Adds telemetry pipeline

Microsoft.FeatureManagement.sln

@@ -19,7 +19,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ConsoleApp", "examples\Cons
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "TargetingConsoleApp", "examples\TargetingConsoleApp\TargetingConsoleApp.csproj", "{6558C21E-CF20-4278-AA08-EB9D1DF29D66}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "RazorPages", "examples\RazorPages\RazorPages.csproj", "{BA29A1BB-81D5-4EB1-AF37-6ECF64AF27E2}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "RazorPages", "examples\RazorPages\RazorPages.csproj", "{BA29A1BB-81D5-4EB1-AF37-6ECF64AF27E2}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Tests.FeatureManagement.AspNetCore", "tests\Tests.FeatureManagement.AspNetCore\Tests.FeatureManagement.AspNetCore.csproj", "{FC0DC3E2-5646-4AEC-A7DB-2D6167BC3BB4}"
 EndProject

src/Microsoft.FeatureManagement/ConfigurationFeatureDefinitionProvider.cs

@@ -139,6 +139,10 @@ We support
             */
 
             RequirementType requirementType = RequirementType.Any;
+            string label = null;
+            string eTag = null;
+            bool telemetryEnabled = false;
+            Dictionary<string, string> tags = new Dictionary<string, string>();
 
             FeatureStatus featureStatus = FeatureStatus.Conditional;
 
@@ -283,6 +287,19 @@ We support
                         variants.Add(variant);
                     }
                 }
+
+                IConfigurationSection tagsSection = configurationSection.GetSection("Tags");
+                if (tagsSection.Exists())
+                {
+                    foreach (IConfigurationSection tag in tagsSection.GetChildren())
+                    {
+                        tags.Add(tag.Key, tag.Value);
+                    }
+                }
+
+                label = configurationSection["Label"];
+                eTag = configurationSection["ETag"];
+                telemetryEnabled = configurationSection.GetValue<bool>("TelemetryEnabled");
             }
 
             return new FeatureDefinition()
@@ -292,7 +309,11 @@ We support
                 RequirementType = requirementType,
                 Status = featureStatus,
                 Allocation = allocation,
-                Variants = variants
+                Variants = variants,
+                Label = label,
+                ETag = eTag,
+                TelemetryEnabled = telemetryEnabled,
+                Tags = tags
             };
         }
 

src/Microsoft.FeatureManagement/FeatureDefinition.cs

@@ -42,5 +42,25 @@ public class FeatureDefinition
         /// A list of variant definitions that specify a configuration to return when assigned.
         /// </summary>
         public IEnumerable<VariantDefinition> Variants { get; set; } = Enumerable.Empty<VariantDefinition>();
+
+        /// <summary>
+        /// Metadata that can be used to group feature flags.
+        /// </summary>
+        public string Label { get; set; }
+
+        /// <summary>
+        /// An ETag that is used to track when the feature definiton has changed.
+        /// </summary>
+        public string ETag { get; set; }
+
+        /// <summary>
+        /// A dictionary of tags used to assign additional metadata to a feature.
+        /// </summary>
+        public IReadOnlyDictionary<string, string> Tags { get; set; }
+
+        /// <summary>
+        /// A flag to enable or disable sending telemetry events to the registered <see cref="ITelemetryPublisher">.
+        /// </summary>
+        public bool TelemetryEnabled { get; set; }
     }
 }

src/Microsoft.FeatureManagement/FeatureManagementBuilderExtensions.cs

@@ -0,0 +1,40 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.FeatureManagement.Telemetry;
+using System;
+using System.Collections.Generic;
+
+namespace Microsoft.FeatureManagement
+{
+    /// <summary>
+    /// Extensions used to add feature management functionality.
+    /// </summary>
+    public static class FeatureManagementBuilderExtensions
+    {
+        /// <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

@@ -1,6 +1,10 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 //
+using Microsoft.FeatureManagement.Telemetry;
+using System;
+using System.Collections.Generic;
+
 namespace Microsoft.FeatureManagement
 {
     /// <summary>
@@ -22,5 +26,11 @@ 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; }
     }
 }