Spicerack already provides an authdns_servers accessor that returns a map from hostname to IP (along with its RemoteHosts equivalent, authdns_active_hosts).
This is used in a couple of places, including initializing the set of Resolver instances internal to dnsdisc.Discovery, and in its current form, returns a static set of hosts read from a puppet-managed config file.
In discussion on https://gerrit.wikimedia.org/r/1072612, @ssingh noted that it would be good to provide a way to exclude depooled authdns hosts in certain use cases, particularly ones asserting that resolution DNS returns an expected value - e.g., this was in the context of the sre.discovery.datacenter cookbook, but the same applies to Discovery.check_ttl or similar.
As a starting point, it would be good if Spicerack offered an accessor that returned only those authdns hosts that are (currently) pooled.
@ssingh pointed out some of the changes made in https://gerrit.wikimedia.org/r/1009539 as an example of how this might be done.
Beyond that, there's the question of where / how that should be wired into Discovery (for checks like those described above). In the ideal case, actually querying conftool would happen at time of use, rather than just prior to construction (e.g., for the benefit of long-running cookbooks that might work with a long-lived Discovery instance).