
       [3]=>
       &string(0) ""
       [4]=>
       &string(0) ""
       [5]=>
       &string(0) ""
     }
   }
   [4]=>
   array(4) {
     ["file"]=>
     string(41) "/var/www/html/cqpweb/lib/redirect.inc.php"
     ["line"]=>
     int(73)
     ["args"]=>
     array(1) {
       [0]=>
       string(42) "/var/www/html/cqpweb/lib/breakdown.inc.php"
     }
     ["function"]=>
     string(7) "require"
   }
   [5]=>
   array(4) {
     ["file"]=>
     string(37) "/var/www/html/cqpweb/exe/redirect.php"
     ["line"]=>
     int(1)
     ["args"]=>
     array(1) {
       [0]=>
       string(41) "/var/www/html/cqpweb/lib/redirect.inc.php"
     }
     ["function"]=>
     string(7) "require"
   }
}

and after a few more tries we finally reach the following error:

Too many database processes!

There are already 5 query sort databases being compiled.

Please use the Back-button of your browser and try again in a few moments.

Rebooting the server removes the latter error, but not the cache problem.

What can be the cause of the cache problem and how can I remove it?

Greetings from Saarbrücken,

Jörg Knappen