Add custom processor example and consoleexporter extension method. (#754)

samples/Exporters/Console/TestConsoleActivity.cs

@@ -16,8 +16,11 @@
 
 using System;
 using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
 using OpenTelemetry.Exporter.Console;
 using OpenTelemetry.Trace.Configuration;
+using OpenTelemetry.Trace.Export;
 
 namespace Samples
 {
@@ -26,10 +29,13 @@ namespace Samples
         internal static object Run(ConsoleActivityOptions options)
         {
             // Enable OpenTelemetry for the source "MyCompany.MyProduct.MyWebServer"
-            // and use Console exporter
+            // and use a single pipeline with a custom MyProcessor, and Console exporter.
             using var openTelemetry = OpenTelemetrySdk.EnableOpenTelemetry(
                 (builder) => builder.AddActivitySource("MyCompany.MyProduct.MyWebServer")
-                .UseConsoleActivityExporter(opt => opt.DisplayAsJson = options.DisplayAsJson));
+                .AddProcessorPipeline(
+                    (p) =>
+                    p.AddProcessor((next) => new MyProcessor(next))
+                    .UseConsoleActivityExporter(opt => opt.DisplayAsJson = options.DisplayAsJson)));
 
             // The above line is required only in Applications
             // which decide to use OT.
@@ -91,5 +97,42 @@ namespace Samples
 
             return null;
         }
+
+        internal class MyProcessor : ActivityProcessor
+        {
+            private ActivityProcessor next;
+
+            public MyProcessor(ActivityProcessor next)
+            {
+                this.next = next;
+            }
+
+            public override void OnEnd(Activity activity)
+            {
+                this.next.OnEnd(activity);
+            }
+
+            public override void OnStart(Activity activity)
+            {
+                if (activity.IsAllDataRequested)
+                {
+                    if (activity.Kind == ActivityKind.Server)
+                    {
+                        activity.AddTag("customServerTag", "Custom Tag Value for server");
+                    }
+                    else if (activity.Kind == ActivityKind.Client)
+                    {
+                        activity.AddTag("customClientTag", "Custom Tag Value for Client");
+                    }
+                }
+
+                this.next.OnStart(activity);
+            }
+
+            public override Task ShutdownAsync(CancellationToken cancellationToken)
+            {
+                return this.next.ShutdownAsync(cancellationToken);
+            }
+        }
     }
 }

src/OpenTelemetry.Exporter.Console/OpenTelemetryBuilderExtensions.cs

@@ -22,7 +22,7 @@ namespace OpenTelemetry.Exporter.Console
     public static class OpenTelemetryBuilderExtensions
     {
         /// <summary>
-        /// Registers a ConsoleActivity exporter.
+        /// Adds new processing pipeline and registers a ConsoleActivity exporter to it.
         /// </summary>
         /// <param name="builder">Open Telemetry builder to use.</param>
         /// <param name="configure">Exporter configuration options.</param>
@@ -44,5 +44,29 @@ namespace OpenTelemetry.Exporter.Console
             var consoleExporter = new ConsoleActivityExporter(exporterOptions);
             return builder.AddProcessorPipeline(pipeline => pipeline.SetExporter(consoleExporter));
         }
+
+        /// <summary>
+        /// Registers a ConsoleActivity exporter to a processing pipeline.
+        /// </summary>
+        /// <param name="builder">ActivityProcessorPipelineBuilder to use.</param>
+        /// <param name="configure">Exporter configuration options.</param>
+        /// <returns>The instance of <see cref="ActivityProcessorPipelineBuilder"/> to chain the calls.</returns>
+        public static ActivityProcessorPipelineBuilder UseConsoleActivityExporter(this ActivityProcessorPipelineBuilder builder, Action<ConsoleActivityExporterOptions> configure)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            if (configure == null)
+            {
+                throw new ArgumentNullException(nameof(configure));
+            }
+
+            var exporterOptions = new ConsoleActivityExporterOptions();
+            configure(exporterOptions);
+            var consoleExporter = new ConsoleActivityExporter(exporterOptions);
+            return builder.SetExporter(consoleExporter);
+        }
     }
 }