[AspNet.Telemetry] Fix end of time (#3171)

Author: Kielek

src/OpenTelemetry.Instrumentation.AspNet.TelemetryHttpModule/ActivityDateTimeHelper.cs

@@ -0,0 +1,82 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// https://github.com/dotnet/runtime/blob/75662173e3918f2176b74e467dc8e41d4f01d4d4/src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.DateTime.netfx.cs
+
+// Adjusted to our coding standards and moved to separate class
+
+using System.Diagnostics;
+
+namespace OpenTelemetry.Instrumentation.AspNet;
+
+internal static class ActivityDateTimeHelper
+{
+#pragma warning disable CA1823 // suppress unused field warning, as it's used to keep the timer alive
+    private static readonly Timer SyncTimeUpdater = InitializeSyncTimer();
+#pragma warning restore CA1823
+    private static readonly double TickFrequency = (double)TimeSpan.TicksPerSecond / Stopwatch.Frequency;
+
+    private static TimeSync timeSync = new();
+
+    /// <summary>
+    /// Returns high resolution (1 DateTime tick) current UTC DateTime.
+    /// </summary>
+    /// <returns>High resolution UTC DateTime.</returns>
+    internal static DateTime GetUtcNow()
+    {
+        // DateTime.UtcNow accuracy on .NET Framework is ~16ms, this method
+        // uses combination of Stopwatch and DateTime to calculate accurate UtcNow.
+
+        var tmp = timeSync;
+
+        // Timer ticks need to be converted to DateTime ticks
+        long dateTimeTicksDiff = (long)((Stopwatch.GetTimestamp() - tmp.SyncStopwatchTicks) * TickFrequency);
+
+        // DateTime.AddSeconds (or Milliseconds) rounds value to 1 ms, use AddTicks to prevent it
+        return tmp.SyncUtcNow.AddTicks(dateTimeTicksDiff);
+    }
+
+    private static void Sync()
+    {
+        // wait for DateTime.UtcNow update to the next granular value
+        Thread.Sleep(1);
+        timeSync = new TimeSync();
+    }
+
+    [System.Security.SecuritySafeCritical]
+    private static Timer InitializeSyncTimer()
+    {
+        Timer timer;
+
+        // Don't capture the current ExecutionContext and its AsyncLocals onto the timer causing them to live forever
+        bool restoreFlow = false;
+        try
+        {
+            if (!ExecutionContext.IsFlowSuppressed())
+            {
+                ExecutionContext.SuppressFlow();
+                restoreFlow = true;
+            }
+
+            timer = new Timer(static _ => Sync(), null, 0, 7_200_000); // 2 hours
+        }
+        finally
+        {
+            // Restore the current ExecutionContext
+            if (restoreFlow)
+            {
+                ExecutionContext.RestoreFlow();
+            }
+        }
+
+        return timer;
+    }
+
+    private sealed class TimeSync
+    {
+        public readonly DateTime SyncUtcNow = DateTime.UtcNow;
+        public readonly long SyncStopwatchTicks = Stopwatch.GetTimestamp();
+    }
+}

src/OpenTelemetry.Instrumentation.AspNet.TelemetryHttpModule/ActivityHelper.cs

@@ -120,7 +120,7 @@ public static void StopAspNetActivity(TextMapPropagator textMapPropagator, Activ
         // Note that the activity must not be stopped before the callback is called.
         if (aspNetActivity.Duration == TimeSpan.Zero)
         {
-            aspNetActivity.SetEndTime(DateTime.UtcNow);
+            aspNetActivity.SetEndTime(ActivityDateTimeHelper.GetUtcNow());
         }
 
         try

src/OpenTelemetry.Instrumentation.AspNet.TelemetryHttpModule/CHANGELOG.md

@@ -11,6 +11,9 @@
   responsible for providing function returning `Activity`.
   ([#3151](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/3151))
 
+* Fixed an inaccurate span end of time.
+  ([#3171](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/3171))
+
 ## 1.12.0-beta.2
 
 Released 2025-Sep-18