Unable to disable buffering once enabled

[TaoziZ03]

Summary

Hi, I am migrating a web to net core. The line 68 enable response buffering if HttpApplication events are needed. This disables our cache policy in later code.

systemweb-adapters/src/Microsoft.AspNetCore.SystemWebAdapters.CoreServices/SystemWebAdaptersExtensions.cs

Lines 59 to 81 in c2607be

	internal static void UseSystemWebAdapterFeatures(this IApplicationBuilder app)
	{
	if (app.HasBeenAdded())
	{
	return;
	}
	if (app.AreHttpApplicationEventsRequired())
	{
	app.UseMiddleware<HttpApplicationMiddleware>();
	}
	app.UseMiddleware<PreBufferRequestStreamMiddleware>();
	app.UseMiddleware<BufferResponseStreamMiddleware>();
	app.UseMiddleware<SetDefaultResponseHeadersMiddleware>();
	app.UseMiddleware<SingleThreadedRequestMiddleware>();
	app.UseMiddleware<CurrentPrincipalMiddleware>();
	if (app.AreHttpApplicationEventsRequired())
	{
	app.UseHttpApplicationEvent(ApplicationEvent.BeginRequest);
	}
	}

Motivation and goals

Allow user code to manage response buffering feature.

Risks / unknowns

Can anyone provide some insights for this design?

Repro

builder.Services.AddSystemWebAdapters()
    .AddWrappedAspNetCoreSession()
    .AddHttpApplication<MyApp>(options =>
    {
        options.RegisterModule<MyModule>("Module1");
        options.RegisterModule<MyModule>("Module2");
        options.RegisterModule<MyModule>("Module3");
.......
    });

var app = builder.Build();

// Since HttpApplication events are needed, here will add `HttpApplicationMiddleware`.
app.UseSystemWebAdapters();

app.Use((context, next) =>
{
    // This will not success because `HttpApplicationMiddleware` will enable buffering.
    if(!ShouldBufferReponse(context.Request.Path))
        context.Features.Get<IHttpResponseBodyFeature>().DisableBuffering();
    return next();
});

Here is where updated the response buffering.

systemweb-adapters/src/Microsoft.AspNetCore.SystemWebAdapters.CoreServices/HttpApplication/HttpApplicationMiddleware.cs

Line 18 in c2607be

context.Features.GetRequired<IHttpResponseBufferingFeature>().EnableBuffering(BufferResponseStreamAttribute.DefaultMemoryThreshold, default);

[twsouthwick]

Can you share a repro of what you're trying to achieve?

[TaoziZ03]

Updated

[twsouthwick]

Would adding an API like the following help here?

public class SystemWebAdapterOptions
{
+  public Func<HttpContext, ValueTask<bool>> IsBufferingEnabled { get; set; }
}

which would default to true to maintain current behavior, but allow you to override if buffering should be enabled?

[twsouthwick]

Actually, it appears that the following just doesn't work right:

ctx.Features.GetRequired<IHttpResponseBodyFeature>().DisableBuffering();

With that fixed, does your scenario become unblocked?

[TaoziZ03]

Left a comment in the PR. Let's discuss the details there.