Reuse Utf8JsonWriter (#9607)

src/SignalR/common/Http.Connections.Common/src/Microsoft.AspNetCore.Http.Connections.Common.csproj

@@ -12,6 +12,7 @@
   <ItemGroup>
     <Compile Include="$(SignalRSharedSourceRoot)Utf8BufferTextWriter.cs" Link="Internal\Utf8BufferTextWriter.cs" />
     <Compile Include="$(SignalRSharedSourceRoot)SystemTextJsonExtensions.cs" Link="Internal\SystemTextJsonExtensions.cs" />
+    <Compile Include="$(SignalRSharedSourceRoot)ReusableUtf8JsonWriter.cs" Link="Internal\ReusableUtf8JsonWriter.cs" />
   </ItemGroup>
 
   <ItemGroup>

src/SignalR/common/Http.Connections.Common/src/NegotiateProtocol.cs

@@ -6,7 +6,6 @@ using System.Buffers;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
-using System.Text;
 using System.Text.Json;
 using Microsoft.AspNetCore.Internal;
 
@@ -31,12 +30,15 @@ namespace Microsoft.AspNetCore.Http.Connections
         private static ReadOnlySpan<byte> ErrorPropertyNameBytes => new byte[] { (byte)'e', (byte)'r', (byte)'r', (byte)'o', (byte)'r' };
 
         // Used to detect ASP.NET SignalR Server connection attempt
-        private const string ProtocolVersionPropertyName = "ProtocolVersion";
         private static ReadOnlySpan<byte> ProtocolVersionPropertyNameBytes => new byte[] { (byte)'P', (byte)'r', (byte)'o', (byte)'t', (byte)'o', (byte)'c', (byte)'o', (byte)'l', (byte)'V', (byte)'e', (byte)'r', (byte)'s', (byte)'i', (byte)'o', (byte)'n' };
 
         public static void WriteResponse(NegotiationResponse response, IBufferWriter<byte> output)
         {
-            using var writer = new Utf8JsonWriter(output, new JsonWriterOptions() { SkipValidation = true });
+            var reusableWriter = ReusableUtf8JsonWriter.Get(output);
+
+            try
+            {
+                var writer = reusableWriter.GetJsonWriter();
                 writer.WriteStartObject();
 
                 if (!string.IsNullOrEmpty(response.Url))
@@ -91,6 +93,11 @@ namespace Microsoft.AspNetCore.Http.Connections
                 writer.Flush();
                 Debug.Assert(writer.CurrentDepth == 0);
             }
+            finally
+            {
+                ReusableUtf8JsonWriter.Return(reusableWriter);
+            }
+        }
 
         public static NegotiationResponse ParseResponse(ReadOnlySpan<byte> content)
         {

src/SignalR/common/Protocols.Json/src/Microsoft.AspNetCore.SignalR.Protocols.Json.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <Description>Implements the SignalR Hub Protocol using System.Text.Json.</Description>
@@ -15,6 +15,7 @@
     <Compile Include="$(SignalRSharedSourceRoot)TextMessageParser.cs" Link="TextMessageParser.cs" />
     <Compile Include="$(SignalRSharedSourceRoot)Utf8BufferTextReader.cs" Link="Utf8BufferTextReader.cs" />
     <Compile Include="$(SignalRSharedSourceRoot)Utf8BufferTextWriter.cs" Link="Utf8BufferTextWriter.cs" />
+    <Compile Include="$(SignalRSharedSourceRoot)ReusableUtf8JsonWriter.cs" Link="ReusableUtf8JsonWriter.cs" />
   </ItemGroup>
 
   <ItemGroup>

src/SignalR/common/Protocols.Json/src/Protocol/JsonHubProtocol.cs

@@ -444,8 +444,11 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
 
         private void WriteMessageCore(HubMessage message, IBufferWriter<byte> stream)
         {
-            using var writer = new Utf8JsonWriter(stream);
+            var reusableWriter = ReusableUtf8JsonWriter.Get(stream);
 
