Start pooling Http2Streams (#18601)

src/Servers/Kestrel/Core/src/Internal/Http/Http1Connection.cs

@@ -37,8 +37,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         private int _remainingRequestHeadersBytesAllowed;
 
         public Http1Connection(HttpConnectionContext context)
-            : base(context)
         {
+            Initialize(context);
+
             _context = context;
             _parser = ServiceContext.HttpParser;
             _keepAliveTicks = ServerOptions.Limits.KeepAliveTimeout.Ticks;

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

@@ -37,7 +37,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         private Stack<KeyValuePair<Func<object, Task>, object>> _onCompleted;
 
         private readonly object _abortLock = new object();
-        private volatile bool _connectionAborted;
+        protected volatile bool _connectionAborted;
         private bool _preventRequestAbortedCancellation;
         private CancellationTokenSource _abortedCts;
         private CancellationToken? _manuallySetRequestAbortToken;
@@ -66,7 +66,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 
         private long _responseBytesWritten;
 
-        private readonly HttpConnectionContext _context;
+        private HttpConnectionContext _context;
         private RouteValueDictionary _routeValues;
         private Endpoint _endpoint;
 
@@ -75,12 +75,16 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         private Stream _requestStreamInternal;
         private Stream _responseStreamInternal;
 
-        public HttpProtocol(HttpConnectionContext context)
+        public void Initialize(HttpConnectionContext context)
         {
             _context = context;
 
             ServerOptions = ServiceContext.ServerOptions;
-            HttpRequestHeaders = new HttpRequestHeaders(reuseHeaderValues: !ServerOptions.DisableStringReuse);
+
+            Reset();
+
+            HttpRequestHeaders.ReuseHeaderValues = !ServerOptions.DisableStringReuse;
+
             HttpResponseControl = this;
         }
 
@@ -97,7 +101,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         protected IKestrelTrace Log => ServiceContext.Log;
         private DateHeaderValueManager DateHeaderValueManager => ServiceContext.DateHeaderValueManager;
         // Hold direct reference to ServerOptions since this is used very often in the request processing path
-        protected KestrelServerOptions ServerOptions { get; }
+        protected KestrelServerOptions ServerOptions { get; set; }
         protected string ConnectionId => _context.ConnectionId;
 
         public string ConnectionIdFeature { get; set; }
@@ -306,7 +310,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 
         public bool HasResponseCompleted => _requestProcessingStatus == RequestProcessingStatus.ResponseCompleted;
 
-        protected HttpRequestHeaders HttpRequestHeaders { get; }
+        protected HttpRequestHeaders HttpRequestHeaders { get; } = new HttpRequestHeaders();
 
         protected HttpResponseHeaders HttpResponseHeaders { get; } = new HttpResponseHeaders();
 
@@ -361,7 +365,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             var remoteEndPoint = RemoteEndPoint;
             RemoteIpAddress = remoteEndPoint?.Address;
             RemotePort = remoteEndPoint?.Port ?? 0;
-
             var localEndPoint = LocalEndPoint;
             LocalIpAddress = localEndPoint?.Address;
             LocalPort = localEndPoint?.Port ?? 0;
@@ -373,6 +376,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             RequestHeaders = HttpRequestHeaders;
             ResponseHeaders = HttpResponseHeaders;
             RequestTrailers.Clear();
+            ResponseTrailers?.Reset();
             RequestTrailersAvailable = false;
 
             _isLeasedMemoryInvalid = true;

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

@@ -14,14 +14,15 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 {
     internal sealed partial class HttpRequestHeaders : HttpHeaders
     {
-        private readonly bool _reuseHeaderValues;
         private long _previousBits = 0;
 
         public HttpRequestHeaders(bool reuseHeaderValues = true)
         {
-            _reuseHeaderValues = reuseHeaderValues;
+            ReuseHeaderValues = reuseHeaderValues;
         }
 
+        public bool ReuseHeaderValues { get; set; }
+
         public void OnHeadersComplete()
         {
             var bitsToClear = _previousBits & ~_bits;
@@ -40,7 +41,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 
         protected override void ClearFast()
         {
-            if (!_reuseHeaderValues)
+            if (!ReuseHeaderValues)
             {
                 // If we aren't reusing headers clear them all
                 Clear(_bits);

