[Pdns-users] Strange behaviour of recursor cache on a particular domain

[GAVARRET, David]

Hi all,

I have strange results when I query my recursors (official release
3.1.1) about the domain melusine.eu.org.

~$ dig +noall +answer melusine.eu.org ns
melusine.eu.org.        20084   IN      NS      ns.melusine.eu.org.
melusine.eu.org.        20084   IN      NS      ns.eu.org.

On the authoritative servers, an 'A' record has been modified on the
root of the domain more than 2 weeks ago :
~$ dig +noall +answer @ns.melusine.eu.org melusine.eu.org soa
melusine.eu.org    
melusine.eu.org.        21600   IN      SOA     ns.melusine.eu.org.
hostmaster.melusine.eu.org. 2006060701 7200 3600 1209600 259200
melusine.eu.org.        21600   IN      A       193.55.139.7

But my recursors don't have the same informations. Some still have the
previous A record value (195.6.210.105), some others have both the old
and the new one ... but they all give the same (and the last) serial
number for the SOA :

~$ dig +noall +answer @ns0  melusine.eu.org soa melusine.eu.org
melusine.eu.org.        21486   IN      SOA     ns.melusine.eu.org.
hostmaster.melusine.eu.org. 2006060701 7200 3600 1209600 259200
melusine.eu.org.        97276   IN      A       195.6.210.105
...
~$ dig +noall +answer @ns3 melusine.eu.org soa melusine.eu.org
melusine.eu.org.        21497   IN      SOA     ns.melusine.eu.org.
hostmaster.melusine.eu.org. 2006060701 7200 3600 1209600 259200
melusine.eu.org.        138386  IN      A       195.6.210.105
melusine.eu.org.        10358   IN      A       193.55.139.7
~$ dig +noall +answer @ns4 melusine.eu.org soa melusine.eu.org
melusine.eu.org.        21600   IN      SOA     ns.melusine.eu.org.
hostmaster.melusine.eu.org. 2006060701 7200 3600 1209600 259200
melusine.eu.org.        90743   IN      A       195.6.210.105
...
~$ dig +noall +answer @ns9 melusine.eu.org soa melusine.eu.org
melusine.eu.org.        21600   IN      SOA     ns.melusine.eu.org.
hostmaster.melusine.eu.org. 2006060701 7200 3600 1209600 259200
melusine.eu.org.        115956  IN      A       195.6.210.105
melusine.eu.org.        16493   IN      A       193.55.139.7

This zone has been modified several times, with a superior serial number
each time (the owner claims ...).
I must precise that I use the max-cache-entries setting (=7000000) on my
servers. 
Is there any specific handling of zone refresh when a limit is set for
the cache ?

Regards,
-- 
David Gavarret