Aspnetcore: ASP.NET Core 2.2 memory leak

[kameleon71]

Hello all,
I found memory leak when I sent files to API using IFormFile interface.
With version 2.1 everything is ok.

Simple example:
Content-type: multipart/form-data

controller

[ApiController]
public class FormController : ControllerBase
{
    [HttpPost]
    [Route("[controller]/Insert")]
    public async Task<IActionResult> Insert([FromForm] Form form)
    {
        return Ok();
    }
}

viewmodel

public class Form
{
    public string Name { get; set; }
    public IFormFile File { get; set; }
    public ICollection<DynamicInput> Inputs { get;set; }
}

public class DynamicInput
{
    public string Name { get; set; }
    public IFormFile File { get; set; }
}

process dotnet.exe

[davidfowl]

@kameleon71 Can you provide a full repro? (Client included).

[kameleon71]

Here you are: https://github.com/kameleon71/asp.net.core.2.2.memory.leak
This example is based on template asp.net.core web app in VS2017 (angular client)
Just run, click fetch data and watch memory usage ;)

[travisjs]

@davidfowl any status on this; we have this issue too...

[travisjs]

@davidfowl

This seams to be caused by the following method being called when an array of IFormFiles has to be parsed by the ModelBinder. It does a loop with an upper range of int.MaxValue

https://github.com/aspnet/AspNetCore/blob/1aa50faa290ecda304507981cd01ed92651d5e34/src/Mvc/src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Binders/CollectionModelBinder.cs#L310-L324

[davidfowl]

cc @pranavkm

[pranavkm]

@dougbu is this the same class of issue as https://github.com/aspnet/AspNetCore/issues/7052?

[Plasma]

We upgraded to .NET Core 2.2 and memory climbed to 100% over a few days easily. I'm not sure of the cause yet but have taken a few memory dumps but unable to analyze right now, will hopefully understand more soon.

[dougbu]

This issue is a duplicate of #4802. The #6793 fix will correct both issues, in 3.0 Preview 3 we hope.

(@pranavkm #7052 relates to binders that succeed unconditionally (and repeatedly) in the same request. The FormFileModelBinder isn't in that category.)

[danyae]

I have also experienced this problem and for those who doesn't want to revert back to .Net Core 2.1 I suggest using Non-Sequential Indices like described in this article: https://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx/.

In my views I create a string guid index and then use it to bind a model to a list:

@{var fileGuid = Guid.NewGuid().ToString();}
<input type="hidden" name="DocumentsForm.TypedFileList.Index" value="@fileGuid" />
<input type="file" name="DocumentsForm.TypedFileList[@fileGuid].File" class="inputfile"  />