Web apps HTTP Error 503 and WAS event 5189 on Windows 10

Cause of web applications HTTP error 503 and WAS event 5189

This error can occur because the Windows Activation Service (WAS) creates a temporary configuration file for each IIS application pool in the folder below during a standard operation.

C: inetpub temp appPools

During an initial upgrade phase, Windows Update scans existing folders and files (outside of the Windows folder) and saves their paths to restore after the upgrade. However, since the configuration files are temporary, they are deleted when WAS is stopped.

In the next phase of Windows Update, these previously scanned files and folders are copied to a temporary upgrade location. After Windows upgrades, Windows Update creates a symbolic link to each folder that has been copied to a temporary upgrade location before attempting to restore these files and folders to their original locations.

However, since these temporary configuration files no longer exist, Windows Update does not remove symbolic links.

When WAS attempts to start as an IIS worker process, it does not create a temporary folder to write the configuration because of symbolic links. Therefore, Http.Sys returns an HTTP 503 error.

How to resolve HTTP error 503 for web applications and WAS event 5189

To resolve this problem, Microsoft recommends that you manually delete symbolic links (symbolic links can be deleted in the same way as normal files) created by Windows Update. To do so, follow these steps.

Open the command prompt in elevated mode, copy and paste the command below and press Enter:

net stop WAS /y
rmdir /s /q C:inetpubtempappPools
net start W3SVC

I hope this message will help you!