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Modifying the application web.config file in an NLB cluster

I would like to know what will affect the change of the web.config file while the ASP.NET application is running.

Here's my exact scenario. I have two hosts running the same application on IIS6. Both hosts have the same machine.config files, which means they use the same machine keys.

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[HOST A]----[NLB]---[HOST B]
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[SQL server for ASP.NET sessions]

The application must be available to users every day from 7:00 to 18:00. At 19:00, hosts A and B reboot and we can do some application updates on both hosts. But sometimes we would like to be able to make updates while the application is running. Updates often consist of adding some values ​​to the web.config which, as far as I know, force the application to restart.

The application relies heavily on sessions, but they are stored on the SQL server, and only the cache data is kept in the server's memory, and it doesn't matter if that data is lost. But losing user sessions is completely unacceptable. My question is, what will users experience if we change the web.config file on one of the hosts in the web farm if the server is currently executing a user request? And what happens if a new request comes in while the application is restarted?

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Well, you already gave the answer yourself. Sessions are usually interrupted during a restart, but you are using SQL Server to save them so they will not be lost.



However, new visitors will receive an error page on restart. But they won't start a new session, so the visitor can just keep F5'ing until the app is running.

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