Simplify!

Author: MihaZupan

src/ReverseProxy/Service/Proxy/HttpProxy.cs

@@ -34,8 +34,6 @@ internal class HttpProxy : IHttpProxy
         private readonly ILogger _logger;
         private readonly IClock _clock;
 
-        private static readonly TimeoutCtsPool _ctsPool = new(DefaultTimeout, resolution: TimeSpan.FromSeconds(2));
-
         public HttpProxy(ILogger<HttpProxy> logger, IClock clock)
         {
             _logger = logger ?? throw new ArgumentNullException(nameof(logger));
@@ -125,7 +123,7 @@ public async Task ProxyAsync(
                 // :: Step 4: Send the outgoing request using HttpClient
                 HttpResponseMessage destinationResponse;
 
-                var requestTimeoutSource = _ctsPool.Rent(requestOptions?.Timeout ?? DefaultTimeout, requestAborted);
+                var requestTimeoutSource = PooledCTS.Rent(requestOptions?.Timeout ?? DefaultTimeout, requestAborted);
                 var requestTimeoutToken = requestTimeoutSource.Token;
                 try
                 {

src/ReverseProxy/Utilities/PooledCTS.cs

@@ -0,0 +1,56 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+#nullable enable
+
+using System;
+using System.Collections.Concurrent;
+using System.Threading;
+
+namespace Yarp.ReverseProxy.Utilities
+{
+    internal sealed class PooledCTS : CancellationTokenSource
+    {
+        private static readonly ConcurrentQueue<PooledCTS> _sharedSources = new();
+
+        private static readonly Action<object?> _linkedTokenCancelDelegate = static s =>
+        {
+            ((CancellationTokenSource)s!).Cancel(throwOnFirstException: false);
+        };
+
+        private CancellationTokenRegistration _registration;
+
+        public static PooledCTS Rent(TimeSpan timeout, CancellationToken linkedToken)
+        {
+            if (!_sharedSources.TryDequeue(out var cts))
+            {
+                cts = new PooledCTS();
+            }
+
+            cts._registration = linkedToken.UnsafeRegister(_linkedTokenCancelDelegate, cts);
+
+            cts.CancelAfter(timeout);
+
+            return cts;
+        }
+
+        public void Return()
+        {
+            _registration.Dispose();
+            _registration = default;
+
+            // TODO: Replace CancelAfter(Timeout.Infinite) & IsCancellationRequested with TryReset in 6.0+
+
+            CancelAfter(Timeout.Infinite);
+
+            if (IsCancellationRequested)
+            {
+                Dispose();
+            }
+            else
+            {
+                _sharedSources.Enqueue(this);
+            }
+        }
+    }
+}