[Pdns-users] Occasional TCP query timeouts.

[Peter van Dijk]

Hello Grant,

I was hoping for a somewhat smaller capture. Hints about where in this capture the issue occurs are welcome :)

Kind regards,
Peter van Dijk

On Oct 5, 2011, at 2:16 AM, Grant Keller wrote:

> Here are the pcaps from the server in question.
> 
> ftp://ftp.sonic.net/pub/users/gkeller/tcp_pcap
> 
> Thank you for your help so far.
> 
> 
>> Hello Grant,
>> 
>> On Sep 30, 2011, at 7:12 PM, Grant Keller wrote:
>> 
>>> We have been having this problem with TCP queries timing out on one of our nameservers running pdns 3. We have a monitor that runs every two minutes, and every half hour or so it times out on its query. I can reproduce this by  running the following:
>>> 
>>> while [ 1 ]; do
>>> dig schwer.us +recurse +tcp +short +time=1 +retry=1 @c.ns.sr.sonic.net
>>> date
>>> sleep 1
>>> done
>>> 
>>> If I let that run for a while, it will capture several timeouts:
>>> 
>>> ;<<>>  DiG 9.7.3<<>>  schwer.us +recurse +tcp +short +time=1 +retry=1 @c.ns.sr.sonic.net
>>> ;; global options: +cmd
>>> ;; connection timed out; no servers could be reached
>>> 
>>> The pdns.log has no significant entries at the times that this occures. I have watched iptraf as I recieve the timeouts, and It dosn't seem that we are hitting our max number of tcp connections (1000). This problem first started in pdns-2.9.22, and continued after the upgrade. None of our other name servers have this problem.
>>> 
>>> What would be the next step in troubleshooting this? Are there any extra logging options I can turn on? Thanks in advance.
>> 
>> Most important to know, of course, is whether the queries even reach pdns. Are you in a position to run tcpdump/tshark on c.ns.sr.sonic.net, to monitor requests from a test run like the one described above?
>> 
>> Kind regards,
>> Peter van Dijk
> 
> 
> 
> -- 
> Grant Keller
> 
> 
> _______________________________________________
> Pdns-users mailing list
> Pdns-users at mailman.powerdns.com
> http://mailman.powerdns.com/mailman/listinfo/pdns-users