issue #180 - Add OnEventWrittenHandler extensibility, to DiagnosticSo…

src/DiagnosticSourceListener/DiagnosticSourceListenerSubscription.cs

@@ -8,15 +8,14 @@ namespace Microsoft.ApplicationInsights.DiagnosticSourceListener
 {
     using System;
     using System.Collections.Generic;
-    using System.Globalization;
-    using Microsoft.ApplicationInsights.DataContracts;
 
     internal class DiagnosticSourceListenerSubscription : IObserver<KeyValuePair<string, object>>
     {
         private readonly string listenerName;
         private readonly TelemetryClient telemetryClient;
+        private readonly OnEventWrittenHandler onEventWrittenHandler;
 
-        public DiagnosticSourceListenerSubscription(string listenerName, TelemetryClient telemetryClient)
+        public DiagnosticSourceListenerSubscription(string listenerName, TelemetryClient telemetryClient, OnEventWrittenHandler onEventWrittenHandler)
         {
             if (listenerName == null)
             {
@@ -28,8 +27,14 @@ public DiagnosticSourceListenerSubscription(string listenerName, TelemetryClient
                 throw new ArgumentNullException(nameof(telemetryClient));
             }
 
+            if (onEventWrittenHandler == null)
+            {
+                throw new ArgumentNullException(nameof(onEventWrittenHandler));
+            }
+
             this.listenerName = listenerName;
             this.telemetryClient = telemetryClient;
+            this.onEventWrittenHandler = onEventWrittenHandler;
         }
 
         public void OnCompleted()
@@ -46,25 +51,14 @@ public void OnError(Exception error)
         /// <param name="event">The event (message and payload) from the diagnostic source.</param>
         public void OnNext(KeyValuePair<string, object> @event)
         {
-            var message = @event.Key;
-            var payload = @event.Value;
-
-            var telemetry = new TraceTelemetry(message, SeverityLevel.Information);
-            telemetry.Properties.Add("DiagnosticSource", this.listenerName);
-
-            // Transfer properties from payload to telemetry
-            if (payload != null)
+            try
             {
-                foreach (var property in DeclaredPropertiesCache.GetDeclaredProperties(payload))
-                {
-                    if (!property.IsSpecialName)
-                    {
-                        telemetry.Properties.Add(property.Name, Convert.ToString(property.GetValue(payload), CultureInfo.InvariantCulture));
-                    }
-                }
+                this.onEventWrittenHandler(this.listenerName, @event.Key, @event.Value, this.telemetryClient);
+            }
+            catch (Exception ex)
+            {
+                this.telemetryClient.TrackException(ex);
             }
-
-            this.telemetryClient.TrackTrace(telemetry);
         }
     }
 }

src/DiagnosticSourceListener/DiagnosticSourceTelemetryModule.cs

@@ -9,20 +9,54 @@ namespace Microsoft.ApplicationInsights.DiagnosticSourceListener
     using System;
     using System.Collections.Generic;
     using System.Diagnostics;
+    using System.Globalization;
     using System.Threading;
+    using Microsoft.ApplicationInsights.DataContracts;
     using Microsoft.ApplicationInsights.Extensibility;
     using Microsoft.ApplicationInsights.Extensibility.Implementation;
     using Microsoft.ApplicationInsights.Implementation;
 
