chore(): Added explicit logging for mTLS HttpClient creation failures via a new event source entry

Author: sandy2008

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/OpenTelemetryProtocolExporterEventSource.cs

@@ -309,5 +309,21 @@ internal void MtlsServerCertificateValidationFailed(string subject, string error
         Level = EventLevel.Informational)]
     internal void MtlsConfigurationEnabled(string clientCertificateSubject) =>
         this.WriteEvent(33, clientCertificateSubject);
+
+    [NonEvent]
+    internal void MtlsHttpClientCreationFailed(Exception ex)
+    {
+        if (Log.IsEnabled(EventLevel.Error, EventKeywords.All))
+        {
+            this.MtlsHttpClientCreationFailed(ex.ToInvariantString());
+        }
+    }
+
+    [Event(
+        34,
+        Message = "Failed to create mTLS HttpClient. Exception: {0}",
+        Level = EventLevel.Error)]
+    internal void MtlsHttpClientCreationFailed(string exception) =>
+        this.WriteEvent(34, exception);
 #endif
 }

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/OtlpMtlsHttpClientFactory.cs

@@ -28,9 +28,7 @@ public static HttpClient CreateMtlsHttpClient(
 
         if (!mtlsOptions.IsEnabled)
         {
-            throw new InvalidOperationException(
-                "mTLS options must include a client or CA certificate path."
-            );
+            throw new InvalidOperationException("mTLS options must include a client or CA certificate path.");
         }
 
         HttpClientHandler? handler = null;
@@ -122,6 +120,7 @@ public static HttpClient CreateMtlsHttpClient(
             // Dispose handler if something went wrong
             handler?.Dispose();
 
+            OpenTelemetryProtocolExporterEventSource.Log.MtlsHttpClientCreationFailed(ex);
             OpenTelemetryProtocolExporterEventSource.Log.ExportMethodException(ex);
             throw;
         }