[dns-operations] sophosxl.net problem?

Florian Weimer fweimer at redhat.com
Tue Nov 12 13:30:00 UTC 2019

* James Stevens:

> Health-checks (e.g. pingdom etc) with RD=1 seem pretty common.

They do not work reliably because failure rates for some large
authoritative servers with RD=1 are significantly higher than with RD=0
(or at least were about ten years ago).  I remember a bug in monitoring
software which reported sporadic failure for perfectly healthy servers,
and it turned out that the cause was a bug where the software sent RD=1
queries instead of RD=0 queries.  The failure was stochastic, though.
It oculd have been software or configuration divergence a cluster behind
a load balancer But if I recall correctly, the failure rate was quite a
bit lower than that, so there was probably another factor involved.


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