Log dropped telemetry item count on shutdown

src/OpenTelemetry/BatchExportProcessor.cs

@@ -186,7 +186,7 @@ protected override bool OnShutdown(int timeoutMilliseconds)
             this.shutdownDrainTarget = this.circularBuffer.AddedCount;
             this.shutdownTrigger.Set();
 
-            OpenTelemetrySdkEventSource.Log.DroppedExportProcessorItems(this.droppedCount);
+            OpenTelemetrySdkEventSource.Log.DroppedExportProcessorItems(this.droppedCount, this.GetType());
 
             if (timeoutMilliseconds == Timeout.Infinite)
             {

src/OpenTelemetry/Internal/OpenTelemetrySdkEventSource.cs

@@ -135,6 +135,22 @@ public void MissingPermissionsToReadEnvironmentVariable(SecurityException ex)
             }
         }
 
+        [NonEvent]
+        public void DroppedExportProcessorItems(long droppedCount, Type type)
+        {
+            if (this.IsEnabled(EventLevel.Informational, EventKeywords.All) && droppedCount <= 0)
+            {
+                this.ZeroDroppedExportProcessorItems();
+                return;
+            }
+
+            // Positive number of dropped items
+            if (this.IsEnabled(EventLevel.Warning, EventKeywords.All))
+            {
+                this.ExistsDroppedExportProcessorItems(droppedCount, type);
+            }
+        }
+
         [Event(1, Message = "Span processor queue size reached maximum. Throttling spans.", Level = EventLevel.Warning)]
         public void SpanProcessorQueueIsExhausted()
         {
@@ -309,10 +325,16 @@ public void MissingPermissionsToReadEnvironmentVariable(string exception)
             this.WriteEvent(30, exception);
         }
 
-        [Event(31, Message = "Telemetry items dropped since the start due to a full buffer: '{0}'.", Level = EventLevel.Informational)]
-        public void DroppedExportProcessorItems(long droppedCount)
+        [Event(31, Message = "Zero telemetry items were dropped.", Level = EventLevel.Informational)]
+        public void ZeroDroppedExportProcessorItems()
+        {
+            this.WriteEvent(31);
+        }
+
+        [Event(32, Message = "Telemetry items dropped: '{0}', type: '{1}'.", Level = EventLevel.Warning)]
+        public void ExistsDroppedExportProcessorItems(long droppedCount, Type type)
         {
-            this.WriteEvent(31, droppedCount);
+            this.WriteEvent(32, droppedCount, type);
         }
 
 #if DEBUG

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsTests.cs

@@ -82,6 +82,9 @@ public void OtlpExporterOptions_SetterOverridesEnvironmentVariable()
             Environment.SetEnvironmentVariable(OtlpExporterOptions.HeadersEnvVarName, "A=2,B=3");
             Environment.SetEnvironmentVariable(OtlpExporterOptions.TimeoutEnvVarName, "2000");
 
+            // If your application is targeting .NET Core 3.1, and you are using an insecure (HTTP) endpoint, the following switch must be set before adding OtlpExporter.
+            // AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true);
+
             var options = new OtlpExporterOptions
             {
                 Endpoint = new Uri("http://localhost:200"),