[Pdns-users] servfail-packets>0 but no data in servfail-queries ring buffer

[Martin Kellermann]

hi,

pdns auth server 4.1.6 with postgresql backend

i'm facing the fact, that today the servfail-packets counter increased from 0 to 1.
https://doc.powerdns.com/authoritative/performance.html#servfail-packets tells me, that this is due to a database problem.
https://doc.powerdns.com/authoritative/performance.html#ring-buffers tells me that the servfail-queries ring-buffer shows which queries have been causing servfails.
but when i look at this ring-buffer (server:8081/?ring=servfail-queries) there are no entries - it's empty.

can someone please explain, what am i missing or not understanding correctly?

btw: i still can't figure out, how to get the ring-buffer entrys through API... 
see: https://mailman.powerdns.com/pipermail/pdns-users/2019-February/025758.html

thanks!

Regards

MK