We've confirmed that all systems are back to normal with no customer impact as of 01/22, 19:00 UTC. Our logs show the incident started on 01/22, 17:30 UTC and that during the 1 hour 30 min that it took to resolve the issue some customers might have experienced Data access and Latency issues in portal(Azure and OMS) for East US region.
Root Cause: The failure was due to an issue with dependent service.
Incident Timeline: 1 Hour & 30 minutes - 01/22, 17:30 UTC through 01/22, 19:00 UTC
We understand that customers rely on Azure Log Analytics as a critical service and apologize for any impact this incident caused.
Update: Tuesday, 22 January 2019 18:26 UTC
Some Log Analytics customers may experience Data access and Latency issues in portal(Azure and OMS) for East US region. we applied the mitigation and estimate this issue will be mitigated in 1 hour.