Telemetry Publishing via Activity & Activity Event

examples/EvaluationDataToApplicationInsights/Program.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 //
-using Microsoft.FeatureManagement.Telemetry;
 using Microsoft.FeatureManagement;
 using EvaluationDataToApplicationInsights;
 using Microsoft.ApplicationInsights.Extensibility;
@@ -31,7 +30,7 @@
 // Wire up evaluation event emission
 builder.Services.AddFeatureManagement()
     .WithTargeting<HttpContextTargetingContextAccessor>()
-    .AddTelemetryPublisher<ApplicationInsightsTelemetryPublisher>();
+    .AddAppInsightsTelemetryPublisher();
 
 //
 // Default code from .NET template below

src/Microsoft.FeatureManagement.Telemetry.ApplicationInsights/ApplicationInsightsEventPublisher.cs

@@ -0,0 +1,60 @@
+using Microsoft.ApplicationInsights;
+using System.Diagnostics;
+
+namespace Microsoft.FeatureManagement.Telemetry.ApplicationInsights
+{
+    /// <summary>
+    /// Listens to <see cref="Activity"/> events from feature management and sends them to Application Insights.
+    /// </summary>
+    internal sealed class ApplicationInsightsEventPublisher : IDisposable
+    {
+        private readonly TelemetryClient _telemetryClient;
+        private readonly ActivityListener _activityListener;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ApplicationInsightsEventPublisher"/> class.
+        /// </summary>
+        /// <param name="telemetryClient">The Application Insights telemetry client.</param>
+        public ApplicationInsightsEventPublisher(TelemetryClient telemetryClient)
+        {
+            _telemetryClient = telemetryClient ?? throw new ArgumentNullException(nameof(telemetryClient));
+
+            _activityListener = new ActivityListener
+            {
+                ShouldListenTo = (activitySource) => activitySource.Name == "Microsoft.FeatureManagement",
+                Sample = (ref ActivityCreationOptions<ActivityContext> options) => ActivitySamplingResult.AllData,
+                ActivityStopped = (activity) =>
+                {
+                    ActivityEvent? evaluationEvent = activity.Events.FirstOrDefault((activityEvent) => activityEvent.Name == "feature_flag");
+
+                    if (evaluationEvent != null && evaluationEvent.Value.Tags.Any())
+                    {
+                        HandleActivityEvent(evaluationEvent.Value);
+                    }
+                }
+            };
+
+            ActivitySource.AddActivityListener(_activityListener);
+        }
+
+        /// <summary>
+        /// Disposes the resources used by the <see cref="ApplicationInsightsEventPublisher"/>.
+        /// </summary>
+        public void Dispose()
+        {
+            _activityListener.Dispose();
+        }
+
+        private void HandleActivityEvent(ActivityEvent activityEvent)
+        {
+            var properties = new Dictionary<string, string>();
+
+            foreach (var tag in activityEvent.Tags)
+            {
+                properties[tag.Key] = tag.Value?.ToString();
+            }
+
+            _telemetryClient.TrackEvent("FeatureEvaluation", properties);
+        }
+    }
+}

src/Microsoft.FeatureManagement.Telemetry.ApplicationInsights/ApplicationInsightsHostedService.cs

@@ -0,0 +1,44 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace Microsoft.FeatureManagement.Telemetry.ApplicationInsights
+{
+    /// <summary>
+    /// A hosted service used to construct and dispose the <see cref="ApplicationInsightsEventPublisher"/>
+    /// </summary>
+    internal sealed class ApplicationInsightsHostedService : IHostedService
+    {
+        private readonly IServiceProvider _serviceProvider;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ApplicationInsightsHostedService"/> class.
+        /// </summary>
+        /// <param name="serviceProvider">The <see cref="IServiceProvider"/> to get the publisher from.</param>
+        public ApplicationInsightsHostedService(IServiceProvider serviceProvider)
+        {
+            _serviceProvider = serviceProvider ?? throw new ArgumentNullException(nameof(serviceProvider));
+        }
+
+        /// <summary>
+        /// Uses the service provider to construct a <see cref="ApplicationInsightsEventPublisher"/> which will start listening for activities.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+        public Task StartAsync(CancellationToken cancellationToken)
+        {
+            _serviceProvider.GetService<ApplicationInsightsEventPublisher>();
+
+            return Task.CompletedTask;
+        }
+
+        /// <summary>
+        /// Stops this hosted service.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+        public Task StopAsync(CancellationToken cancellationToken)
+        {
+            return Task.CompletedTask;
+        }
+    }
+}

