[Pdns-users] Using pdns-recursor on a network with high latency.

Sten Spans sten at blinkenlights.nl
Fri Sep 18 07:16:51 UTC 2009

On Wed, 16 Sep 2009, Andre Recnik wrote:

> Recently my ISP has been doing some 'upgrades' which as caused very high 
> latency in the last few days.  This latency is between 2.1 and 5.6 seconds 
> (as seen in a trace route to outside my network).
> As a result almost all look-ups are failing - and I have had to use BIND as 
> my recursor (which for some reason works even with the high latency).

This is indeed something that pdns-recursor doesn't handle very well.

> I'm assuming that there is a built in timeout system in pdns-recursor, and 
> that this is causing the lookups to fail - however I can't find a way to 
> change this value (at least not without source modification).
> Is there a config file option that would let me change the timeout (or number 
> of tries)?   Should that be added as a feature to future releases?   Or is 
> this perhaps the result of some other bug or feature in pdns-recursor?

As far as I know there currently is no way to improve powerdns-recursor's
behaviour, short of modifying the source. I think Bert would appreciate a 
well tested patch which improves the behaviour, although only if it doesn't
hurt lookup performance. It might be reasonable to add an "high-latency" 
option, or even better use the initial root-hints lookup and prehaps later 
ones to auto-tune a reasonable timeout value.

Sten Spans

"There is a crack in everything, that's how the light gets in."
Leonard Cohen - Anthem

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