[Pdns-users] pdns recursor: forward-zones: load balancing and failover

[Otto Moerbeek]

On Tue, Oct 27, 2020 at 08:32:29PM +0300, Egor Fatyushin via Pdns-users wrote:

> Hello,
> I have two authoritative DNS servers and I'd like to use them as two
> replicas with the same set of records. Can I use 'forward-zones' for both
> failover and load balancing features.
> 
> I mean, if I have /etc/pdns-recursor/recursor.conf like this:
> ...
> forward-zones=aaa.zone.org=10.111.111.111:53;10.111.111.222:53
> forward-zones+=bbb.zone.org=10.111.111.111:53;10.111.111.222:53
> ...
> Can I configure the pdns recursor somehow to ask 10.111.111.111
> and 10.111.111.222 in a round robin way?

Nope, but see below.

> 
> BTW what is the default way to forward queries to multiple servers using
> forward-zones? I was trying to find it out searching pdns' code but without
> success:
> https://github.com/PowerDNS/pdns/search?p=2&q=forward-zones&type=code
> I thought pdns asks the second DNS if the first one doesn't reply, but if I
> stop the first DNS service, pdns responds with cached IPs (in case of cache
> hit) or with SERVFAIL (in case of cache miss). And I don't see any queries
> in the second DNS logs as well.

Exact behaviour depends on version.  Recent recursor (starting with
4.2 iirc) should probe both an pick the fastest and reprobe once in a
while. If that does not happen, please create a github issue providing
all the details.

	-Otto