This error message is being generated by the
ShutdownMonitor which is the manager that listens for Web App shutdown commands. When the webapp receives an instruction for shutting down, this monitor fires the
Stop() method, which writes this error message.
Essentially, what's happening is that the Azure WebApp Service is attempting to do something that is about to cause the web application to recycle. As a result, this stop method is going to interrupt any indexing that is going on.
An Azure Webapp service can recycle for any number of reasons, some common ones are as follows:
- WebApp Service Host is being rebooted by Microsoft for Updates
- Enough Application Errors bubbled to the top of the WebApp stack to cause the AppService to recycle (this is the most common reason for WebApp reboots)
- A deployment occurred which will also recycle the AppService.
The indexing process can not ignore this request, because there are clean up actions that have to quickly be taken care of before the WebApp Service is rebooted. So the process ends all indexes, to allow for a safe WebApp Service reboot.