src/Microsoft.FeatureManagement.Telemetry.ApplicationInsights/FeatureManagementBuilderExtensions.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.FeatureManagement.Telemetry.ApplicationInsights;
+
+namespace Microsoft.FeatureManagement
+{
+    /// <summary>
+    /// Extensions used to add feature management functionality.
+    /// </summary>
+    public static class FeatureManagementBuilderExtensions
+    {
+        /// <summary>
+        /// Adds the <see cref="ApplicationInsightsEventPublisher"/> using <see cref="ApplicationInsightsHostedService"/> to the feature management builder.
+        /// </summary>
+        /// <param name="builder">The feature management builder.</param>
+        /// <returns>The feature management builder.</returns>
+        public static IFeatureManagementBuilder AddAppInsightsTelemetryPublisher(this IFeatureManagementBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            if (builder.Services == null)
+            {
+                throw new ArgumentException($"The provided builder's services must not be null.", nameof(builder));
+            }
+
+            builder.Services.AddSingleton<ApplicationInsightsEventPublisher>();
+
+            if (!builder.Services.Any((ServiceDescriptor d) => d.ServiceType == typeof(IHostedService) && d.ImplementationType == typeof(ApplicationInsightsHostedService)))
+            {
+                builder.Services.Insert(0, ServiceDescriptor.Singleton<IHostedService, ApplicationInsightsHostedService>());
+            }
+
+            return builder;
+        }
+    }
+}

src/Microsoft.FeatureManagement.Telemetry.ApplicationInsights/Microsoft.FeatureManagement.Telemetry.ApplicationInsights.csproj

@@ -34,6 +34,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.ApplicationInsights" Version="2.22.0" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="8.0.0" />
   </ItemGroup>
 
   <ItemGroup>

src/Microsoft.FeatureManagement/FeatureManagementBuilderExtensions.cs

@@ -76,32 +76,5 @@ public static IFeatureManagementBuilder WithVariantService<TService>(this IFeatu
 
             return builder;
         }
-
-        /// <summary>
-        /// Adds a telemetry publisher to the feature management system.
-        /// </summary>
-        /// <param name="builder">The <see cref="IFeatureManagementBuilder"/> used to customize feature management functionality.</param>
-        /// <returns>A <see cref="IFeatureManagementBuilder"/> that can be used to customize feature management functionality.</returns>
-        public static IFeatureManagementBuilder AddTelemetryPublisher<T>(this IFeatureManagementBuilder builder) where T : ITelemetryPublisher
-        {
-            builder.AddTelemetryPublisher(sp => ActivatorUtilities.CreateInstance(sp, typeof(T)) as ITelemetryPublisher);
-
-            return builder;
-        }
-
-        private static IFeatureManagementBuilder AddTelemetryPublisher(this IFeatureManagementBuilder builder, Func<IServiceProvider, ITelemetryPublisher> factory)
-        {
-            builder.Services.Configure<FeatureManagementOptions>(options =>
-            {
-                if (options.TelemetryPublisherFactories == null)
-                {
-                    options.TelemetryPublisherFactories = new List<Func<IServiceProvider, ITelemetryPublisher>>();
-                }
-
-                options.TelemetryPublisherFactories.Add(factory);
-            });
-
-            return builder;
-        }
     }
 }

src/Microsoft.FeatureManagement/FeatureManagementOptions.cs

@@ -26,11 +26,5 @@ public class FeatureManagementOptions
         /// The default value is true.
         /// </summary>
         public bool IgnoreMissingFeatures { get; set; } = true;
-
-        /// <summary>
-        /// Holds a collection of factories that can be used to create <see cref="ITelemetryPublisher"/> instances.
-        /// This avoids the need to add the publishers to the service collection.
-        /// </summary>
-        internal ICollection<Func<IServiceProvider, ITelemetryPublisher>> TelemetryPublisherFactories { get; set; }
     }
 }