Hi
The "MySQL server has gone away" error appens if a mysql connection exceeds "wait_timeout" or "max_allowed_packet".
http://dev.mysql.com/doc/refman/5.5/en/gone-away.html

Some config have small "wait_timeout" by default (600 seconds for mysql IUS rpm) so it flood zabbix_server.log for nothing (the "permanent" connection get kicked out, and so zabbix fail to use the connection)

Using mysql automatic reconnection allow the mysqlclient to try to reconnect once and if it fail again display the error.
http://dev.mysql.com/doc/refman/5.5/en/auto-reconnect.html

Attached is a small patch that add automatic reconnection for mysql (and clear the server log file from "spam")