From b45b8a9a1272ea91924cc644fd6765ed44778ec6 Mon Sep 17 00:00:00 2001
From: ImoutoChan <kirirrin@gmail.com>
Date: Tue, 31 Oct 2023 06:19:14 +0300
Subject: [PATCH] Check isSampled parameter in UpdateWithExemplar method
 (#5004)

---
 src/OpenTelemetry/CHANGELOG.md           |  4 +++
 src/OpenTelemetry/Metrics/MetricPoint.cs | 44 +++++++++++++++---------
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/src/OpenTelemetry/CHANGELOG.md b/src/OpenTelemetry/CHANGELOG.md
index 30856d74dfc..e5d3afac461 100644
--- a/src/OpenTelemetry/CHANGELOG.md
+++ b/src/OpenTelemetry/CHANGELOG.md
@@ -11,6 +11,10 @@
   `autoGenerateServiceInstanceId` is `true`.
   ([#4988](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4988))
 
+* Fixed a bug where isSampled parameter wasn't properly checked in certain cases
+  within the `UpdateWithExemplar` method of `MetricPoint`.
+  ([#4851](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5004))
+
 ## 1.7.0-alpha.1
 
 Released 2023-Oct-16
diff --git a/src/OpenTelemetry/Metrics/MetricPoint.cs b/src/OpenTelemetry/Metrics/MetricPoint.cs
index 48f726f4754..831f027b3eb 100644
--- a/src/OpenTelemetry/Metrics/MetricPoint.cs
+++ b/src/OpenTelemetry/Metrics/MetricPoint.cs
@@ -499,11 +499,14 @@ internal void UpdateWithExemplar(long number, ReadOnlySpan<KeyValuePair<string,
 
                     this.runningValue.AsLong = number;
 
-                    Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
+                    if (isSampled)
+                    {
+                        Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
 
-                    // TODO: Need to ensure that the lock is always released.
-                    // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
-                    this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                        // TODO: Need to ensure that the lock is always released.
+                        // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
+                        this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                    }
 
                     ReleaseLock(ref this.mpComponents!.IsCriticalSectionOccupied);
 
@@ -516,11 +519,14 @@ internal void UpdateWithExemplar(long number, ReadOnlySpan<KeyValuePair<string,
 
                     this.runningValue.AsLong = number;
 
-                    Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
+                    if (isSampled)
+                    {
+                        Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
 
-                    // TODO: Need to ensure that the lock is always released.
-                    // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
-                    this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                        // TODO: Need to ensure that the lock is always released.
+                        // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
+                        this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                    }
 
                     ReleaseLock(ref this.mpComponents!.IsCriticalSectionOccupied);
 
@@ -717,11 +723,14 @@ internal void UpdateWithExemplar(double number, ReadOnlySpan<KeyValuePair<string
                         this.runningValue.AsDouble = number;
                     }
 
-                    Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
+                    if (isSampled)
+                    {
+                        Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
 
-                    // TODO: Need to ensure that the lock is always released.
-                    // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
-                    this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                        // TODO: Need to ensure that the lock is always released.
+                        // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
+                        this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                    }
 
                     ReleaseLock(ref this.mpComponents!.IsCriticalSectionOccupied);
 
@@ -737,11 +746,14 @@ internal void UpdateWithExemplar(double number, ReadOnlySpan<KeyValuePair<string
                         this.runningValue.AsDouble = number;
                     }
 
-                    Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
+                    if (isSampled)
+                    {
+                        Debug.Assert(this.mpComponents.ExemplarReservoir != null, "ExemplarReservoir was null");
 
-                    // TODO: Need to ensure that the lock is always released.
-                    // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
-                    this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                        // TODO: Need to ensure that the lock is always released.
+                        // A custom implementation of `ExemplarReservoir.Offer` might throw an exception.
+                        this.mpComponents.ExemplarReservoir!.Offer(number, tags);
+                    }
 
                     ReleaseLock(ref this.mpComponents!.IsCriticalSectionOccupied);