Only call PrepareDateValues if not already called for tick

src/Microsoft.AspNetCore.Server.Kestrel/Http/DateHeaderValueManager.cs

@@ -13,15 +13,15 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
     /// </summary>
     public class DateHeaderValueManager : IDisposable
     {
+        private static readonly byte[] _datePreambleBytes = Encoding.ASCII.GetBytes("\r\nDate: ");
+
         private readonly ISystemClock _systemClock;
         private readonly TimeSpan _timeWithoutRequestsUntilIdle;
         private readonly TimeSpan _timerInterval;
+        private readonly object _timerLocker = new object();
+
+        private DateHeaderValues _dateValues;
 
-        private volatile string _dateValue;
-        private volatile bool _activeDateBytes;
-        private readonly byte[] _dateBytes0 = Encoding.ASCII.GetBytes("\r\nDate: DDD, dd mmm yyyy hh:mm:ss GMT");
-        private readonly byte[] _dateBytes1 = Encoding.ASCII.GetBytes("\r\nDate: DDD, dd mmm yyyy hh:mm:ss GMT");
-        private object _timerLocker = new object();
         private volatile bool _isDisposed = false;
         private volatile bool _hadRequestsSinceLastTimerTick = false;
         private Timer _dateValueTimer;
@@ -55,19 +55,15 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
         /// Returns a value representing the current server date/time for use in the HTTP "Date" response header
         /// in accordance with http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.18
         /// </summary>
-        /// <returns>The value.</returns>
+        /// <returns>The value in string and byte[] format.</returns>
-        public virtual string GetDateHeaderValue()
+        public DateHeaderValues GetDateHeaderValues()
         {
-            _hadRequestsSinceLastTimerTick = true;
+            if (!_hadRequestsSinceLastTimerTick)
-            PrepareDateValues();
+            {
-            return _dateValue;
+                PrepareDateValues();
-        }
+            }
 
-        public byte[] GetDateHeaderValueBytes()
+            return _dateValues;
-        {
-            _hadRequestsSinceLastTimerTick = true;
-            PrepareDateValues();
-            return _activeDateBytes ? _dateBytes0 : _dateBytes1;
         }
 
         /// <summary>
@@ -78,6 +74,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
             if (!_isDisposed)
             {
                 _isDisposed = true;
+                _hadRequestsSinceLastTimerTick = false;
 
                 lock (_timerLocker)
                 {
@@ -125,6 +122,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
                     {
                         _timerIsRunning = false;
                         _dateValueTimer.Change(Timeout.Infinite, Timeout.Infinite);
+                        _hadRequestsSinceLastTimerTick = false;
                     }
                 }
             }
@@ -158,16 +156,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
         /// </summary>
         private void PrepareDateValues()
         {
-            if (_isDisposed)
+            _hadRequestsSinceLastTimerTick = !_isDisposed;
+            if (!_timerIsRunning)
             {
-                SetDateValues(_systemClock.UtcNow);
+                StartTimer();
-            }
-            else
-            {
-                if (!_timerIsRunning)
-                {
-                    StartTimer();
-                }
             }
         }
 
@@ -178,9 +170,23 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
         private void SetDateValues(DateTimeOffset value)
         {
             // See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.18 for required format of Date header
-            _dateValue = value.ToString(Constants.RFC1123DateFormat);
+            var dateValue = value.ToString(Constants.RFC1123DateFormat);
-            Encoding.ASCII.GetBytes(_dateValue, 0, _dateValue.Length, !_activeDateBytes ? _dateBytes0 : _dateBytes1, "\r\nDate: ".Length);
+            var dateBytes = new byte[_datePreambleBytes.Length + dateValue.Length];
-            _activeDateBytes = !_activeDateBytes;
+            Buffer.BlockCopy(_datePreambleBytes, 0, dateBytes, 0, _datePreambleBytes.Length);
+            Encoding.ASCII.GetBytes(dateValue, 0, dateValue.Length, dateBytes, _datePreambleBytes.Length);
+
+            var dateValues = new DateHeaderValues()
+            {
+                Bytes = dateBytes,
+                String = dateValue
+            };
+            Volatile.Write(ref _dateValues, dateValues);
+        }
+
+        public class DateHeaderValues
+        {
+            public byte[] Bytes;
+            public string String;
         }
     }
 }

src/Microsoft.AspNetCore.Server.Kestrel/Http/Frame.cs

@@ -589,12 +589,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
 
                     var responseHeaders = _frameHeaders.ResponseHeaders;
                     responseHeaders.Reset();
-                    responseHeaders.SetRawDate(
+                    var dateHeaderValues = DateHeaderValueManager.GetDateHeaderValues();
-                        DateHeaderValueManager.GetDateHeaderValue(),
+                    responseHeaders.SetRawDate(dateHeaderValues.String, dateHeaderValues.Bytes);
-                        DateHeaderValueManager.GetDateHeaderValueBytes());
+                    responseHeaders.SetRawServer("Kestrel", Headers.BytesServer);
-                    responseHeaders.SetRawServer(
-                        "Kestrel",
-                        Headers.BytesServer);
                     responseHeaders.SetRawContentLength("0", _bytesContentLengthZero);
 
