Final Update: Thursday, 12 December 2019 13:54 UTC
We've confirmed that all systems are back to normal with no customer impact as of 12/12, 13:30 UTC. Our logs show the incident started on 12/12, 11:00 UTC and that during the 2 Hours & 30 minutes that it took to resolve the issue some of customers experienced delay in receiving all alert types.
Root Cause: The failure was due to an issue with one of our dependent service.
Incident Timeline: 2 Hours & 30 minutes - 12/12, 11:00 UTC through 12/12, 13:30 UTC.
We understand that customers rely on Azure Monitor as a critical service and apologize for any impact this incident caused.