From 6f090e80326b0a9f64666172ff5526d5cae2789a Mon Sep 17 00:00:00 2001
From: Blake Niemyjski <bniemyjski@gmail.com>
Date: Thu, 9 Apr 2026 14:48:06 -0500
Subject: [PATCH] Fix flaky metrics test caused by DateTime.UtcNow timer
 resolution race

Replace DateTime.UtcNow timestamp ordering in RecordedMeasurement<T>
with a monotonically increasing sequence number using Interlocked.Increment.
Under coarse timer resolution (~15.6ms on Windows CI), concurrent calls to
RecordObservableInstruments() could produce measurements with identical
timestamps, causing Value<T>() to return stale data due to LINQ's stable
sort preserving insertion order for equal keys.
---
 src/Foundatio.TestHarness/Utility/InMemoryMetrics.cs | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/Foundatio.TestHarness/Utility/InMemoryMetrics.cs b/src/Foundatio.TestHarness/Utility/InMemoryMetrics.cs
index 7af094b11..f148a6b57 100644
--- a/src/Foundatio.TestHarness/Utility/InMemoryMetrics.cs
+++ b/src/Foundatio.TestHarness/Utility/InMemoryMetrics.cs
@@ -176,7 +176,7 @@ public double Value<T>(string name) where T : struct
     {
         var measurement = GetMeasurements<T>(name)
             .Where(m => m.Name == name)
-            .OrderByDescending(m => m.Timestamp)
+            .OrderByDescending(m => m.Sequence)
             .FirstOrDefault();
 
         return Convert.ToDouble(measurement.Value);
@@ -385,6 +385,10 @@ public void Dispose()
 [DebuggerDisplay("{Name}={Value}")]
 public struct RecordedMeasurement<T> where T : struct
 {
+    private static long _sequenceCounter;
+
+    private static long GetNextSequence() => Interlocked.Increment(ref _sequenceCounter);
+
     public RecordedMeasurement(Instrument instrument, T value, ref ReadOnlySpan<KeyValuePair<string, object?>> tags,
         object? state)
     {
@@ -395,7 +399,7 @@ public RecordedMeasurement(Instrument instrument, T value, ref ReadOnlySpan<KeyV
             ? ImmutableDictionary.CreateRange(tags.ToArray())
             : ImmutableDictionary<string, object?>.Empty;
         State = state;
-        Timestamp = DateTime.UtcNow;
+        Sequence = GetNextSequence();
     }
 
     public Instrument Instrument { get; }
@@ -403,5 +407,5 @@ public RecordedMeasurement(Instrument instrument, T value, ref ReadOnlySpan<KeyV
     public T Value { get; }
     public IReadOnlyDictionary<string, object?> Tags { get; }
     public object? State { get; }
-    public DateTime Timestamp { get; }
+    public long Sequence { get; }
 }