[Pdns-users] Intermittent SERVFAIL Response

Federico Olivieri lvrfrc87 at gmail.com
Tue Aug 18 16:42:14 UTC 2015

Hi All,

I have the same problem and it happens random for some well known domains.

As far as I m concern I saw mainly when I have peak of request and also if
you query the same domain after get SERVERFAIL, I m able to get the right

Just a question from my side, when you say 4 thread you mean with 4 DNS
server in parallel?
On 18 Aug 2015 17:14, <sthaug at nethelp.no> wrote:

> > I'm running PowerDNS Recursor 3.7.3 on a pair of Ubuntu 14.04.3 LTS
> servers.
> > I'm getting intermittent SERVFAIL responses on both servers to queries
> for a
> > particular name. Could someone please help me understand what might be
> > causing these failures? Here are examples of the SERVFAIL responses I'm
> > seeing on one of the servers:
> >
> > $ dig @localhost www.concoursmustang.com any
> I've seen similar problems (intermittent SERVFAIL) for various domains.
> My conclusion after investigating these is that PowerDNS recursor does
> not have a coherent cache - and you might be hitting different threads,
> one or more of which answer SERVFAIL. You may be able to clear the
> problem with "rec_control wipe-cache <domain>". Restarting also works,
> of course - but throws away the cache.
> (We're running with threads=4 in recursor.conf and can easily see the
> incoherent cache by simply repeating the same query multiple times and
> noting the TTL in the answers. With a coherent cache you'd expect the
> TTL to always count down (until 0, of course). With PowerDNS Recursor
> the TTL is inconsistent - sometimes *increasing*. I assume it is
> perfectly consistent within one thread.)
> Steinar Haug, AS 2116
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