+    /// <summary>
+    /// Delegate to apply custom formatting to Application Insights trace telemetry from the Diagnostics Source data.
+    /// </summary>
+    /// <param name="sourceName">Name of the DiagnosticsSource (as implemented by a DiagnosticsListener).</param>
+    /// <param name="message">Name of the event.</param>
+    /// <param name="payload">Data associated with the event.</param>
+    /// <param name="client">Telemetry client to report telemetry to.</param>
+    public delegate void OnEventWrittenHandler(string sourceName, string message, object payload, TelemetryClient client);
+
     /// <summary>
     /// A module to forward diagnostic source events to Application Insights.
     /// </summary>
     public sealed class DiagnosticSourceTelemetryModule : IObserver<DiagnosticListener>, ITelemetryModule, IDisposable
     {
+        private readonly OnEventWrittenHandler onEventWrittenHandler;
+
         private TelemetryClient client;
         private IDisposable allDiagnosticListenersSubscription;
         private List<IDisposable> diagnosticListenerSubscriptions;
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DiagnosticSourceTelemetryModule"/> class.
+        /// </summary>
+        public DiagnosticSourceTelemetryModule() : this(Track)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DiagnosticSourceTelemetryModule"/> class.
+        /// </summary>
+        /// <param name="onEventWrittenHandler">Action to be executed each time an event is written to format and send via the configured <see cref="TelemetryClient"/></param>
+        public DiagnosticSourceTelemetryModule(OnEventWrittenHandler onEventWrittenHandler)
+        {
+            if (onEventWrittenHandler == null)
+            {
+                throw new ArgumentNullException(nameof(onEventWrittenHandler));
+            }
+
+            this.onEventWrittenHandler = onEventWrittenHandler;
+        }
+
         /// <summary>
         /// Gets the list of DiagnosticSource listening requests (information about which DiagnosticSources should be traced).
         /// </summary>
@@ -90,11 +124,31 @@ void IObserver<DiagnosticListener>.OnNext(DiagnosticListener listener)
                         this.diagnosticListenerSubscriptions = new List<IDisposable>();
                     }
 
-                    var subscription = new DiagnosticSourceListenerSubscription(listener.Name, this.client);
+                    var subscription = new DiagnosticSourceListenerSubscription(listener.Name, this.client, this.onEventWrittenHandler);
                     this.diagnosticListenerSubscriptions.Add(listener.Subscribe(subscription));
                     break;
                 }
             }
         }
+
+        private static void Track(string sourceName, string message, object payload, TelemetryClient client)
+        {
+            var telemetry = new TraceTelemetry(message, SeverityLevel.Information);
+            telemetry.Properties.Add("DiagnosticSource", sourceName);
+
+            // Transfer properties from payload to telemetry
+            if (payload != null)
+            {
+                foreach (var property in DeclaredPropertiesCache.GetDeclaredProperties(payload))
+                {
+                    if (!property.IsSpecialName)
+                    {
+                        telemetry.Properties.Add(property.Name, Convert.ToString(property.GetValue(payload), CultureInfo.InvariantCulture));
+                    }
+                }
+            }
+
+            client.TrackTrace(telemetry);
+        }
     }
 }

test/DiagnosticSourceListener.netcoreapp10.Tests/DiagnosticSourceTelemetryModuleTests.cs

@@ -98,6 +98,31 @@ public void HandlesPropertiesWithNullValues()
             }
         }
 
+        [TestMethod]
+        public void CallsOnEventWrittenHandler()
+        {
+            OnEventWrittenHandler onEventWrittenHandler = (sourceName, message, payload, client) =>
+            {
+                var traceTelemetry = new TraceTelemetry("CustomPayloadProperties", SeverityLevel.Verbose);
+                traceTelemetry.Properties.Add("CustomPayloadProperties", "true");
+                client.Track(traceTelemetry);
+            };
+
+            using (var module = new DiagnosticSourceTelemetryModule(onEventWrittenHandler))
+            {
+                var testDiagnosticSource = new TestDiagnosticSource();
+                var listeningRequest = new DiagnosticSourceListeningRequest(testDiagnosticSource.Name);
+                module.Sources.Add(listeningRequest);
+
+                module.Initialize(GetTestTelemetryConfiguration());
+
+                testDiagnosticSource.Write("Hey!", new { Prop1 = 1234 });
+
+                TraceTelemetry telemetry = (TraceTelemetry)this.adapterHelper.Channel.SentItems.First();
+                Assert.IsTrue(telemetry.Properties.All(kvp => kvp.Key.Equals("CustomPayloadProperties") && kvp.Value.Equals("true")));
+            }
+        }
+
         private TelemetryConfiguration GetTestTelemetryConfiguration(bool resetChannel = true)
         {
             var configuration = new TelemetryConfiguration();