Microsoft reveals that unseen code errors in its Azure DNS service caused the April 1 outage.
Microsoft has revealed the root cause of the recent outage affecting Azure, which lasted about an hour and was due to a surge in Domain Name System (DNS) requests coupled with a code defect. Users were reporting that Azure Portal, Azure Services, Dynamics 365, and Xbox Live were inaccessible during the worldwide outage between 21:21 UTC and 22:00 UTC on 1 Apr 2021. Microsoft said in its root cause analysis report that the majority of services recovered by 22:30 UTC. While Microsoft quickly confirmed the outage was related to its DNS capabilities, the company’s final root cause analysis published April 4 sheds a bit more light on the cause being a previously unseen code defect in its DNS service that was triggered by excessive DNS client retries.
