> 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 _______________________________________________ Pdns-users mailing list [email protected] http://mailman.powerdns.com/mailman/listinfo/pdns-users
