[Pdns-users] pdns-recursor metrics review and tuning advice request

[Scott Crace]

 Hello all,
 Long time lurker on the message list and would like some performance
and/or tuning advice.
We've been using pdns-recursor as internal recursive nameservers for quite
some time now.
The original implementer of pdns departed and I was recently tasked with
replacing or upgrading all of the servers with newer RHEL9 versions. I
opted to build fresh and migrate the configuration to the latest 5.2
release.

I'm hearing occasional complaints about odd issues and/or clients cycling
through their DNS servers rapidly (timeouts?). Manual testing DNS works but
I am reading through the metrics and performance documentation. I am hoping
someone with a more experienced eye could take a look at a sampling of the
periodic statistics report (below) and provide some insight or
prioritization on any urgent issues I should focus on studying first.

My observations:
* I do note that the performance documentation talks about
firewalld/stateful firewalls impact but the legacy servers were using the
same basic setup. If the firewall is the problem is there a way to validate
this (other than stopping firewalld and waiting)?
* The "worker" threads seem evenly distributed to my novice eye and our qps
(queries per second) rate is low as I would expect since the name servers
are internal only resources.
* I ran a few pcaps and rec_control trace-regex for specific domain items
being reported as problematic. Everything seemed to be working with the
trace-regex always showing "Step3 Final resolve: No Error/6 or 8".

Thank you in advance for your time and consideration.

Sincerely,
Scotsie

```
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Periodic statistics
report" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.170"
cache-entries="23666" negcache-entries="497" questions="6831695"
record-cache-acquired="286931329" record-cache-contended="64414"
record-cache-contended-perc="0.02" record-cache-hitratio-perc="0.87"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Periodic statistics
report" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.170"
packetcache-acquired="16887684" packetcache-contended="1019"
packetcache-contended-perc="0.01" packetcache-entries="7112"
packetcache-hitratio-perc="37.75"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Periodic statistics
report" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.170"
edns-entries="38" failed-host-entries="50"
non-resolving-nameserver-entries="0" nsspeed-entries="968"
saved-parent-ns-sets-entries="65" throttle-entries="8"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Periodic statistics
report" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.170"
concurrent-queries="1" dot-outqueries="0" idle-tcpout-connections="0"
outgoing-timeouts="36594" outqueries="14668546"
outqueries-per-query-perc="214.71" tcp-outqueries="3131"
throttled-queries-perc="1.90"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Periodic statistics
report" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.170"
taskqueue-expired="0" taskqueue-pushed="540" taskqueue-size="0"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Queries handled by
thread" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.170"
count="3470098" thread="0" tname="worker"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Queries handled by
thread" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.170"
count="3360836" thread="1" tname="worker"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Queries handled by
thread" subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.171"
count="764" thread="2" tname="tcpworker"
Apr 17 16:07:28 nsrecdns01-1 pdns-recursor[1092]: msg="Periodic QPS report"
subsystem="stats" level="0" prio="Info" tid="0" ts="1744920448.171"
averagedOver="1800" qps="117"
```
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.powerdns.com/pipermail/pdns-users/attachments/20250418/a4db4873/attachment.htm>