Resolving race condition when writing end stream for HEADER frame: race between hascontent data and writing the header. endstream is now always written separately.

Author: ladeak

src/CHttpServer/CHttpServer/Http2ResponseWriter.cs

@@ -1,5 +1,6 @@
 using System.Buffers;
 using System.IO;
+using System.IO.Pipelines;
 using System.Text;
 using System.Threading.Channels;
 using CHttpServer.System.Net.Http.HPack;
@@ -55,6 +56,7 @@ public async Task RunAsync(CancellationToken token)
                     await WriteTrailersAsync(request.Stream);
             }
         }
+        // TODO propagate the exception to the caller
         catch (OperationCanceledException)
         {
             // Channel is closed by the connection.
@@ -88,7 +90,8 @@ internal void ScheduleWriteTrailers(Http2Stream http2Stream) =>
     private async Task WriteDataAsync(Http2Stream stream)
     {
         long writtenCount = 0;
-        while (stream.ResponseContent.TryRead(out var readResult))
+        ReadResult readResult;
+        while (stream.ResponseContent.TryRead(out readResult))
         {
             var responseContent = readResult.Buffer;
             if (readResult.IsCanceled || (readResult.IsCompleted && responseContent.IsEmpty))
@@ -134,8 +137,7 @@ private async Task WriteHeadersAsync(Http2Stream stream)
                 throw new InvalidOperationException("Header too large");
             totalLength += writtenLength;
         }
-
-        _frameWriter.WriteResponseHeader(stream.StreamId, _buffer.AsMemory(0, totalLength), endStream: !stream.HasResponseContent);
+        _frameWriter.WriteResponseHeader(stream.StreamId, _buffer.AsMemory(0, totalLength), endStream: false);
         await _frameWriter.FlushAsync();
     }
 

src/CHttpServer/CHttpServer/Http2Stream.cs

@@ -232,8 +232,6 @@ IHeaderDictionary IHttpResponseFeature.Headers
 
     public HeaderCollection ResponseHeaders => _responseHeaders ??= new();
 
-    internal bool HasResponseContent => _responseContentPipeWriter.HasData;
-
     public void DisableBuffering()
     {
         throw new NotImplementedException();
@@ -273,8 +271,13 @@ public async Task StartAsync(CancellationToken cancellationToken = default)
         _responseWritingTask = StartResponseAsync(_cts.Token);
     }
 
-    public Task CompleteAsync() =>
-        _responseWritingTask ?? StartResponseAsync();
+    public async Task CompleteAsync()
+    {
+        var task = _responseWritingTask;
+        if (task == null)
+            await StartAsync();
+        await _responseWritingTask!;
+    }
 
     private async Task StartResponseAsync(CancellationToken cancellationToken = default)
     {
@@ -312,18 +315,14 @@ public class Http2StreamPipeWriter(PipeWriter writer, Action writeStartedCallbac
 {
     private readonly PipeWriter _writer = writer;
     private readonly Action _writeStartedCallback = writeStartedCallback;
-    private volatile bool _hasData;
     private volatile bool _completed;
     private long _unflushedBytes;
 
-    public bool HasData => _hasData;
-
     public bool IsCompleted => _completed;
 
     public override void Advance(int bytes)
     {
         _writer.Advance(bytes);
-        _hasData = true;
         _unflushedBytes += bytes;
     }