                     ResponseHeaders = responseHeaders;

src/Microsoft.AspNetCore.Server.Kestrel/Infrastructure/HttpComponentFactory.cs

@@ -78,9 +78,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Infrastructure
 
         public void Initialize(DateHeaderValueManager dateValueManager)
         {
-            ResponseHeaders.SetRawDate(
+            var dateHeaderValues = dateValueManager.GetDateHeaderValues();
-                dateValueManager.GetDateHeaderValue(),
+            ResponseHeaders.SetRawDate(dateHeaderValues.String, dateHeaderValues.Bytes);
-                dateValueManager.GetDateHeaderValueBytes());
             ResponseHeaders.SetRawServer("Kestrel", BytesServer);
         }
 

test/Microsoft.AspNetCore.Server.KestrelTests/DateHeaderValueManagerTests.cs

@@ -27,7 +27,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
 
             try
             {
-                result = dateHeaderValueManager.GetDateHeaderValue();
+                result = dateHeaderValueManager.GetDateHeaderValues().String;
             }
             finally
             {
@@ -54,9 +54,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
 
             try
             {
-                result1 = dateHeaderValueManager.GetDateHeaderValue();
+                result1 = dateHeaderValueManager.GetDateHeaderValues().String;
                 systemClock.UtcNow = future;
-                result2 = dateHeaderValueManager.GetDateHeaderValue();
+                result2 = dateHeaderValueManager.GetDateHeaderValues().String;
             }
             finally
             {
@@ -85,11 +85,11 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
 
             try
             {
-                result1 = dateHeaderValueManager.GetDateHeaderValue();
+                result1 = dateHeaderValueManager.GetDateHeaderValues().String;
                 systemClock.UtcNow = future;
                 // Wait for longer than the idle timeout to ensure the timer is stopped
                 await Task.Delay(TimeSpan.FromSeconds(1));
-                result2 = dateHeaderValueManager.GetDateHeaderValue();
+                result2 = dateHeaderValueManager.GetDateHeaderValues().String;
             }
             finally
             {
@@ -114,10 +114,10 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
             var timerInterval = TimeSpan.FromSeconds(10);
             var dateHeaderValueManager = new DateHeaderValueManager(systemClock, timeWithoutRequestsUntilIdle, timerInterval);
 
-            var result1 = dateHeaderValueManager.GetDateHeaderValue();
+            var result1 = dateHeaderValueManager.GetDateHeaderValues().String;
             dateHeaderValueManager.Dispose();
             systemClock.UtcNow = future;
-            var result2 = dateHeaderValueManager.GetDateHeaderValue();
+            var result2 = dateHeaderValueManager.GetDateHeaderValues().String;
             
             Assert.Equal(now.ToString(Constants.RFC1123DateFormat), result1);
             Assert.Equal(future.ToString(Constants.RFC1123DateFormat), result2);

test/Microsoft.AspNetCore.Server.KestrelTests/TestDateHeaderValueManager.cs

@@ -1,16 +0,0 @@
-// 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 Microsoft.AspNetCore.Server.Kestrel.Http;
-
-namespace Microsoft.AspNetCore.Server.KestrelTests
-{
-    public class TestDateHeaderValueManager : DateHeaderValueManager
-    {
-        public override string GetDateHeaderValue()
-        {
-            return DateTimeOffset.UtcNow.ToString("r");
-        }
-    }
-}

test/Microsoft.AspNetCore.Server.KestrelTests/TestServiceContext.cs

@@ -20,7 +20,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
             AppLifetime = new LifetimeNotImplemented();
             Log = new TestKestrelTrace();
             ThreadPool = new LoggingThreadPool(Log);
-            DateHeaderValueManager = new TestDateHeaderValueManager();
+            DateHeaderValueManager = new DateHeaderValueManager();
 
             ServerOptions = new KestrelServerOptions();
             ServerOptions.ShutdownTimeout = TimeSpan.FromSeconds(5);