Blazor Support Large File Uploads

[christophwille]

I have a working Blazor Web Assembly app that uploads files to Azure Storage (server provides SAS token urls, client upload to that destination). This works a-ok for "small" files the size of a couple 100MBs. However, I now have a 6.8GB file that doesn't - I am using bog standard code along the lines of the documentation:

Azure.Response<BlobContentInfo> azresponse = await blobClient.UploadAsync(fileStream, new BlobUploadOptions()
{
  ProgressHandler = new Progress<long>((progress) =>
  {
     vm.ProgressBarPercentage = (int)(100.0 * progress / vm.InputFileSize);
     this.StateHasChanged();
  })
});

For this large file, it returns immediately and creates a zero byte file on Azure Storage. I then tried this:

 var x = new byte[200];
 int res = await fileStream.ReadAsync(x, 0, 100);

Surprisingly, res is 0 so I see why the storage library would create a 0 byte file... but I don't get why Blazor behaves that way. (Note: I didn't test to see at what file size this behavior kicks in). I also didn't see anything that would indicate any sort of error. The stream simply isn't returning data.

[javiercn]

@christophwille thanks for contacting us.

Is the stream returning a 0 for the read coming from the InputFile component?

[christophwille]

IBrowserFile.Size is telling me the on-disk file size as expected. IBrowserFile.OpenReadStream(8 * 1024 * 1024* 1024) (my current default max limit is 8GB) is giving me a Stream but... then trying to read from it doesn't return anything (no need to upload to Azure, my ReadAsync sample from above is fully sufficient to exhibit the problem - no bytes read)

[javiercn]

@christophwille thanks for the additional details.

@TanayParikh since you are fiddling with this area, can you give this a try? (Both with the improved implementation and with the old implementation in 5.0)

Thanks for contacting us.

We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[TanayParikh]

@TanayParikh since you are fiddling with this area, can you give this a try? (Both with the improved implementation and with the old implementation in 5.0)

Looks like we have a hard limit of Int32.MaxValue = 2147483647 bytes on the file size we can currently upload. This applies for Blazor WASM and Blazor Server. Compiling benchmarks of old vs new implementation and will update accordingly.

[christophwille]

Is there a chance to lift this limit in either a point relase for v5 or v6 (I am selfish, WASM-only would be fine)?

Edit: or make it configurable ("I know what I am doing"). But failing silently with 0 bytes is a very strange behavior.

[christophwille]

Will #33491 lift the limit mentioned in this issue or is this then still another different matter? (I'd be fine moving to Blazor 6 in this specific case, but if it is not gonna get lifted I need to switch to JavaScript)

[TanayParikh]

Will #33491 lift the limit mentioned in this issue or is this then still another different matter?

No unfortunately the limit remains after #33491. I'm investigating if there's a way for us to add in support for files > 2GB, will update here accordingly.

[TanayParikh]

I've put up a proof of concept on what it'd take to implement large file support: #33900