We've confirmed that all systems are back to normal with no customer impact as of 8/28, 21:30 UTC. Our logs show the incident started on 8/28, 17:30 UTC and that during the 4 hours that it took to resolve the issue, customers in the West US Region could have experience delayed or lost Diagnostic Logs. Customers using App Services Logs in Public Preview could have also experienced missed or delayed logs in all US and Canada Regions.
Root Cause: The failure was due to a backend dependency.
Incident Timeline: 4 Hours - 8/28, 17:30 UTC through 8/28, 21:30 UTC
We understand that customers rely on Azure Monitor as a critical service and apologize for any impact this incident caused.