Azure App Service set to manually scale 2 instances is running 4 instances. Why?

Question

I have an app service which is running a razor pages app. I conducted a load test today. I scaled the app service manually to 2 instances.

I ran a 5 minute test and watched the application insights dashboard. I saw 2 instances. At the end the test, I saw 4 instances.

Am I being charged for all 4 instances?

For now, I scaled back down to 1 instance. But I cannot continue my load tests because I have 4 instances running and I don't want 4 instances running.

How do I get rid of these instances?

Thank you for your consideration.

An hour later, I still have 2 instances running even though I scaled down to 1 instance more than an hour ago.

Answer 1

RobertGalante-0992, Firstly, please accept my delayed response on this.

From your last screenshot, it looks like you’re pointing to Live Stream ‘4’ servers may not be related to Azure App Service and maybe Azure Media Service.

--Just to highlight, there are two main processes for an Azure web app. There is the w3wp.exe process, which runs the website itself.
The second main process is the w3wp.exe scm process, which runs KUDU.

--You can observe your site processes by navigating to (replace yoursitename with your web app name) https://yoursitename.scm.azurewebsites.net/ProcessExplorer/

--Furthermore, if you have multiple Apps in an App Service Plan (ASP). All the apps in the same ASP share the same compute resources.

In a nutshell, the ASP is the scale unit of the App Service Apps. If the plan is configured to run 4 VM instances, then all apps in the plan run on all 4 instances.
--If the plan is configured for autoscaling, then all apps in the plan are scaled out together based on the autoscale settings. You pay for the ASP, not for # the Apps.

--VM name(starts with RD), you may check this discussion thread for more info.

--You may also review the scaling operations via "Diagnose and solve problems", by navigating to Azure Portal and select the WebApp in question.

Kindly let us know, if the issue still persist, I'll follow-up with you privately further to provide quick and specialized assistance.

Answer 2

I submitted a request to MS support for clarification on how MS charges for an App Service plan using S1 machines.

They told me in their response that the S1 machines require more than one server per instance. That is why I see twice the number of servers in the Application Insights.

Also they told me that I will not be charged for the additional servers.

It's not very intuitive to have Application Insights reporting the number of server the way it does. But at least I know now.

I have another App Service Plan with Linux B1 machines. These do not report to Application Insights with a different number of servers. When I mentioned this to them, they replied that the B1 machine only require 1 server per instance.

Thanks for your help through this experience. I think we can close this issue.