ProfessorRight. "no data" should be on par with critical, error and warning so the threshold can be overridden properly if needed for specific devices/groups. It is very hard to know without digging into each DP definition when "no data" will even alert (no indication in the tuning page) and it is definitely unclear when you can unambiguously check (most times at least, the "no data" status applies to a datapoint that otherwise has no competing alert threshold). I also run into embarrassing situations where data acquisition has silently failed due to collection faults -- LM has been adding more troubleshooters to help there, which is appreciated. Still, I just ran into an issue with the "new/improved" Cisco WLC datasource group where APs that are disconnected don't even have a "no data" DP anymore, so you cannot know this happened. In fact, that DS now removes dead instances immediately. Realized this weekend as we moved from Cisco WLC to Meraki that not a single alert generated from WLC APs as they were disconnected -- they just vanished from existence. Technically true, but should be in alarm until confirmed intentional. The only way to fix this now is to edit the DS, which I loathe doing as it (for now) severs my tie to the original and creates a risk that an update will break changes. I am not a fan of cloning as it also severs the tie to the original and makes updates painful.
