[Pdns-users] resource-limits metrics

[Otto Moerbeek]

On Sun, Oct 24, 2021 at 06:43:59PM +0200, Christoph via Pdns-users wrote:

> Hi Remi,
> 
> Remi Gacogne wrote:
> > This counter is increased when we encounter a network issue that does
> > not seem to be caused by the remote end but by a problem on our side,
> > like if the recursor runs out of file descriptors or if we don't have a
> > network route to contact a given IP address, for example.
> 
> Thank you for this description, this helps me digging deeper.
> 
> pdns_recursor_fd_usage shows values bellow 200 and the default file
> descriptor limit is at 16k, so file descriptors should not be the root cause
> if pdns_recursor_fd_usage show the used file descriptors.
> 
> I made a PR to add fd-usage to the docs:
> https://github.com/PowerDNS/pdns/pull/10888
> 
> and your description for resource-limits:
> https://github.com/PowerDNS/pdns/pull/10889
> 
> so this is answered in the docs when the next person asks the same
> question as I had.
> 
> 
> unrelated:
> 
> from the logs when Recursor starts:
> 
> pdns_recursor: Insufficient number of filedescriptors available for
> max-mthreads*threads setting! (16384 < 16409), reducing max-mthreads to 2044
> 
> With 8 threads and max-mthreads at the default value (2048)
> this should be:
> 2048 * 8 = 16384
> Are the extra 25 (16409-16384) the basics that recursor needs by default?
> 
> best regards,
> Christoph

Indeed, the recursor reserves FDs for other purposes as well. With the
upcoming 4.6.0 release this reserved number wil be bigger, since it
will take into account potential outgoing TCP connections (which can be
long living with that release) as well.

	-Otto