Fatal error: Connecting to MySQL server 'localhost' failed.

You get more information about the problem in our knowledge base: http://www.woltlab.com/help/?code=2002

Information:

error message: Connecting to MySQL server 'localhost' failed.
error code: 2002
sql type: MySQLDatabase
sql error: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (11)
sql error number: 2002
sql version:
file: /var/www/clients/client1/web46/web/wcf/lib/system/database/MySQLDatabase.class.php (29)
php version: 5.3.10-1ubuntu3.15
wcf version: 1.0.11 pl 4 (Horizon)
date: Tue, 03 Mar 2015 00:30:01 +0000
request: /index.php?page=Thread&postID=31212
referer:

Stacktrace:

#0 /var/www/clients/client1/web46/web/wcf/lib/system/database/Database.class.php(76): MySQLDatabase->connect()
#1 /var/www/clients/client1/web46/web/wcf/lib/system/WCF.class.php(270): Database->__construct(...)
#2 /var/www/clients/client1/web46/web/wcf/lib/system/WCF.class.php(88): WCF->initDB()
#3 /var/www/clients/client1/web46/web/global.php(18): WCF->__construct()
#4 /var/www/clients/client1/web46/web/index.php(7): require_once('/var/www/client...')
#5 {main}