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Connection.cs

@@ -8,11 +8,9 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.IO.Pipelines;
-using System.Net.Http;
 using System.Net.Http.HPack;
 using System.Runtime.CompilerServices;
 using System.Security.Authentication;
-using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
@@ -23,7 +21,6 @@ using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2.FlowControl;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure;
 using Microsoft.Extensions.Logging;
-using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
 {
@@ -67,6 +64,11 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
         private int _gracefulCloseInitiator;
         private int _isClosed;
 
+        private Http2StreamStack _streamPool;
+
+        internal const int InitialStreamPoolSize = 5;
+        internal const int MaxStreamPoolSize = 40;
+
         public Http2Connection(HttpConnectionContext context)
         {
             var httpLimits = context.ServiceContext.ServerOptions.Limits;
@@ -106,6 +108,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
             _serverSettings.HeaderTableSize = (uint)http2Limits.HeaderTableSize;
             _serverSettings.MaxHeaderListSize = (uint)httpLimits.MaxRequestHeadersTotalSize;
             _serverSettings.InitialWindowSize = (uint)http2Limits.InitialStreamWindowSize;
+
+            // Start pool off at a smaller size if the max number of streams is less than the InitialStreamPoolSize
+            _streamPool = new Http2StreamStack(Math.Min(InitialStreamPoolSize, http2Limits.MaxStreamsPerConnection));
+
             _inputTask = ReadInputAsync();
         }
 
@@ -554,7 +560,31 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
                 }
 
                 // Start a new stream
-                _currentHeadersStream = new Http2Stream<TContext>(application, new Http2StreamContext
+                _currentHeadersStream = GetStream(application);
+
+                _headerFlags = _incomingFrame.HeadersFlags;
+
+                var headersPayload = payload.Slice(0, _incomingFrame.HeadersPayloadLength); // Minus padding
+                return DecodeHeadersAsync(_incomingFrame.HeadersEndHeaders, headersPayload);
+            }
+        }
+
+        private Http2Stream GetStream<TContext>(IHttpApplication<TContext> application)
+        {
+            if (_streamPool.TryPop(out var stream))
+            {
+                stream.InitializeWithExistingContext(_incomingFrame.StreamId);
+                return stream;
+            }
+
+            return new Http2Stream<TContext>(
+                application,
+                CreateHttp2StreamContext());
+        }
+
+        private Http2StreamContext CreateHttp2StreamContext()
+        {
+            return new Http2StreamContext
             {
                 ConnectionId = ConnectionId,
                 StreamId = _incomingFrame.StreamId,
@@ -570,13 +600,14 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
                 ConnectionInputFlowControl = _inputFlowControl,
                 ConnectionOutputFlowControl = _outputFlowControl,
                 TimeoutControl = TimeoutControl,
-                });
+            };
+        }
 
-                _currentHeadersStream.Reset();
-                _headerFlags = _incomingFrame.HeadersFlags;
-
-                var headersPayload = payload.Slice(0, _incomingFrame.HeadersPayloadLength); // Minus padding
-                return DecodeHeadersAsync(_incomingFrame.HeadersEndHeaders, headersPayload);
+        private void ReturnStream(Http2Stream stream)
+        {
+            if (_streamPool.Count < MaxStreamPoolSize)
+            {
+                _streamPool.Push(stream);
             }
         }
 
@@ -1028,6 +1059,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
                     }
 
                     _streams.Remove(stream.StreamId);
+                    ReturnStream(stream);
                 }
                 else
                 {
@@ -1054,6 +1086,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
                 }
 
                 _streams.Remove(stream.StreamId);
+                ReturnStream(stream);
             }
         }
 
@@ -1400,6 +1433,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
             Unknown = 0x40000000
         }
 
+
         private static class GracefulCloseInitiator
         {
             public const int None = 0;

