aspnetcore: Sporadic failure of HttpRequest.Body.ReadAsync() in MVC Controller / Filter

Sporadic failure of HttpRequest.Body.ReadAsync() in MVC Controller / Filter

With a POST request of content type “application/json”, in IAsyncActionFilter.OnActionExecutionAsync() and IAsyncResourceFilter.OnResourceExecutionAsync(), reading the request body asynchronously fails sporadically: Sometimes, ReadToEndAsync() (the same with a ReadAsync() in a loop) produces an empty string, sometimes the JSON string is contained twice.

I’ve seen posts with similar issues on stackoverflow and here on github, but none of the suggested actions or workarounds solves my problem. The only temporary workaround is to use OnActionExecuting() with synchronous filters and IHttpBodyControlFeature.AllowSynchronousIO = true.

To Reproduce

Startup.cs Configure():

    app.UseHttpsRedirection();
    app.UseStaticFiles();
    app.Use((context, next) =>
    {
        context.Request.EnableBuffering();
        return next();
    });
    app.UseRouting();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute(
            name: "default",
            pattern: "{controller=App}/{action=Desktop}");
    });

PayloadResourceFilterAttribute.cs:

   [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public class PayloadResourceFilterAttribute : Attribute, IAsyncResourceFilter, IOrderedFilter
    {
        [...]
        
        private ResourceExecutingContext _filterContext;
        private HttpRequest _request;
        private string _url;
       
        [...]

        public async Task OnResourceExecutionAsync(ResourceExecutingContext context, ResourceExecutionDelegate next)
        {
            [...]
            var proceed = await getJsonRequestData();
            if (!proceed) return;
            [...]
            await next();
        }

        public async Task<bool> getJsonRequestData()
        {
            if (_request.ContentType == null ||
                !_request.ContentType.StartsWith("application/json", StringComparison.InvariantCultureIgnoreCase))
            {
                return true;
            }

            if (!_request.Body.CanSeek)
            {
                _request.EnableBuffering();
            }
            _request.Body.Position = 0;

            using var reader = new StreamReader(
                    _request.Body,
                    encoding: Encoding.UTF8,
                    detectEncodingFromByteOrderMarks: false,
                    leaveOpen: true);

            // 
            // HERE, sometimes body is empty or has its value doubled:
            // (also happens with a ReadAsync() in a loop)
            // =====================================

            var body = (await reader.ReadToEndAsync()) ?? "";

            _request.Body.Position = 0;

           [...]
        }
        [...]
    }

AutoAuthController.cs:

    [PayloadResourceFilter]
    public class AutoAuthController: Controller
    {
        [...]
        /*
            AutoAuthController itself implements OnActionExecuting(), where it uses the results from 
            PayloadResourceFilter stored in HttpContext.Items.
        */
        [...]
    }

and finally, the controllers with routing endpoints derive from AutoAuthController, e.g. public class ApiController : AutoAuthController

When posting to e.g. ApiController, in nine out of ten cases everything works fine. But at some point, even when repeatedly posting to the same URL with the same JSON body, the request fails with the behavior described above.

I’m not using any other custom or third-party filters / middleware.

ON A SIDE NOTE:

While debugging, a third issue has come up: In few cases, PayloadRequestFilter.OnRequestExecutionAsync() seems not to be called before AutoAuthController.OnActionExecuting(), if at all.

Exceptions (if any)

None.

Further technical details

ASP.NET Core version 5.0.5

Output of dotnet --info

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

Runtime Environment: OS Name: Windows OS Version: 10.0.19041 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\5.0.201\

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

.NET SDKs installed: 5.0.201 [C:\Program Files\dotnet\sdk]

.NET runtimes installed: Microsoft.AspNetCore.All 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Microsoft Visual Studio Community 2019

Version 16.9.1 VisualStudio.16.Release/16.9.1+31105.61 Microsoft .NET Framework Version 4.8.04084

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