In the current code, if Spectrum cannot contact Device Manager for 5 minutes, Spectrum will automatically disable the event polling service.
Presently, we do not have a mechanism to let users know when Spectrum is unable to contact Device Manager other than by seeing the following error message in the tomcat log file.
(GlobalPool => NPCEventManagerWebserviceURLPoller) (NetqosEventLog) - (ERROR) - Unable to contact Event Manager - stopping all polling.
Development is working on generating an event on the VNM model which will notify users of this change. They are also looking into automatically re-enabling this service once contact has been re-established. This will be included in a future release of Spectrum.