I have more instances than what's showing up in the Process Explorer or Advanced Application Restart

Question

Recently there was an issue where a specific instance had reached 100% CPU consumption. When I went to the Advanced Application restart tool in the Azure portal, the instance wasn't showing up there. The same thing happened with the process explorer and the kudu site. Why is this happening?

Answer 1

The behavior you are seeing is to be expected. When an instance reaches 100% CPU consumption then it does not respond to the Advanced Application restart tool or any of the other tools such as the Kudu site or the Process Explorer.

In these situations, I would recommend configuring proactive CPU monitoring for your app. More information can be found here: Mitigate your CPU problems before they happen

If the behavior is only happening on a single instance, then another option is to enable Health Check for your application: https://azure.github.io/AppService/2020/05/15/Robust-Apps-for-the-cloud.html#set-your-health-check-path
This document shares information on health check, as well as other best practices for app performance on Azure.