+            try
+            {
+                var writer = reusableWriter.GetJsonWriter();
                 writer.WriteStartObject();
                 switch (message)
                 {
@@ -488,6 +491,11 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
                 writer.Flush();
                 Debug.Assert(writer.CurrentDepth == 0);
             }
+            finally
+            {
+                ReusableUtf8JsonWriter.Return(reusableWriter);
+            }
+        }
 
         private void WriteHeaders(Utf8JsonWriter writer, HubInvocationMessage message)
         {

src/SignalR/common/Shared/ReusableUtf8JsonWriter.cs

@@ -0,0 +1,64 @@
+// 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.Buffers;
+using System.Text.Json;
+
+namespace Microsoft.AspNetCore.Internal
+{
+    internal sealed class ReusableUtf8JsonWriter
+    {
+        [ThreadStatic]
+        private static ReusableUtf8JsonWriter _cachedInstance;
+
+        private readonly Utf8JsonWriter _writer;
+
+#if DEBUG
+        private bool _inUse;
+#endif
+
+        public ReusableUtf8JsonWriter(IBufferWriter<byte> stream)
+        {
+            _writer = new Utf8JsonWriter(stream, new JsonWriterOptions() { SkipValidation = true });
+        }
+
+        public static ReusableUtf8JsonWriter Get(IBufferWriter<byte> stream)
+        {
+            var writer = _cachedInstance;
+            if (writer == null)
+            {
+                writer = new ReusableUtf8JsonWriter(stream);
+            }
+
+            // Taken off the thread static
+            _cachedInstance = null;
+#if DEBUG
+            if (writer._inUse)
+            {
+                throw new InvalidOperationException("The writer wasn't returned!");
+            }
+
+            writer._inUse = true;
+#endif
+            writer._writer.Reset(stream);
+            return writer;
+        }
+
+        public static void Return(ReusableUtf8JsonWriter writer)
+        {
+            _cachedInstance = writer;
+
+            writer._writer.Reset();
+
+#if DEBUG
+            writer._inUse = false;
+#endif
+        }
+
+        public Utf8JsonWriter GetJsonWriter()
+        {
+            return _writer;
+        }
+    }
+}

src/SignalR/common/SignalR.Common/src/Microsoft.AspNetCore.SignalR.Common.csproj

@@ -16,6 +16,7 @@
     <Compile Include="$(SignalRSharedSourceRoot)TextMessageParser.cs" Link="Internal\TextMessageParser.cs" />
     <Compile Include="$(SignalRSharedSourceRoot)Utf8BufferTextReader.cs" Link="Internal\Utf8BufferTextReader.cs" />
     <Compile Include="$(SignalRSharedSourceRoot)Utf8BufferTextWriter.cs" Link="Internal\Utf8BufferTextWriter.cs" />
+    <Compile Include="$(SignalRSharedSourceRoot)ReusableUtf8JsonWriter.cs" Link="Internal\ReusableUtf8JsonWriter.cs" />
   </ItemGroup>
 
   <ItemGroup>

src/SignalR/common/SignalR.Common/src/Protocol/HandshakeProtocol.cs

@@ -60,7 +60,11 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="output">The output writer.</param>
         public static void WriteRequestMessage(HandshakeRequestMessage requestMessage, IBufferWriter<byte> output)
         {
-            using var writer = new Utf8JsonWriter(output, new JsonWriterOptions() { SkipValidation = true });
+            var reusableWriter = ReusableUtf8JsonWriter.Get(output);
+
+            try
+            {
+                var writer = reusableWriter.GetJsonWriter();
 
                 writer.WriteStartObject();
                 writer.WriteString(ProtocolPropertyNameBytes, requestMessage.Protocol);
@@ -68,6 +72,11 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
                 writer.WriteEndObject();
                 writer.Flush();
                 Debug.Assert(writer.CurrentDepth == 0);
+            }
+            finally
+            {
+                ReusableUtf8JsonWriter.Return(reusableWriter);
+            }
 
             TextMessageFormatter.WriteRecordSeparator(output);
         }
@@ -79,7 +88,11 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="output">The output writer.</param>
         public static void WriteResponseMessage(HandshakeResponseMessage responseMessage, IBufferWriter<byte> output)
         {
-            using var writer = new Utf8JsonWriter(output, new JsonWriterOptions() { SkipValidation = true });
+            var reusableWriter = ReusableUtf8JsonWriter.Get(output);
+
+            try
+            {
+                var writer = reusableWriter.GetJsonWriter();
 
                 writer.WriteStartObject();
                 if (!string.IsNullOrEmpty(responseMessage.Error))
@@ -92,6 +105,11 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
                 writer.WriteEndObject();
                 writer.Flush();
                 Debug.Assert(writer.CurrentDepth == 0);
+            }
+            finally
+            {
+                ReusableUtf8JsonWriter.Return(reusableWriter);
+            }
 
             TextMessageFormatter.WriteRecordSeparator(output);
         }