Kestrel MaxRequestBodySize uploading file over the limit

Question

I did encounter a wierd problem with kestrel. I am not able to upload the multiple files which exceed the kestrel's MaxRequestBodySize.

The expected behaviour is to throw the BadHttpRequestException when I am trying to reader this.Request.Form.Files.GetFiles(). I do expect to recieve request to controller action only once.

What is happening is that the upload action is hit a few time and browser with message "conection lost". I did not find a patter on how mamy times the action is called.

Controller action:

[HttpPost("upload")]
public IActionResult Upload()
{
    try
    {
        var files = this.Request.Form.Files.GetFiles("files");
        files.Select(async file => await this.SaveFile(file))
        return this.RedirectToAction(nameof(VueController.FilesList),"Vue");
    }
    catch (BadHttpRequestException exp)
    {
        return new string[]
        {
            exp.Message
        };
    }
}

view:

<form method="post"
          enctype="multipart/form-data"
          action="/api/v1/files/upload"
          novalidate="novalidate">
      <input type="file"
             name="files"
             multiple="multiple"
             required="required"
             accept=""
             capture="capture" />
    </form>

asp.net core logs:

info: Microsoft.AspNetCore.Server.Kestrel[17] Connection id "0HLDB9K94VV9M" bad request data: "Request body too large." Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException: Request body too large. at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Frame.ThrowRequestRejected(RequestRejectionReason reason) at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.MessageBody.ForContentLength.OnReadStart() at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.MessageBody.TryInit() at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.MessageBody.d__24.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Frame`1.d__2.MoveNext() info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2] Request finished in 7618.6319ms 413

Edited I am aware that I can disabled the limit but it is not possible in this case.

Answer 1

You must configure two things:

In your Program.cs

public static IWebHost BuildWebhost(string[] args) => 
   WebHost.CreateDefaultBuilder(args)
      .UseStartup<Startup>()
      .UseKestrel(options => {
           options.Limits.MaxRequestBodySize = null; // or a given limit
      })
     .Build();

In your Startup.cs in the ConfigureService method

services.Configure<FormOptions>(options => options.MultipartBodyLengthLimit = long.MaxValue); // or other given limit

Also change your controller endpoint to use [FromForm]

public IActionResult Upload([FromForm] IEnumerable<IFormFile> files)... // name must be same as name attribute of your multipart form

Now ASP.NET Core will do the work and inject the files from the form as sequence.

Edit:

I created an example that can be cloned from github:

git clone https://github.com/alsami/example-fileupload-aspnet-core.git
cd example-fileupload-aspnet-core
dotnet restore
dotnet run --project src/file-upload-api/file-upload-api.csproj

Then navigate to http://localhost:5000/index.html and try uploading huge files.