HubConnectionHandler Crash When Sending Large Amounts of Data

[Jon-Murray]

Hi Guys,

I have been testing and have found the following crash whenever a "large" (2MB in my test) amount of data is sent from the server -> client. The crash occurs in the following code within HubConnectionHandler.cs:

            finally
            {
                // The buffer was sliced up to where it was consumed, so we can just advance to the start.
                // We mark examined as buffer.End so that if we didn't receive a full frame, we'll wait for more data
                // before yielding the read again.
                input.AdvanceTo(buffer.Start, buffer.End);
            }

I've modified it slightly, but here is my console output for an example crash:

Buffer start: 429 end : 429
Buffer start: 0 end : 2048
Buffer start: 0 end : 2048
Buffer start: 0 end : 2048
System.InvalidOperationException: Advancing examined to the end would cause pipe to deadlock because FlushAsync is waiting.
   at System.IO.Pipelines.ThrowHelper.ThrowInvalidOperationException_BackpressureDeadlock()
   at System.IO.Pipelines.Pipe.AdvanceReader(BufferSegment consumedSegment, Int32 consumedIndex, BufferSegment examinedSegment, Int32 examinedIndex)
   at System.IO.Pipelines.Pipe.AdvanceReader(SequencePosition& consumed, SequencePosition& examined)
   at System.IO.Pipelines.Pipe.DefaultPipeReader.AdvanceTo(SequencePosition consumed, SequencePosition examined)
   at Microsoft.AspNetCore.SignalR.HubConnectionHandler`1.DispatchMessagesAsync(HubConnectionContext connection) in C:\Users\Jon\Desktop\testproject\SignalR_2_1_\Microsoft.AspNetCore.SignalR.Core\HubConnectionHandler.cs:line 215

This would then crash the connection (i.e. uncleanly close it for all clients that the file is being pushed to). The test functionality in question is uploading an image to redis (as a blob) over HTTP, then retrieving it via SignalR to the clients. I appreciate a lot has changed, but there was no issue with this in previous (< core 2.1) code. Unsure as to what else i can do here to help but if there's anything more please let me know.

Cheers!

[davidfowl]

See #2266 (comment). This is by design.

[Jon-Murray]

Thanks David, seems my Google Fu failed me. Sorry for raising this twice so quickly to the first.

…

________________________________ From: David Fowler <[email protected]> Sent: Saturday, May 19, 2018 5:08:19 PM To: aspnet/SignalR Cc: Jonathan Murray; Author Subject: Re: [aspnet/SignalR] HubConnectionHandler Crash When Sending Large Amounts of Data (#2322) See #2266 (comment)<#2266 (comment)>. This is by design. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub<#2322 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/ACEX2wRJRR-Pft-GbR-ar-DtEzKSA-cNks5t0ENzgaJpZM4UFpMJ>.

[davidfowl]

@Jon-Murray I'd recommend using http for large file uploads until SignalR gets streaming support from client to server.

[davidfowl]

The issue I referenced outlines the current issues with large uploads and the danger in increasing the max buffer size if your application is exposed to anonymous users. I've filed this issue to look at addressing the problem https://github.com/aspnet/SignalR/issues/2320