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  • Peter Laurie 39 posts 112 karma points
    Jun 03, 2022 @ 04:15
    Peter Laurie

    Umbraco 9 - ASP.NET Core does not support multiple apps in same app pool

    We are running Umbraco 9 in a Load balancing set up. One backend server, and two front end servers. We have had the following error on a few occasions:

    HTTP Error 500.35 ASP.NET Core does not support multiple apps in the same app pool

    We use Task Scheduler to copy changes to front end servers (excluding ~/umbraco/Data/TEMP), for example when we update the website or need to copy a new image in the media folder to the front end servers.

    The second instance of running task scheduler at the same time as when the site is up, may be the route of this issue. We are determining this, as this is the core of my question here.

    Have others experienced this on a Load Balanced set up on Umbraco 9 (we did not get this on Umbraco 8) and how was it solved please?

    Have other forum members good suggestions for file replication, like media folder changes, to have changes copied to the front end servers without interfering with the app, pool running the website on the front end server?

    What are any recommendations of using InProcess or OutOfProcess web configuration on load balanced Umbraco 9 websites running in IIS?

    Thank you in advance,

    Kind regards,


  • rok 3 posts 73 karma points
    1 week ago

    Hey, did you maybe solve this issue? Are you maybe willing explain some steps?

  • Peter Laurie 39 posts 112 karma points
    7 days ago
    Peter Laurie

    Hi, Yes, sorry, we did find out what was wrong.

    .NET CORE does not support multiple apps in the same application pool on IIS, whereas using .NET Framework 4.6 - when we were on Umbraco 8, IIS was ok with that.

    We used to run amp pages in the past, which we do not now. When someone accessed the website with a prefix amp, the site would serve stripped down templates.

    On looking at the IIS application pool, we found that the amp application pool was still pointing at the main Umbraco site location which we had subsequently upgraded to Umbraco 9.

    We managed to replicate the issue on test, so when we deleted the amp pool the issue went away.

    Please excuse me not putting up the solution, in the hectic work with Umbraco 9 going on, this was overlooked.

    Kind regards,


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