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

@@ -19,22 +19,30 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
 {
     internal abstract partial class Http2Stream : HttpProtocol, IThreadPoolWorkItem
     {
-        private readonly Http2StreamContext _context;
-        private readonly Http2OutputProducer _http2Output;
-        private readonly StreamInputFlowControl _inputFlowControl;
-        private readonly StreamOutputFlowControl _outputFlowControl;
+        private Http2StreamContext _context;
+        private Http2OutputProducer _http2Output;
+        private StreamInputFlowControl _inputFlowControl;
+        private StreamOutputFlowControl _outputFlowControl;
 
         private bool _decrementCalled;
-        public Pipe RequestBodyPipe { get; }
+
+        public Pipe RequestBodyPipe { get; set; }
 
         internal long DrainExpirationTicks { get; set; }
 
         private StreamCompletionFlags _completionState;
         private readonly object _completionLock = new object();
 
-        public Http2Stream(Http2StreamContext context)
-            : base(context)
+        public void Initialize(Http2StreamContext context)
         {
+            base.Initialize(context);
+
+            _decrementCalled = false;
+            _completionState = StreamCompletionFlags.None;
+            InputRemaining = null;
+            RequestBodyStarted = false;
+            DrainExpirationTicks = 0;
+
             _context = context;
 
             _inputFlowControl = new StreamInputFlowControl(
@@ -60,6 +68,12 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
             Output = _http2Output;
         }
 
+        public void InitializeWithExistingContext(int streamId)
+        {
+            _context.StreamId = streamId;
+            Initialize(_context);
+        }
+
         public int StreamId => _context.StreamId;
 
         public long? InputRemaining { get; internal set; }
@@ -82,6 +96,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
 
         protected override void OnReset()
         {
+            _keepAlive = true;
+            _connectionAborted = false;
+
             ResetHttp2Features();
         }
 

src/Servers/Kestrel/Core/src/Internal/Http2/Http2StreamOfT.cs

@@ -11,8 +11,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
     {
         private readonly IHttpApplication<TContext> _application;
 
-        public Http2Stream(IHttpApplication<TContext> application, Http2StreamContext context) : base(context)
+        public Http2Stream(IHttpApplication<TContext> application, Http2StreamContext context) 
         {
+            Initialize(context);
             _application = application;
         }
 

src/Servers/Kestrel/Core/src/Internal/Http2/Http2StreamStack.cs

@@ -0,0 +1,74 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
+{
+    // See https://github.com/dotnet/runtime/blob/master/src/libraries/System.IO.Pipelines/src/System/IO/Pipelines/BufferSegmentStack.cs
+    internal struct Http2StreamStack
+    {
+        private Http2StreamAsValueType[] _array;
+        private int _size;
+
+        public Http2StreamStack(int size)
+        {
+            _array = new Http2StreamAsValueType[size];
+            _size = 0;
+        }
+
+        public int Count => _size;
+
+        public bool TryPop(out Http2Stream result)
+        {
+            int size = _size - 1;
+            Http2StreamAsValueType[] array = _array;
+
+            if ((uint)size >= (uint)array.Length)
+            {
+                result = default;
+                return false;
+            }
+
+            _size = size;
+            result = array[size];
+            array[size] = default;
+            return true;
+        }
+
+        // Pushes an item to the top of the stack.
+        public void Push(Http2Stream item)
+        {
+            int size = _size;
+            Http2StreamAsValueType[] array = _array;
+
+            if ((uint)size < (uint)array.Length)
+            {
+                array[size] = item;
+                _size = size + 1;
+            }
+            else
+            {
+                PushWithResize(item);
+            }
+        }
+
+        // Non-inline from Stack.Push to improve its code quality as uncommon path
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private void PushWithResize(Http2Stream item)
+        {
+            Array.Resize(ref _array, 2 * _array.Length);
+            _array[_size] = item;
+            _size++;
+        }
+
+        private readonly struct Http2StreamAsValueType
+        {
+            private readonly Http2Stream _value;
+            private Http2StreamAsValueType(Http2Stream value) => _value = value;
+            public static implicit operator Http2StreamAsValueType(Http2Stream s) => new Http2StreamAsValueType(s);
+            public static implicit operator Http2Stream(Http2StreamAsValueType s) => s._value;
+        }
+    }
+}

src/Servers/Kestrel/Core/src/Internal/Http3/Http3Stream.cs

@@ -31,8 +31,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http3
         private bool _receivedHeaders;
         public Pipe RequestBodyPipe { get; }
 
