[Pdns-users] pdns-recursor (4.6) empty response after expiration of the TTL of the cached record

[Leeflangetje]

Hi,

Since we upgraded to pdns-recursor 4.6 we sometimes experience some
weird behaviour with queries via pdns-recursor.

Sometimes, when a previously queried record expires through it's TTL,
the recursor does not provide an answer anymore, until it's restarted.

Unfortunately I am not able to reproduce this. It happens occasionally.
When it happens, we see this: 

Faulty server:

dig @ns1 riecis.nl A

; <<>> DiG 9.11.36-RedHat-9.11.36-3.el8 <<>> @ns1 riecis.nl A
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27148
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;riecis.nl.         IN  A

;; AUTHORITY SECTION:
riecis.nl.      2828    IN  SOA ns1.minvenj.nl. hostmaster.solvinity.com. 2022010301 1800 300 604800 3600

;; Query time: 2 msec
;; SERVER: xxx.xxx.xxx.xxx#53(xxx.xxx.xxx.xxx)
;; WHEN: Tue Sep 20 12:16:55 CEST 2022
;; MSG SIZE  rcvd: 110

other server:

dig @ns2  riecis.nl A

; <<>> DiG 9.11.36-RedHat-9.11.36-3.el8 <<>> @ns2 riecis.nl A
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61517
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;riecis.nl.         IN  A

;; ANSWER SECTION:
riecis.nl.      224 IN  A   159.46.204.40

;; Query time: 1 msec
;; SERVER: xxx.xxx.xxx.xxx#53(xxx.xxx.xxx.xxx)
;; WHEN: Tue Sep 20 12:17:03 CEST 2022
;; MSG SIZE  rcvd: 54


We have a fairly simple configuration, just on what address and port to
 listen on, to use the same address for outgoing queries, en a short li
st of addresses that are allowed to query.

I have confirmed this problem upto and including version 4.6.3

Anyone an idea on how to approach this matter?

Regards



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