DoH cycling
With kresd 4.0.0 we've seen it occasionally slip into a loop consuming 100% CPU, becoming unresponsive. So far we've been unable to intentionally reproduce that, and apparently it would never happen with Firefox DoH as the client in combination with recent lua library versions on kresd side. So far it's very unclear what's the underlying problem.
Technical details [note to self]: the cqueues event loop got 100% busy with processing immediate actions, so even the concept of "time now" got never updated and other future events wouldn't be processed.