Phantom response being issued by custom middleware

Describe the bug

My custom timeout middleware is responding with data from another, already “dead”, response.

To Reproduce

This custom Middleware:

public class TimeoutMiddleware
{
    private readonly RequestDelegate _next;

    public TimeoutMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext httpContext)
    {
        using (var timeoutTS = CancellationTokenSource.CreateLinkedTokenSource(httpContext.RequestAborted))
        {
            var delayTask = Task.Delay(500);

            var res = await Task.WhenAny(delayTask, _next(httpContext));
            if (res == delayTask)
            {
                timeoutTS.Cancel();
                httpContext.Response.StatusCode = 408;
            }
        }
    }
}

And this controller

[HttpGet]
public async Task<string> Get(string timeout)
{
    var result = DateTime.Now.ToString("mm:ss.fff");
    if (timeout != null)
    {
        await Task.Delay(2000);
    }
    var rng = new Random();
    result = result + " - " + DateTime.Now.ToString("mm:ss.fff");
    return result;
}

And just use fiddler to spam a dozen requests and you will see that the first ones will return 408 (as expected) but soon you will start to see a bunch of 200s. When you inspect the time on the body, you will see that the time reported is far BEHIND the request start time

Exceptions (if any)

“Response has already started” but that’s not important

Further technical details

• ASP.NET Core version: .Net 5 and 3.1
• Include the output of dotnet --info:

.NET SDK (reflecting any global.json): Version: 5.0.201 Commit: a09bd5c86c

Runtime Environment: OS Name: Mac OS X OS Version: 11.0 OS Platform: Darwin RID: osx.11.0-x64 Base Path: /usr/local/share/dotnet/sdk/5.0.201/

Host (useful for support): Version: 5.0.4 Commit: f27d337295

.NET SDKs installed: 2.1.202 [/usr/local/share/dotnet/sdk] 2.1.802 [/usr/local/share/dotnet/sdk] 2.2.207 [/usr/local/share/dotnet/sdk] 3.0.100 [/usr/local/share/dotnet/sdk] 3.1.100-preview2-014569 [/usr/local/share/dotnet/sdk] 3.1.100-preview3-014645 [/usr/local/share/dotnet/sdk] 3.1.100 [/usr/local/share/dotnet/sdk] 3.1.101 [/usr/local/share/dotnet/sdk] 3.1.102 [/usr/local/share/dotnet/sdk] 3.1.200 [/usr/local/share/dotnet/sdk] 3.1.202 [/usr/local/share/dotnet/sdk] 3.1.300 [/usr/local/share/dotnet/sdk] 3.1.301 [/usr/local/share/dotnet/sdk] 3.1.302 [/usr/local/share/dotnet/sdk] 3.1.401 [/usr/local/share/dotnet/sdk] 3.1.402 [/usr/local/share/dotnet/sdk] 3.1.403 [/usr/local/share/dotnet/sdk] 3.1.404 [/usr/local/share/dotnet/sdk] 3.1.405 [/usr/local/share/dotnet/sdk] 3.1.406 [/usr/local/share/dotnet/sdk] 3.1.407 [/usr/local/share/dotnet/sdk] 5.0.100 [/usr/local/share/dotnet/sdk] 5.0.101 [/usr/local/share/dotnet/sdk] 5.0.102 [/usr/local/share/dotnet/sdk] 5.0.103 [/usr/local/share/dotnet/sdk] 5.0.201 [/usr/local/share/dotnet/sdk]

.NET runtimes installed: Microsoft.AspNetCore.All 2.1.13 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.8 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.1.13 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.8 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.0-preview2.19528.8 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.0-preview3.19555.2 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.1 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.2 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.4 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.6 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.7 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.8 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.9 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.10 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.11 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.12 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.13 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.1 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.2 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.4 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.NETCore.App 2.0.9 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.13 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.14 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.15 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.16 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.17 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.18 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.19 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.20 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.21 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.22 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.23 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.8 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.0-preview2.19525.6 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.0-preview3.19553.2 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.1 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.2 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.4 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.5 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.6 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.7 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.8 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.9 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.10 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.11 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.12 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.13 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.1 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.2 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.4 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

• The IDE (VS / VS Code/ VS4Mac) you’re running on, and its version Visual Studio for Mac, version 8.9.2 (build 0) (yeah the build number is ZERO, really weird)

[davidfowl]

If that were a concern then you could pool them 😄.

[davidfowl]

BTW the above code has a mini-timer leak, you can see the bad and good pattern here https://github.com/davidfowl/AspNetCoreDiagnosticScenarios/blob/a87d6b804d8924e8487f3bf79f37fe9973049649/Scenarios/Infrastructure/TaskExtensions.cs#L48-L89