ANCM in-proc hosting scenario

[Rick-Anderson]

aspnet/AspNetCoreModule#265

see aspnet/Announcements#288

[guardrex]

Cross-ref:

• https://blogs.msdn.microsoft.com/webdev/2018/02/28/asp-net-core-2-1-0-preview1-improvements-to-iis-hosting/
• https://github.com/shirhatti/ANCM-ARMTemplate#how-do-i-try-it%EF%BB%BF
• Standup 👉 https://youtu.be/v4xxt8f639w?t=9m59s
• No sharing of app pool in-proc. See: Can multiple sites share an application pool? #7356 (comment)
• Inproc: If there is an open connection, app_offline.htm won't work until the default shoutdownTimeLimit (90 seconds) of IIS worker process aspnet/AspNetCoreModule#243

[guardrex]

Adding the blurb from the 2.1-preview2 roadmap blog post:

Version agility

Since ANCM is a global singleton, it can’t version or ship with the same agility as the rest of the ASP.NET Core. In 2.1, we’ve refactored ANCM into two pieces: the shim and the request handler. The shim will continue to be installed as a global singleton, but the request handler will ship as part of the new Microsoft.AspNetCore.Server.IIS package which can be referenced directly by your application. This will allow you to use different versions of ANCM with different app deployments.

In-process hosting

In 2.1, we’re adding a new in-process mode to ANCM for .NET Core based apps where the runtime and your app are both loaded inside the IIS worker process (w3wp.exe). This removes the performance penalty of proxying requests over the loopback adapter. Our preliminary tests show performance improvements of around ~4.4x compared to running out-of-process. Configuring your app to use to use the in-process model can be done using web.config, and will be eventually be the default for new applications targeting 2.1:

<aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" hostingModel="inprocess" />

Alternatively, you can set a project property in your project file:

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

[guardrex]

@Tratcher @jkotalik How do I describe ANCM's role now for requests coming from IIS on their way to IISHttpServer? (Step 3)

1. Requests arrive from the web to the kernel-mode HTTP.sys driver.
2. The HTTP.sys driver routes the requests to IIS on the website's configured port.
3. WHAT happens here? ... passes the request to a custom IServer implementation, IISHttpServer.
4. After IISHttpServer picks up the request, the request is pushed into the ASP.NET Core middleware pipeline.
5. The middleware pipeline handles the request and passes it on as an HttpContext instance to the app's logic.
6. The app's response is passed back to IIS, which pushes it back out to the HTTP client that initiated the request.

Does ANCM still handle the request?

[Tratcher]

That about covers it. ANCM serves two roles for in-proc:

1. it does the app initialization, loads the CLR, calls Program.Main, etc..
2. it's the native module in the IIS pipeline that surfaces requests to IISHttpServer.

[jkotalik]

For 3, the native HttpContext is converted into a managed http context, which is routed through the IISHttpServer.

ANCM handles the lifetime of the native request, which managed code pinvokes into to call certain methods, ex: ReadRequestBody, WriteResponseHeaders, etc.