microsoft · jimmyca15 · Jan 10, 2022 · Dec 14, 2021 · Jan 7, 2022 · Jan 10, 2022
diff --git a/examples/CustomAssignmentConsoleApp/Program.cs b/examples/CustomAssignmentConsoleApp/Program.cs
@@ -35,9 +35,9 @@ public static async Task Main(string[] args)
             // Get the feature manager from application services
             using (ServiceProvider serviceProvider = services.BuildServiceProvider())
             {
-                IFeatureVariantManager variantManager = serviceProvider.GetRequiredService<IFeatureVariantManager>();
+                IDynamicFeatureManager dynamicFeatureManager = serviceProvider.GetRequiredService<IDynamicFeatureManager>();
 
-                DailyDiscountOptions discountOptions = await variantManager
+                DailyDiscountOptions discountOptions = await dynamicFeatureManager
                     .GetVariantAsync<DailyDiscountOptions>("DailyDiscount", CancellationToken.None);
 
                 //

diff --git a/examples/CustomAssignmentConsoleApp/RecurringAssigner.cs b/examples/CustomAssignmentConsoleApp/RecurringAssigner.cs
@@ -15,7 +15,7 @@ class RecurringAssigner : IFeatureVariantAssigner
     {
         public ValueTask<FeatureVariant> AssignVariantAsync(FeatureVariantAssignmentContext variantAssignmentContext, CancellationToken _)
         {
-            FeatureDefinition featureDefinition = variantAssignmentContext.FeatureDefinition;
+            DynamicFeatureDefinition featureDefinition = variantAssignmentContext.FeatureDefinition;
 
             FeatureVariant chosenVariant = null;
 

diff --git a/examples/FeatureFlagDemo/Startup.cs b/examples/FeatureFlagDemo/Startup.cs
@@ -13,6 +13,7 @@
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
 using Microsoft.FeatureManagement;
+using Microsoft.FeatureManagement.Assigners;
 using Microsoft.FeatureManagement.FeatureFilters;
 
 namespace FeatureFlagDemo

diff --git a/examples/FeatureFlagDemo/Views/Shared/_Layout.cshtml b/examples/FeatureFlagDemo/Views/Shared/_Layout.cshtml
@@ -1,7 +1,7 @@
 @using Microsoft.FeatureManagement
-@inject IFeatureVariantManager variantManager;
+@inject IDynamicFeatureManager dynamicFeatureManager;
 @{
-    DiscountBannerOptions opts = await variantManager.GetVariantAsync<DiscountBannerOptions>("DiscountBanner", Context.RequestAborted);
+    DiscountBannerOptions opts = await dynamicFeatureManager.GetVariantAsync<DiscountBannerOptions>("DiscountBanner", Context.RequestAborted);
 }
 
