IISPlatformHandler's Debug request reaches the users application

[NTaylorMullen]

If you have the following in your startup application:

app.Run(async (context) =>
{
    await context.Response.WriteAsync("Hello World!");
});

You'll see the middleware be invoked twice.

[Eilon]

Hmm why is this a tooling bug?

[NTaylorMullen]

Tooling is the one performing two requests 😄.

1. The normal page request when hitting F5
2. An extra DEBUG request to kick start DNX and attach.

[Eilon]

I don't think tooling will stop sending the DEBUG request - it has to do that. Is the bug that the request makes it past some DNX/Hosting thing?

[NTaylorMullen]

From talks with @BillHiebert it sounded like tooling could write a nativish module to eat the request.

[Eilon]

Ah ok...

[sayedihashimi]

Is there any action needed here? I think @BillHiebert may have already fixed this but not totally sure.

[BillHiebert]

I think the fix would need to occur in middleware. I don't see how tooling can fix this as we need to send a request to get the httpPlatformHandler to start dnx.exe.

[Eilon]

@davidfowl @Tratcher any thoughts on this? Can/should we block the DEBUG request from VS at some early layer? I think this might be what's happening here: aspnet/Mvc#3585

[Tratcher]

This would be easy for the UseIISPlatformHandler middleware to eat.

[NTaylorMullen]

@Tratcher Is it possible to do it earlier? This problem occurs with any server as long as you start it with debugging.

[Tratcher]

It's possible, but I don't recommend it. This is specific to IIS/Express and VS. UseIISPlatformHandler is the second item in our templates after the debugging tools: https://github.com/aspnet/Templates/blob/dev/src/BaseTemplates/StarterWeb/Startup.cs#L49

[NTaylorMullen]

Still dependent on where you put it though :/

[Eilon]

UseIISPlatformHandler has to be super early to work at all.