Reuse Http2MessageBody (#19629)

Author: JamesNK

src/Servers/Kestrel/Core/src/Internal/Http/Http1MessageBody.cs

@@ -16,8 +16,7 @@ internal abstract class Http1MessageBody : MessageBody
         protected readonly Http1Connection _context;
         protected bool _completed;
 
-        protected Http1MessageBody(Http1Connection context)
-            : base(context)
+        protected Http1MessageBody(Http1Connection context) : base(context)
         {
             _context = context;
         }

src/Servers/Kestrel/Core/src/Internal/Http/MessageBody.cs

@@ -73,6 +73,17 @@ public virtual Task StopAsync()
 
         protected virtual Task OnStopAsync() => Task.CompletedTask;
 
+        public virtual void Reset()
+        {
+            _send100Continue = true;
+            _consumedBytes = 0;
+            _stopped = false;
+            _timingEnabled = false;
+            _backpressure = false;
+            _alreadyTimedBytes = 0;
+            _examinedUnconsumedBytes = 0;
+        }
+
         protected void TryProduceContinue()
         {
             if (_send100Continue)

src/Servers/Kestrel/Core/src/Internal/Http2/Http2MessageBody.cs

@@ -15,7 +15,7 @@ internal sealed class Http2MessageBody : MessageBody
         private readonly Http2Stream _context;
         private ReadResult _readResult;
 
-        private Http2MessageBody(Http2Stream context)
+        public Http2MessageBody(Http2Stream context)
             : base(context)
         {
             _context = context;
@@ -46,14 +46,10 @@ protected override void OnDataRead(long bytesRead)
             AddAndCheckConsumedBytes(bytesRead);
         }
 
-        public static MessageBody For(Http2Stream context)
+        public override void Reset()
         {
-            if (context.ReceivedEmptyRequestBody)
-            {
-                return ZeroContentLengthClose;
-            }
-
-            return new Http2MessageBody(context);
+            base.Reset();
+            _readResult = default;
         }
 
         public override void AdvanceTo(SequencePosition consumed)

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Stream.cs

@@ -23,6 +23,7 @@ internal abstract partial class Http2Stream : HttpProtocol, IThreadPoolWorkItem,
         private Http2OutputProducer _http2Output;
         private StreamInputFlowControl _inputFlowControl;
         private StreamOutputFlowControl _outputFlowControl;
+        private Http2MessageBody _messageBody;
 
         private bool _decrementCalled;
 
@@ -170,7 +171,23 @@ protected override string CreateRequestId()
             => StringUtilities.ConcatAsHexSuffix(ConnectionId, ':', (uint)StreamId);
 
         protected override MessageBody CreateMessageBody()
-            => Http2MessageBody.For(this);
+        {
+            if (ReceivedEmptyRequestBody)
+            {
+                return MessageBody.ZeroContentLengthClose;
+            }
+
+            if (_messageBody != null)
+            {
+                _messageBody.Reset();
+            }
+            else
+            {
+                _messageBody = new Http2MessageBody(this);
+            }
+
+            return _messageBody;
+        }
 
         // Compare to Http1Connection.OnStartLine
         protected override bool TryParseRequest(ReadResult result, out bool endConnection)