Log dropped telemetry item count on shutdown (#2331)

Author: mic-max

examples/Console/TestJaegerExporter.cs

@@ -87,8 +87,8 @@ internal static object RunWithActivity(string host, int port)
             {
                 sample.Start();
 
-                System.Console.WriteLine("Traces are being created and exported" +
-                    "to Jaeger in the background. Use Jaeger to view them." +
+                System.Console.WriteLine("Traces are being created and exported " +
+                    "to Jaeger in the background. Use Jaeger to view them. " +
                     "Press ENTER to stop.");
                 System.Console.ReadLine();
             }

examples/Console/TestOtlpExporter.cs

@@ -73,7 +73,7 @@ private static object RunWithActivitySource(string endpoint)
             {
                 sample.Start();
 
-                System.Console.WriteLine("Traces are being created and exported" +
+                System.Console.WriteLine("Traces are being created and exported " +
                     "to the OpenTelemetry Collector in the background. " +
                     "Press ENTER to stop.");
                 System.Console.ReadLine();

examples/Console/TestZipkinExporter.cs

@@ -50,7 +50,7 @@ internal static object Run(string zipkinUri)
             {
                 sample.Start();
 
-                System.Console.WriteLine("Traces are being created and exported" +
+                System.Console.WriteLine("Traces are being created and exported " +
                     "to Zipkin in the background. Use Zipkin to view them. " +
                     "Press ENTER to stop.");
                 System.Console.ReadLine();

src/OpenTelemetry/BatchExportProcessor.cs

@@ -186,6 +186,8 @@ protected override bool OnShutdown(int timeoutMilliseconds)
             this.shutdownDrainTarget = this.circularBuffer.AddedCount;
             this.shutdownTrigger.Set();
 
+            OpenTelemetrySdkEventSource.Log.DroppedExportProcessorItems(this.GetType().Name, this.exporter.GetType().Name, this.droppedCount);
+
             if (timeoutMilliseconds == Timeout.Infinite)
             {
                 this.exporterThread.Join();

src/OpenTelemetry/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+* `BatchExportProcessor.OnShutdown` will now log the count of dropped telemetry items.
+  ([#2331](https://github.com/open-telemetry/opentelemetry-dotnet/pull/2331))
 * Changed `CompositeProcessor<T>.OnForceFlush` to meet with the spec
   requirement. Now the SDK will invoke `ForceFlush` on all registered
   processors, even if there is a timeout.

src/OpenTelemetry/Internal/OpenTelemetrySdkEventSource.cs

@@ -135,6 +135,25 @@ public void MissingPermissionsToReadEnvironmentVariable(SecurityException ex)
             }
         }
 
+        [NonEvent]
+        public void DroppedExportProcessorItems(string exportProcessorName, string exporterName, long droppedCount)
+        {
+            if (droppedCount > 0)
+            {
+                if (this.IsEnabled(EventLevel.Warning, EventKeywords.All))
+                {
+                    this.ExistsDroppedExportProcessorItems(exportProcessorName, exporterName, droppedCount);
+                }
+            }
+            else
+            {
+                if (this.IsEnabled(EventLevel.Informational, EventKeywords.All))
+                {
+                    this.NoDroppedExportProcessorItems(exportProcessorName, exporterName);
+                }
+            }
+        }
+
         [Event(1, Message = "Span processor queue size reached maximum. Throttling spans.", Level = EventLevel.Warning)]
         public void SpanProcessorQueueIsExhausted()
         {
@@ -309,6 +328,18 @@ public void MissingPermissionsToReadEnvironmentVariable(string exception)
             this.WriteEvent(30, exception);
         }
 
+        [Event(31, Message = "'{0}' exporting to '{1}' dropped '0' items.", Level = EventLevel.Informational)]
+        public void NoDroppedExportProcessorItems(string exportProcessorName, string exporterName)
+        {
+            this.WriteEvent(31, exportProcessorName, exporterName);
+        }
+
+        [Event(32, Message = "'{0}' exporting to '{1}' dropped '{2}' item(s) due to buffer full.", Level = EventLevel.Warning)]
+        public void ExistsDroppedExportProcessorItems(string exportProcessorName, string exporterName, long droppedCount)
+        {
+            this.WriteEvent(32, exportProcessorName, exporterName, droppedCount);
+        }
+
 #if DEBUG
         public class OpenTelemetryEventListener : EventListener
         {