ANCM: IISExpress and switching hostingModel

[shirhatti]

From @jhkimnew on March 1, 2018 1:19

We need to update DOC to inform this limiation regarding IISExpress.

Unlike full IIS, IISExpress should restart after switching hostingModel from inprocess to outofprocess because it does not use WAS service.

Copied from original issue: aspnet/IISIntegration#621

[guardrex]

@jhkimnew @shirhatti Should we say a bit more ... should it say how the restart may negatively impact an app/hosting (examples)?

Also, confirm: Should this bit describe setting hostingModel? (applicationHost.config? ... I'm looking at some resources now on how IIS Express is configured)

Related: Allow IISExpress deployer to deploy either inprocess or outofprocess based on a deployment parameter (aspnet/Hosting #1260)

[jhkimnew]

@pan-wang Can you add more detailed information about why IISExpress needs to be restarted manually when hostingModel is changed?

[guardrex]

Yes, I need more background info and context to document this.

cc/ @jkotalik You had a PR (aspnet/Hosting #1261) on at least part of this. Can you help?

RE: Where?

One of the problems to address is where we should document this. We don't have much to say about IIS Express configuration in this doc set. It's not really a Host and deploy thing. It doesn't fit with the app-centered Hosting or Error handling topics. Since IIS Express is used for local debugging, it feels more like a Test and Debug area thing, but we don't document IIS Express there. As things stand, I don't know where we put this content.

RE: Content

I understand that IIS Express starts and the process continues to run after it's started (it continues to run even after the debugger is stopped in VS). If the hostingModel is changed either way (inprocess to out- or out- to in-), I think I understand that you're saying that IIS Express must be restarted manually to pickup the change. Since stopping the debugger in VS doesn't stop the IIS Express process, what do we need to say about how to manually restart IIS Express if the hostingModel is changed?

RE: Configuration of hostingModel

Are we talking applicationhost.config kept in %userprofile%\documents\IISExpress\config? "hostingModel" isn't in the file (on my machine anyway). How is the hostingModel configured?

[guardrex]

@vaidy4github Is this issue covered by any of your IIS Express docs?

TL;DR: Unlike full IIS, IISExpress should be restarted after switching hostingModel from in-process to out-of-process because it does not use the WAS service.

[shirhatti]

Also, confirm: Should this bit describe setting hostingModel? (applicationHost.config? ... I'm looking at some resources now on how IIS Express is configured)

The eventual goal is to add a drop-down to the project property page that allows you to pick between the different hosting model.
It can also be achieved by adding this property to your csproj.

  <PropertyGroup>
    <AspNetCoreModuleHostingModel>inprocess</AspNetCoreModuleHostingModel>
  </PropertyGroup>

Or overridden via a launch profile in launchSettings.json

I'd suggest tracking this as part of the uber issue you've created for ANCM in-proc. We can setup a meeting where I demo in-proc when you're ready to actually to tackle this doc.

[guardrex]

@shirhatti I'm glad u mentioned that. It clears up my Where? question. But one thing tho ...

I didn't know we would have a separate topic for inproc. I thought we'd be rolling it into the current ANCM topic in Servers (as perhaps just an overview section) and into the current ANCM reference topic in Host and deploy: Host on Windows with the details.

Is there enough content to have a standalone topic just for inproc?

Your configuration notes are perfect, but what do we need to say about how to restart IIS after the hostingModel setting is changed? Today, it looks like you have to manually kill the IIS Express process (guessing).

[jkotalik]

The inprocess mode is large enough to delicate a new document section for it. Though it bootstraps through ANCM, in managed code it is a completely different hosting model (uses a custom IServer).

Once the hostingModel setting has been changed in the web.config file, ANCM will notice a configuration change and recycle the worker process for IIS. For IISExpress, instead of recycling will trigger a graceful shutdown and close the current iisexpress process.

[guardrex]

Once the hostingModel setting has been changed in the web.config file, ANCM will notice a configuration change and recycle the worker process for IIS. For IISExpress, instead of recycling will trigger a graceful shutdown and close the current iisexpress process.

Perfect ... thanks. That's exactly what I needed to know.

I think I have everything (that's known to date) to document it. Please ping me here with any new developments. I've been so busy with doc issues that I'm having a hard time keeping up with engineering repo issues.

Cross-ref: https://blogs.msdn.microsoft.com/webdev/2018/02/28/asp-net-core-2-1-0-preview1-improvements-to-iis-hosting/