How to log individual upstream DNS failures #363
Description
I am trying (with little success) to debug an issue with intermittent DNS resolution failures on my network. Symptom is that clients report "Temporary failure in name resolution" for periods of 30-60 seconds, then start working again.
To me this smells like there is a single resolver in my pool of 20 that is failing to respond, and this heals itself when stubby moves onto the next resolver in the round-robin pool.
However, when I have tested all the upstream resolvers in the pool, they are all working, so it would seem the issue with the upstream resolver is intermittent.
Is there a level of logging that Stubby can output that will help me track down this unreliable DNS resolver?
The only logging I get from Stubby today is when ALL upstream resolvers have failed (which it logs mercilessly).