If deploy an ASP.NET Core as a web app to Azure, what is used for hosting?

Question

ASP.NET Core out of the box supports hosting in IIS and self-hosting scenarios using the Kestrel and WebListener HTTP servers. Accordingly to web.config / project.json looks like IIS is used, but if so it is not clear for my "why" so, as now IIS is acting just as a reverse proxy and the application itself runs as a separate process using the Kestrel HTTP server.

So the main question is "what" and "why" is used by default, if deploy to Azure?

Answer 1

Yes, when you publish to Azure Web Services, IIS is used to host your application. As you said, it acts as a reverse proxy to your application, which is running Kestrel HTTP server. But IIS does more than that - it also manages the application process through application pool, which includes or may include:

• restarting the app when web.config changes
• starting the app on the first HTTP request
• running the app as a specified user
• recycling the app pool (and effectively restarting the app) on certain conditions
• starting multiple app processes
• handle webdeploy (this is what happens when you hit "Publish" in Visual Studio