-        public Http3Stream(Http3Connection http3Connection, HttpConnectionContext context) : base(context)
+        public Http3Stream(Http3Connection http3Connection, HttpConnectionContext context) 
         {
+            Initialize(context);
             // First, determine how we know if an Http3stream is unidirectional or bidirectional
             var httpLimits = context.ServiceContext.ServerOptions.Limits;
             var http3Limits = httpLimits.Http3;
@@ -115,7 +116,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http3
         {
             try
             {
-
                 while (_isClosed == 0)
                 {
                     var result = await Input.ReadAsync();

src/Servers/Kestrel/Core/test/Http1ConnectionTests.cs

@@ -69,7 +69,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             };
 
             _http1Connection = new TestHttp1Connection(_http1ConnectionContext);
-            _http1Connection.Reset();
         }
 
         public void Dispose()

src/Servers/Kestrel/Core/test/HttpProtocolFeatureCollectionTests.cs

@@ -249,8 +249,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
 
         private class TestHttp2Stream : Http2Stream
         {
-            public TestHttp2Stream(Http2StreamContext context) : base(context)
+            public TestHttp2Stream(Http2StreamContext context) 
             {
+                Initialize(context);
             }
 
             public override void Execute()

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http2/Http2StreamTests.cs

@@ -1866,6 +1866,58 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             Assert.Equal("0", _decodedHeaders[HeaderNames.ContentLength]);
         }
 
+        [Fact]
+        public async Task ResponseTrailers_WorksAcrossMultipleStreams_Cleared()
+        {
+            await InitializeConnectionAsync(context =>
+            {
+                Assert.True(context.Response.SupportsTrailers(), "SupportsTrailers");
+
+                var trailers = context.Features.Get<IHttpResponseTrailersFeature>().Trailers;
+                Assert.False(trailers.IsReadOnly);
+
+                context.Response.AppendTrailer("CustomName", "Custom Value");
+                return Task.CompletedTask;
+            });
+
+            await StartStreamAsync(1, _browserRequestHeaders, endStream: true);
+
+            var headersFrame1 = await ExpectAsync(Http2FrameType.HEADERS,
+                withLength: 55,
+                withFlags: (byte)(Http2HeadersFrameFlags.END_HEADERS),
+                withStreamId: 1);
+            var trailersFrame1 = await ExpectAsync(Http2FrameType.HEADERS,
+                withLength: 25,
+                withFlags: (byte)(Http2HeadersFrameFlags.END_HEADERS | Http2HeadersFrameFlags.END_STREAM),
+                withStreamId: 1);
+
+            await StartStreamAsync(3, _browserRequestHeaders, endStream: true);
+
+            var headersFrame2 = await ExpectAsync(Http2FrameType.HEADERS,
+                withLength: 55,
+                withFlags: (byte)(Http2HeadersFrameFlags.END_HEADERS),
+                withStreamId: 3);
+
+            var trailersFrame2 = await ExpectAsync(Http2FrameType.HEADERS,
+                withLength: 25,
+                withFlags: (byte)(Http2HeadersFrameFlags.END_HEADERS | Http2HeadersFrameFlags.END_STREAM),
+                withStreamId: 3);
+
+            await StopConnectionAsync(expectedLastStreamId: 3, ignoreNonGoAwayFrames: false);
+
+            _hpackDecoder.Decode(trailersFrame1.PayloadSequence, endHeaders: true, handler: this);
+
+            Assert.Single(_decodedHeaders);
+            Assert.Equal("Custom Value", _decodedHeaders["CustomName"]);
+
+            _decodedHeaders.Clear();
+
+            _hpackDecoder.Decode(trailersFrame2.PayloadSequence, endHeaders: true, handler: this);
+
+            Assert.Single(_decodedHeaders);
+            Assert.Equal("Custom Value", _decodedHeaders["CustomName"]);
+        }
+
         [Fact]
         public async Task ResponseTrailers_WithData_Sent()
         {