Investigate resolver hangs in Perflab
After #2401 (closed)/!4601 (merged) got merged, recursive tests in Perflab started triggering what looks like hangs in the new resolver code:
- https://perflab.isc.org/#/config/run/5bf195dd83ba91a870b2976f/
- https://perflab.isc.org/#/config/run/5cd6a166643076f6c1f6c26f/
- https://perflab.isc.org/#/config/run/5db74b6264458967f762143a/
- https://perflab.isc.org/#/config/run/5db74b7264458967f762143b/
- https://perflab.isc.org/#/config/run/5db74c2764458967f7621440/
- https://perflab.isc.org/#/config/run/5db74c3464458967f7621441/
This was already pointed out on Mattermost. What seems to be happening is that during the recursive tests in Perflab, the tested resolver only responds to queries for a few (dozen) seconds and then stops responding indefinitely. Such failure modes were not observed in AWS-based resolver benchmarks.
We should definitely get to the bottom of what is happening here.