RE: DNS lookup problems after upgrade from Etch to Lenny
> From: Stackpole, Chris [mailto:CStackpole@barbnet.com]
> Sent: Monday, June 15, 2009 4:30 PM
> Subject: DNS lookup problems after upgrade from Etch to Lenny
>
> Hey guys,
>
> I have been trying my best to figure this out recently but not having
> much luck. I am hoping someone here might be able to help.
>
> We had an Etch box that had been running great for almost 2 years.
When
> we decided that we really should upgrade to Lenny, the box had over
300
> days of uptime. It was a really solid box that handled a ton of data
for
> us.
>
> There are a number of reasons, but we needed to update the system. So
I
> ran the upgrade process. I did an `apt-get update` and `apt-get
upgrade`
> on Etch, restarted, changed out sources to Lenny then did an `apt-get
> dist-upgrade`. Standard and simple and everything seemed to go really
> well.
>
> However, shortly after, it started slamming our DNS servers. It went
> from an average of 3.5 requests per minute to over 7000 requests per
> minute. Every time it talks to a system, it does a DNS lookup.
Scratch that bit. My network guy just sent me the official numbers. It
jumped from 3.5 requests per minute to 73,955.25 requests per minute. A
factor of 10 worse. :-0
>
> At first I thought it was Apache and or the applications we run, but
> after some testing, I don't think that is the case. I stopped all the
> programs and apache before I started pinging other systems by their
> domain name. It constantly asked the DNS for information.
>
> How do I know? I am running `tshark -f 'port 53'` and watching all the
> data in real time. When I ping a name, it does a lookup. If I leave
the
> ping running, after a few seconds it asks again. I set up a loop using
> `ping -c1` and no matter how fast the loop ran, it asked for the name
> every time.
>
> So a busy server working with ~50 other computers and tons of
> connections is asking the DNS for every connection!
>
> Can any one help out? I am digging around in all sorts of conf files
but
> not finding anything. My search online seems to suggest I should
install
> a DNS caching utility, but I don't understand why I have this problem.
I
> didn't have it before and on another system running a fresh build of
> Lenny running the exact same software handling a similar load and its
> DNS ask rate is just as low as it was on this system running Etch.
>
> I am at a loss. I appreciate any help people can give.
>
> Thanks,
> Chris Stackpole
>
>
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