Environment:
RHEL 5 servers, MySQL 5.1.43, PHP 5.1.6 (using MySQLi).
Currently only available within our internal VPN network.

Servers
ServerA: Webserver
ServerB/C/D: Database server (1 master 2 slaves)

The error (on ServerA)
[Tue May 25 11:12:17 2010] [error] [client CLIENTIP] PHP Warning: mysqli::real_connect() [function.mysqli-real-connect]: (HY000/2003): Can't connect to MySQL server on 'ServerB' (4) in /home/**/Database.php on line 67, referer: [website]

Problem description
It appears that at completely random times, our website is unable to connect to one of the MySQL servers - usually the Master. Except for the forementioned error message, there is nothing to be found in any of the logs as far as I can see, and most of the times the connection is succesful and everything works as it should. It's just at completely random times, this error pops up.

Herhangi bir iç trafiği engelleme hiçbir güvenlik duvarı yok, zaman aşımı değeri 3 ama bağlanamıyor önce 3 saniye sürmüyor. Varsayılan mysql istemcisi ile ben ServerB, C ve D ServerA bağlanabilir ve henüz bir sorunla karşılaşmadım.