Fix: IIS error: serverruntime@appconcurrentrequestlimit setting is being exceeded

Summary: Fix the IIS error serverruntime@appconcurrentrequestlimit setting is being exceeded
Date: 23 September 2022
Refactor: 15 December 2024: Checked formatting and added some context.

This error happens on IIS when a IIS server is overloaded. By default, the app pool in which the sites live have limited concurrent requets configured. You need to change three settings as shown below. Don't forget to reboot the server afterwards. This was done and tested successful on a Windows Server 2016 with IIS 10.0

Open IIS manager:

• IIS Manager → <app pool you need to change> → advanced setting → queue length
  • Default: 1000
  • New setting: 10000

Open an administrative command prompt:

• Enter cd %windir%\System32\inetsrv\
• Enter appcmd.exe set config /section:system.webserver/serverRuntime /appConcurrentRequestLimit:15000

This adds the following line to C:\Windows\System32\inetsrv\config\applicationHost.config:

• <serverRuntime appConcurrentRequestLimit="15000" />
• Default is 5000

• Open notepad als admin
  • Open file C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config
    • Note that the framework version can change
  • Replace <processModel autoConfig="true"/>
  • With <processModel enable="true" requestQueueLimit="15000" />

Reboot the server.