 <!DOCTYPE html>

diff --git a/examples/FeatureFlagDemo/appsettings.json b/examples/FeatureFlagDemo/appsettings.json
@@ -5,100 +5,102 @@
     }
   },
   "AllowedHosts": "*",
-
   // Define feature flags in config file
   "FeatureManagement": {
-
-    "Home": true,
-    "Beta": {
-      "EnabledFor": [
-        {
-          "Name": "Targeting",
-          "Parameters": { // This json object maps to a strongly typed configuration class
-            "Audience": {
-              "Users": [
-                "Jeff",
-                "Alicia"
-              ],
-              "Groups": [
-                {
-                  "Name": "Ring0",
-                  "RolloutPercentage": 80
-                },
-                {
-                  "Name": "Ring1",
-                  "RolloutPercentage": 50
-                }
-              ],
-              "DefaultRolloutPercentage": 20
+    "FeatureFlags": {
+      "Home": true,
+      "Beta": {
+        "EnabledFor": [
+          {
+            "Name": "Targeting",
+            "Parameters": { // This json object maps to a strongly typed configuration class
+              "Audience": {
+                "Users": [
+                  "Jeff",
+                  "Alicia"
+                ],
+                "Groups": [
+                  {
+                    "Name": "Ring0",
+                    "RolloutPercentage": 80
+                  },
+                  {
+                    "Name": "Ring1",
+                    "RolloutPercentage": 50
+                  }
+                ],
+                "DefaultRolloutPercentage": 20
+              }
             }
           }
-        }
-      ]
-    },
-    "CustomViewData":  {
-      "EnabledFor": [
-        {
-          "Name": "Browser",
-          "Parameters": {
-            "AllowedBrowsers": [ "Chrome", "Edge" ]
+        ]
+      },
+      "CustomViewData": {
+        "EnabledFor": [
+          {
+            "Name": "Browser",
+            "Parameters": {
+              "AllowedBrowsers": [ "Chrome", "Edge" ]
+            }
           }
-        }
-      ]
-    },
-    "ContentEnhancement": {
-      "EnabledFor": [
-        {
-          "Name": "TimeWindow",
-          "Parameters": {
-            "Start": "Wed, 01 May 2019 13:59:59 GMT",
-            "End": "Mon, 01 July 2019 00:00:00 GMT"
+        ]
+      },
+      "ContentEnhancement": {
+        "EnabledFor": [
+          {
+            "Name": "TimeWindow",
+            "Parameters": {
+              "Start": "Wed, 01 May 2019 13:59:59 GMT",
+              "End": "Mon, 01 July 2019 00:00:00 GMT"
+            }
           }
-        }
-      ]
-    },
-    "EnhancedPipeline": {
-      "EnabledFor": [
-        {
-          "Name": "Microsoft.Percentage",
-          "Parameters": {
-            "Value": 50
+        ]
+      },
+      "EnhancedPipeline": {
+        "EnabledFor": [
+          {
+            "Name": "Microsoft.Percentage",
+            "Parameters": {
+              "Value": 50
+            }
           }
-        }
-      ]
+        ]
+      }
     },
-    "DiscountBanner": {
-      "Assigner": "Targeting",
-      "Variants": [
-        {
-          "Default": true,
-          "Name": "Big",
-          "ConfigurationReference": "DiscountBanner:Big"
-        },
-        {
-          "Name": "Small",
-          "ConfigurationReference": "DiscountBanner:Small",
-          "AssignmentParameters": {
-            "Audience": {
-              "Users": [
-                "Jeff",
-                "Alicia"
-              ],
-              "Groups": [
-                {
-                  "Name": "Ring0",
-                  "RolloutPercentage": 80
-                },
-                {
-                  "Name": "Ring1",
-                  "RolloutPercentage": 50
-                }
-              ],
-              "DefaultRolloutPercentage": 20
+    "DynamicFeatures": {
+      "DiscountBanner": {
+        "Assigner": "Targeting",
+        "Variants": [
+          {
+            "Default": true,
+            "Name": "Big",
+            "ConfigurationReference": "DiscountBanner:Big"
+          },
+          {
+            "Name": "Small",
+            "ConfigurationReference": "DiscountBanner:Small",
+            "AssignmentParameters": {
+              "Audience": {
+                "Users": [
+                  "Jeff",
+                  "Alicia"
+                ],
+                "Groups": [
+                  {
+                    "Name": "Ring0",
+                    "RolloutPercentage": 80
+                  },
+                  {
+                    "Name": "Ring1",
+                    "RolloutPercentage": 50
+                  }
+                ],
+                "DefaultRolloutPercentage": 20
+              }
             }
           }
-        }
-      ]
+        ]
+      }
     }
   },
   "DiscountBanner": {

diff --git a/examples/TargetingConsoleApp/Program.cs b/examples/TargetingConsoleApp/Program.cs
@@ -5,6 +5,7 @@
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.FeatureManagement;
+using Microsoft.FeatureManagement.Assigners;
 using Microsoft.FeatureManagement.FeatureFilters;
 using System;
 using System.Collections.Generic;
@@ -40,7 +41,7 @@ public static async Task Main(string[] args)
             using (ServiceProvider serviceProvider = services.BuildServiceProvider())
             {
                 IFeatureManager featureManager = serviceProvider.GetRequiredService<IFeatureManager>();
-                IFeatureVariantManager variantManager = serviceProvider.GetRequiredService<IFeatureVariantManager>();
+                IDynamicFeatureManager dynamicFeatureManager = serviceProvider.GetRequiredService<IDynamicFeatureManager>();
 
                 //
                 // We'll simulate a task to run on behalf of each known user
@@ -76,7 +77,7 @@ public static async Task Main(string[] args)
 
                     //
                     // Retrieve feature variant using targeting
-                    CartOptions cartOptions = await variantManager
+                    CartOptions cartOptions = await dynamicFeatureManager
                         .GetVariantAsync<CartOptions, TargetingContext>(
                             DynamicFeatureName,
                             targetingContext,

