This humble author was recently finishing up a couple of articles and scripts before calling it a day and heading home. Then, all of a sudden, an Application Gateway started presenting 502 error pages. Looking at the metrics in the Application Gateway, we noticed no data during the time reported by the customer.
After looking at the Application Gateway, we realized that the instance count was configured as one and after a call with Microsoft support, we were informed that there was maintenance at that time that caused the outage in the Application Gateway -- and the 502 errors.
Long story short, to avoid an outage make sure that you have at least two instances in any production environment.
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