Re: Complete server lock

[JamesDR]

Ben Clewett wrote:
> 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.
>>
> 
> 
I noticed, on my Linux server, that MySQL makes a DNS lookup anyway. 
Even if the IP is used or not. It normally digs on the PTR record. I had 
all of my perms IP based, however, it still looked at the PTR record. At 
the time I hadn't set any up in my DNS server. After I added all the PTR 
records of the clients that were connecting to the server, it was fast 
again.

...Something to think about...

-- 
Thanks,
James