We've confirmed that all systems are back to normal with no customer impact as of 05/16, 09:55 UTC. Our logs show the incident started on 05/16, 00:55 UTC and that during the ~9 hours that it took to resolve the issue some customers who have configured alerts prior to 05/16, 00:55 UTC might not have received alert fired or alert resolved events during the impacted window.
Root Cause: The failure was due to configuration issues with one of our dependent service.
Incident Timeline: 9 Hours - 05/16, 00:55 UTC through 05/16, 09:55 UTC
We understand that customers rely on Application Insights as a critical service and apologize for any impact this incident caused.
Update: Thursday, 16 May 2019 08:59 UTC
We continue to investigate issues within Application Insights. Some customers who configured alerts prior to the start time will not receive alert fired or alert resolved events during the impact window. The problem began at 05/15 ~12:55 UTC.