Strange recursor response time pattern
matt at conundrum.com
Tue Sep 5 17:05:52 UTC 2017
On 5 September 2017 at 11:56, Havard Eidnes <he at uninett.no> wrote:
> some further local discussion has made me aware that us running
> "collectd" for monitoring BIND may be contributing to the
> problem; collectd fetches data each 10s by using the BIND-
> configured statistics-channel, thus BIND is processing a TCP
> connection to deliver the statistics data.
> It's still somewhat surprising and disappointing that this should
> interfere this much with DNS query processing...
> Is that pulling the old-style stats file, or the HTTP-based stats channel?
If the latter... the zone list (and by extension the root document) seems
to take a long time to process, and involves some sort of locking that
blocks all query processing while the list is being generated. We
encountered this on a 3+ million zone instance.. BIND would stop answering
queries for several minutes if anyone requested the root stats document or
the zone list.
As Ray says, you may be better off individually querying each of the other
documents and processing those rather than polling the root doc to get them
all in one shot.
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