On 16/11/2020 15:35, Eric Beck via Pdns-users wrote:
The recursor was still one .ca master zone file behind

I'm not sure what you mean by "one .ca master zone file behind". The recursor doesn't copy the zone file; it reads (and caches) individual records.

, even after
plenty of time had elapsed.

Can you show the actual output for "dig" against the recursor for the record in question?  The dig output should have shown a TTL, and that TTL should have been decrementing towards zero, after which it would have been refreshed from one of the authoritative servers for the domain.

Or were you getting NXDOMAIN for the query (for a newly-created domain?)  Negative answers are also cached. The .ca SOA record says they can be cached for one hour:

;; ANSWER SECTION:
ca.            3585    IN    SOA    prdpublish04.cira.ca. admin-dns.cira.ca. 2011161530 1800 900 3456000 *3600*


Any idea why this would happen?  Is there some setting that would result
in this sort of behaviour?

Most likely TTL, unless you can show evidence to the contrary. You can use rec_control dump-cache <https://doc.powerdns.com/recursor/manpages/rec_control.1.html> to dump the entire cache contents to disk.

Note: the PDNS recursor has multiple levels of cache, including a "packet cache" which is a shortcut when exactly the same query packet is seen again.

This can lead to some odd situations, where client A sees one answer repeatedly with a 'dig', but client B sees a different answer.  This can happen if client A and client B asked with different flags, so get mapped to different entries from the packet cache, and the authoritative answer changed between client A making the request and client B making the request.

But even those will resolve themselves when the record expires.

Regards,

Brian.

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