[dnsdist] Unexpected not-caching behavior in 1.5.0-rc3

[Remi Gacogne]

Hi Phillip,

On 7/1/20 6:57 PM, Phillip R. Jaenke via dnsdist wrote:
> To test/evaluate performance, one of the tests I run is basically "look
> up a consistent group of records I know exist, then do it a couple
> hundred more times or so." Some from the local authoritative, some from
> the Internet at large. The corresponding dnsdist configuration looks
> like this:
> [...]
> Given this config my expectation would be that lookups of these would
> get cached on the first hit of the performance run, and then dnsdist
> would go to cache. But that's not happening - instead it's forwarding
> every query to the pool and insisting it's a 100% miss rate over tens of
> thousands of queries where there's actually only about 200 -unique-
> questions and the responses are consistent.

Would you be able to describe the queries you are sending and how you
are sending them? The first thing that comes to mind is that you are
using a tool which adds EDNS0 Cookies to queries. dnsdist's packet cache
currently hashes the whole packet, cookies included, and that results in
a different entry for every cookie value, as described in [1]. We
planned on addressing this in 1.6.0 [2].

[1]: https://github.com/PowerDNS/pdns/issues/5131
[2]: https://github.com/PowerDNS/pdns/pull/8993

Best regards,
-- 
Remi Gacogne
PowerDNS.COM BV - https://www.powerdns.com/

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