[clue-tech] MySQL server reply packets delayed/lost under network congestion?

[David L. Anselmi]

Jim Ockers wrote:
> Whenever there is sustained high bandwidth network traffic over the PPP 
> link (such as downloading a large e-mail attachment, or streaming video) 
> the mysql connections all start to time out because response packets 
> from the server are not received at the client.  I observed this by 
> doing a simple "telnet server 3306" and observed that the MySQL banner 
> response with version number was delayed by several seconds or until the 
> bandwidth-hogging stopped.
> 
> What I don't understand is why I can still transfer data from other 
> servers on the Linux system, such as "net view \\server" and "dir 
> \\server\sharename" (using the Windows redirector to talk to Samba on 
> the Linux system).  Also the apache web server on the Linux system 
> responds normally, both from a web browser and also in response to 
> "telnet server 80" and then "GET / HTTP/1.0".

I assume that other services are delayed like the MySQL banner.  Most of 
what you tried though would use fairly small responses (one packet, 
even?) so maybe the MySQL protocol is more verbose.

It seems that clients have several timeouts available:

http://dev.mysql.com/doc/refman/5.1/en/mysql-options.html

Maybe the protocol takes too long in some cases.

Dave