[dnsdist] Healthchecks at startup

[Marki]

Hello,

I have an issue here with a (potential) cyclic dependency that I'd like 
to solve.

So our clients are pointed at dnsdist, obviously.

Based on the query, dnsdist sends the query to internal NSes, or 
external recursive resolvers.

Now the issue is the healthcheck of internal NSes at startup (resolution 
of DNS Root A): When starting up the entire thing (both named and 
dnsdist), sometimes dnsdist shows one of the local resolvers - namely 
the one running on the same node as dnsdist as down.

This is because the internal resolvers have a forwarder to dnsdist to be 
able to resolve anything external (necessary in case a stub resolver 
would ask to resolve e.g. a local CNAME pointing to an external domain). 
So probably dnsdist is not entirely ready yet (external NS healtcheck 
not ready at that millisecond or sth else).

I'd like that initial healthcheck to preferably succeed immediately. Is 
there a way to maybe define some backends as dependencies of others? Or 
any spontaneous design thoughts.... ;)

Thanks
Marki