diff --git a/src/Microsoft.FeatureManagement/ConfigurationDynamicFeatureDefinitionProvider.cs b/src/Microsoft.FeatureManagement/ConfigurationDynamicFeatureDefinitionProvider.cs
@@ -0,0 +1,144 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Primitives;
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.FeatureManagement
+{
+    /// <summary>
+    /// A feature definition provider that pulls dynamic feature definitions from the .NET Core <see cref="IConfiguration"/> system.
+    /// </summary>
+    sealed class ConfigurationDynamicFeatureDefinitionProvider : IDynamicFeatureDefinitionProvider, IDisposable
+    {
+        private const string FeatureManagementSectionName = "FeatureManagement";
+        private const string DynamicFeatureDefinitionsSectionName= "DynamicFeatures";
+        private const string FeatureVariantsSectionName = "Variants";
+        private readonly IConfiguration _configuration;
+        private readonly ConcurrentDictionary<string, DynamicFeatureDefinition> _dynamicFeatureDefinitions;
+        private IDisposable _changeSubscription;
+        private int _stale = 0;
+
+        public ConfigurationDynamicFeatureDefinitionProvider(IConfiguration configuration)
+        {
+            _configuration = configuration ?? throw new ArgumentNullException(nameof(configuration));
+            _dynamicFeatureDefinitions = new ConcurrentDictionary<string, DynamicFeatureDefinition>();
+
+            _changeSubscription = ChangeToken.OnChange(
+                () => _configuration.GetReloadToken(),
+                () => _stale = 1);
+        }
+
+        public void Dispose()
+        {
+            _changeSubscription?.Dispose();
+
+            _changeSubscription = null;
+        }
+
+        public Task<DynamicFeatureDefinition> GetDynamicFeatureDefinitionAsync(string featureName, CancellationToken cancellationToken = default)
+        {
+            if (featureName == null)
+            {
+                throw new ArgumentNullException(nameof(featureName));
+            }
+
+            EnsureFresh();
+
+            //
+            // Query by feature name
+            DynamicFeatureDefinition definition = _dynamicFeatureDefinitions.GetOrAdd(featureName, (name) => ReadDynamicFeatureDefinition(name));
+
+            return Task.FromResult(definition);
+        }
+
+        //
+        // The async key word is necessary for creating IAsyncEnumerable.
+        // The need to disable this warning occurs when implementaing async stream synchronously. 
+#pragma warning disable CS1998 // Async method lacks 'await' operators and will run synchronously
+        public async IAsyncEnumerable<DynamicFeatureDefinition> GetAllDynamicFeatureDefinitionsAsync([EnumeratorCancellation] CancellationToken cancellationToken)
+#pragma warning restore CS1998 // Async method lacks 'await' operators and will run synchronously
+        {
+            EnsureFresh();
+
+            //
+            // Iterate over all features registered in the system at initial invocation time
+            foreach (IConfigurationSection featureSection in GetDynamicFeatureDefinitionSections())
+            {
+                //
+                // Underlying IConfigurationSection data is dynamic so latest feature definitions are returned
+                yield return _dynamicFeatureDefinitions.GetOrAdd(featureSection.Key, (_) => ReadDynamicFeatureDefinition(featureSection));
+            }
+        }
+
+        private DynamicFeatureDefinition ReadDynamicFeatureDefinition(string featureName)
+        {
+            IConfigurationSection configuration = GetDynamicFeatureDefinitionSections()
+                                                    .FirstOrDefault(section => section.Key.Equals(featureName, StringComparison.OrdinalIgnoreCase));
+
+            if (configuration == null)
+            {
+                return null;
+            }
+
+            return ReadDynamicFeatureDefinition(configuration);
+        }
+
+        private DynamicFeatureDefinition ReadDynamicFeatureDefinition(IConfigurationSection configurationSection)
+        {
+            Debug.Assert(configurationSection != null);
+
+            var variants = new List<FeatureVariant>();
+
+            foreach (IConfigurationSection section in configurationSection.GetSection(FeatureVariantsSectionName).GetChildren())
+            {
+                if (int.TryParse(section.Key, out int _) && !string.IsNullOrEmpty(section[nameof(FeatureVariant.Name)]))
+                {
+                    variants.Add(new FeatureVariant
+                    {
+                        Default = section.GetValue<bool>(nameof(FeatureVariant.Default)),
+                        Name = section.GetValue<string>(nameof(FeatureVariant.Name)),
+                        ConfigurationReference = section.GetValue<string>(nameof(FeatureVariant.ConfigurationReference)),
+                        AssignmentParameters = section.GetSection(nameof(FeatureVariant.AssignmentParameters))
+                    });
+                }
+            }
+
+            return new DynamicFeatureDefinition()
+            {
+                Name = configurationSection.Key,
+                Variants = variants,
+                Assigner = configurationSection.GetValue<string>(nameof(DynamicFeatureDefinition.Assigner))
+            };
+        }
+
+        private IEnumerable<IConfigurationSection> GetDynamicFeatureDefinitionSections()
+        {
+            //
+            // Look for feature definitions under the "FeatureManagement" section
+            IConfiguration featureManagementSection = _configuration.GetChildren().Any(s => s.Key.Equals(FeatureManagementSectionName, StringComparison.OrdinalIgnoreCase)) ?
+                _configuration.GetSection(FeatureManagementSectionName) :
+                _configuration;
+
+            return featureManagementSection
+                .GetSection(DynamicFeatureDefinitionsSectionName)
+                .GetChildren();
+        }
+
+        private void EnsureFresh()
+        {
+            if (Interlocked.Exchange(ref _stale, 0) != 0)
+            {
+                _dynamicFeatureDefinitions.Clear();
+            }
+        }
+    }
+}