Record exception in HttpClient native instrumentation (#115959)

* Record exception in HttpClient native instrumentation

* Fix Possible null reference argument for parameter 'exception'

* Fix test

* Fix

* Fix

* Update links

* Set exception event timestamp to match activity end time

* Remove trailing space

* Add assert

---------

Co-authored-by: joegoldman2 <[email protected]>

Author: joegoldman2

src/libraries/System.Net.Http/src/System/Net/Http/DiagnosticsHandler.cs

@@ -207,8 +207,16 @@ await _innerHandler.SendAsync(request, cancellationToken).ConfigureAwait(false)
                             activity.SetTag("error.type", errorType);
 
                             // The presence of error.type indicates that the conditions for setting Error status are also met.
-                            // https://github.com/open-telemetry/semantic-conventions/blob/v1.26.0/docs/http/http-spans.md#status
+                            // https://github.com/open-telemetry/semantic-conventions/blob/v1.34.0/docs/http/http-spans.md#status
                             activity.SetStatus(ActivityStatusCode.Error);
+
+                            if (exception is not null)
+                            {
+                                // Records the exception as per https://github.com/open-telemetry/opentelemetry-specification/blob/v1.45.0/specification/trace/exceptions.md.
+                                // Add the exception event with a timestamp matching the activity's end time
+                                // to ensure it falls within the activity's duration.
+                                activity.AddException(exception, timestamp: activity.StartTimeUtc + activity.Duration);
+                            }
                         }
                     }
 

src/libraries/System.Net.Http/tests/FunctionalTests/DiagnosticsTests.cs

@@ -784,6 +784,14 @@ static async Task RunTest(string useVersion, string testAsync, string failureTyp
                     ActivityAssert.HasTag(conn, "error.type", "name_resolution_error");
                     ActivityAssert.HasTag(wait, "error.type", "name_resolution_error");
 
+                    ActivityEvent evt = req.Events.Single(e => e.Name == "exception");
+                    Dictionary<string, object?> tags = evt.Tags.ToDictionary(t => t.Key, t => t.Value);
+                    Assert.Contains("exception.type", tags.Keys);
+                    Assert.Contains("exception.message", tags.Keys);
+                    Assert.Contains("exception.stacktrace", tags.Keys);
+                    Assert.Equal(typeof(HttpRequestException).FullName, tags["exception.type"]);
+                    Assert.InRange(evt.Timestamp - req.StartTimeUtc, new TimeSpan(1), req.Duration);
+
                     // Whether System.Net.Quic uses System.Net.Dns is an implementation detail.
                     if (version != HttpVersion30)
                     {
@@ -803,6 +811,14 @@ static async Task RunTest(string useVersion, string testAsync, string failureTyp
                     ActivityAssert.HasTag(conn, "error.type", "connection_error");
                     ActivityAssert.HasTag(wait, "error.type", "connection_error");
 
+                    ActivityEvent evt = req.Events.Single(e => e.Name == "exception");
+                    Dictionary<string, object?> tags = evt.Tags.ToDictionary(t => t.Key, t => t.Value);
+                    Assert.Contains("exception.type", tags.Keys);
+                    Assert.Contains("exception.message", tags.Keys);
+                    Assert.Contains("exception.stacktrace", tags.Keys);
+                    Assert.Equal(typeof(HttpRequestException).FullName, tags["exception.type"]);
+                    Assert.InRange(evt.Timestamp - req.StartTimeUtc, new TimeSpan(1), req.Duration);
+
                     if (version != HttpVersion30)
                     {
                         Activity sock = socketRecorder.VerifyActivityRecordedOnce();