Azure App Service stuck on 100% CPU usage even though all services are stopped

Question

I switched today to one app service with two deployment slots for integration and production instead of two app services running on the same App Service Plan. Now I noticed that since my last swap (which took over 7 minutes) my CPU usage is constantly on 100% which so far never happened before when I had the two app services and which does not really make sense since the application is not doing anything. Also I stopped all my App Services and the usage is still on 100%. My integration slot is not even able to start because it takes too long.

As you can see from the graph, it used to spike from time to time before, but it always went down pretty fast again as well. now it just stays up

The programm is a blazor WASM project with a asp.net core backend. It runs on a S1 plan. In that time frame where the CPU usage was so high no one was even activly using the application, which makes it even stranger.

What is happening here and how can I mitigate this?

Answer 1

Have you tried using the App Service diagnostics to see if it gives you any insights?

If you use the interactive interface mode there is specifically a CPU usage option.

Azure portal > Your resource group > Your app service > Diagnose and solve problems.

Also there is a bunch of native logging that you can turn on. Have Application Insights plugged in also wouldn't hurt.