From: Ben Clewett
Date: July 29 2005 2:33pm
Subject: Re: Complete server lock
List-Archive: http://lists.mysql.com/mysql/187090
Message-Id: <42EA3E24.50309@clewett.org.uk>
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Jigal,

Thanks.

I can confirm that there were no domains used for our permissions.  All 
IP based.  Although this may have been the cause, I don't think it was 
in this case.  I think as well that DNS timeouts are in the region of 20 
seconds to 2 minutes.

Would any person know if there is any other part of MySQL which uses DNS 
lookups?  For instance, logging of some kind?

Or any other reason a MySQL daemon would not respond to a kill?

Thank for the ideas,

Ben Clewett.


Jigal van Hemert wrote:
> Ben Clewett wrote:
> 
>> It had been suggested that our DNS failed prior to this event.  I 
>> don't think MySQL uses DNS, but I am not entirely sure.
> 
> 
> If the db, user, etc. tables in the mysql system database (containing 
> privileges, etc.) contain host names instead of IP-addresses I suspect 
> it needs a DNS to resolve these...
> 
>> If I get a state where a 'kill' will not cause MySQL to exit.  Is 
>> there any other know way to ask MySQL to exit cleanly?
> 
> 
> MySQL server was probably waiting for a bunch of DNS requests? Until a 
> timeout occurs it will probably keep the connection waiting. This can 
> cause a lot of connections to occur until you reach max_connections at 
> which point it will not accept new connections anymore.
> 
> Regards, Jigal.
>