Populate feature flag telemetry metadata when feature flag telemetry is enabled

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationProvider.cs

@@ -916,7 +916,7 @@ private void SetData(IDictionary<string, string> data)
                     continue;
                 }
 
-                IEnumerable<KeyValuePair<string, string>> kvs = await adapter.ProcessKeyValue(setting, _logger, cancellationToken).ConfigureAwait(false);
+                IEnumerable<KeyValuePair<string, string>> kvs = await adapter.ProcessKeyValue(setting, AppConfigurationEndpoint, _logger, cancellationToken).ConfigureAwait(false);
 
                 if (kvs != null)
                 {

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureKeyVaultReference/AzureKeyVaultKeyValueAdapter.cs

@@ -27,7 +27,7 @@ public AzureKeyVaultKeyValueAdapter(AzureKeyVaultSecretProvider secretProvider)
         /// <summary> Uses the Azure Key Vault secret provider to resolve Key Vault references retrieved from Azure App Configuration. </summary>
         /// <param KeyValue ="IKeyValue">  inputs the IKeyValue </param>
         /// returns the keyname and actual value
-        public async Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Logger logger, CancellationToken cancellationToken)
+        public async Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Uri endpoint, Logger logger, CancellationToken cancellationToken)
         {
             KeyVaultSecretReference secretRef;
 

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Extensions/BytesExtensions.cs

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using System.Text;
+using System;
+
+namespace Microsoft.Extensions.Configuration.AzureAppConfiguration.Extensions
+{
+    internal static class BytesExtensions
+    {
+        /// <summary>
+        /// Converts a byte array to Base64URL string with optional padding ('=') characters removed.
+        /// Base64 description: https://datatracker.ietf.org/doc/html/rfc4648.html#section-4
+        /// </summary>
+        public static string ToBase64Url(this byte[] bytes)
+        {
+            string bytesBase64 = Convert.ToBase64String(bytes);
+
+            int indexOfEquals = bytesBase64.IndexOf("=");
+
+            // Remove all instances of "=" at the end of the string that were added as padding
+            int stringBuilderCapacity = indexOfEquals != -1 ? indexOfEquals : bytesBase64.Length;
+
+            StringBuilder stringBuilder = new StringBuilder(stringBuilderCapacity);
+
+            // Construct Base64URL string by replacing characters in Base64 conversion that are not URL safe
+            for (int i = 0; i < stringBuilderCapacity; i++)
+            {
+                if (bytesBase64[i] == '+')
+                {
+                    stringBuilder.Append('-');
+                }
+                else if (bytesBase64[i] == '/')
+                {
+                    stringBuilder.Append('_');
+                }
+                else
+                {
+                    stringBuilder.Append(bytesBase64[i]);
+                }
+            }
+
+            return stringBuilder.ToString();
+        }
+    }
+}

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/FeatureManagement/FeatureManagementConstants.cs

@@ -31,5 +31,8 @@ internal class FeatureManagementConstants
         public const string From = "From";
         public const string To = "To";
         public const string Seed = "Seed";
+        public const string ETag = "ETag";
+        public const string FeatureFlagId = "FeatureFlagId";
+        public const string FeatureFlagReference = "FeatureFlagReference";
     }
 }

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/FeatureManagement/FeatureManagementKeyValueAdapter.cs

@@ -2,9 +2,12 @@
 // Licensed under the MIT license.
 //
 using Azure.Data.AppConfiguration;
+using Microsoft.Extensions.Configuration.AzureAppConfiguration.Extensions;
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
 using System.Text.Json;
 using System.Threading;
 using System.Threading.Tasks;
@@ -20,7 +23,7 @@ public FeatureManagementKeyValueAdapter(FeatureFilterTracing featureFilterTracin
             _featureFilterTracing = featureFilterTracing ?? throw new ArgumentNullException(nameof(featureFilterTracing));
         }
 
-        public Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Logger logger, CancellationToken cancellationToken)
+        public Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Uri endpoint, Logger logger, CancellationToken cancellationToken)
         {
             FeatureFlag featureFlag;
             try
@@ -197,15 +200,28 @@ public FeatureManagementKeyValueAdapter(FeatureFilterTracing featureFilterTracin
 
                 if (telemetry.Enabled)
                 {
-                    keyValues.Add(new KeyValuePair<string, string>($"{telemetryPath}:{FeatureManagementConstants.Enabled}", telemetry.Enabled.ToString()));
-                }
+                    if (telemetry.Metadata != null)
+                    {
+                        foreach (KeyValuePair<string, string> kvp in telemetry.Metadata)
+                        {
+                            keyValues.Add(new KeyValuePair<string, string>($"{telemetryPath}:{FeatureManagementConstants.Metadata}:{kvp.Key}", kvp.Value));
+                        }
+                    }
 
-                if (telemetry.Metadata != null)
-                {
-                    foreach (KeyValuePair<string, string> kvp in telemetry.Metadata)
+                    string featureFlagId = CalculateFeatureFlagId(setting.Key, setting.Label);
+
+                    keyValues.Add(new KeyValuePair<string, string>($"{telemetryPath}:{FeatureManagementConstants.Metadata}:{FeatureManagementConstants.FeatureFlagId}", featureFlagId));
+
+                    if (endpoint != null)
                     {
-                        keyValues.Add(new KeyValuePair<string, string>($"{telemetryPath}:{FeatureManagementConstants.Metadata}:{kvp.Key}", kvp.Value));
+                        string featureFlagReference = $"{endpoint.AbsoluteUri}kv/{setting.Key}{(!string.IsNullOrWhiteSpace(setting.Label) ? $"?label={setting.Label}" : "")}";
+
+                        keyValues.Add(new KeyValuePair<string, string>($"{telemetryPath}:{FeatureManagementConstants.Metadata}:{FeatureManagementConstants.FeatureFlagReference}", featureFlagReference));
                     }
+
+                    keyValues.Add(new KeyValuePair<string, string>($"{telemetryPath}:{FeatureManagementConstants.Metadata}:{FeatureManagementConstants.ETag}", setting.ETag.ToString()));
+
+                    keyValues.Add(new KeyValuePair<string, string>($"{telemetryPath}:{FeatureManagementConstants.Enabled}", telemetry.Enabled.ToString()));
                 }
             }
 
@@ -229,5 +245,19 @@ public bool NeedsRefresh()
         {
             return false;
         }
+
+        private static string CalculateFeatureFlagId(string key, string label)
+        {
+            byte[] featureFlagIdHash;
+
+            // Convert the value consisting of key, newline character, and label to a byte array using UTF8 encoding to hash it using SHA 256
+            using (HashAlgorithm hashAlgorithm = SHA256.Create())
+            {
+                featureFlagIdHash = hashAlgorithm.ComputeHash(Encoding.UTF8.GetBytes($"{key}\n{(string.IsNullOrWhiteSpace(label) ? null : label)}"));
+            }
+
+            // Convert the hashed byte array to Base64Url
+            return featureFlagIdHash.ToBase64Url();
+        }
     }
 }

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/IConfigurationRefresher.cs

@@ -2,7 +2,6 @@
 // Licensed under the MIT license.
 //
 using Azure;
-using Microsoft.Extensions.Logging;
 using System;
 using System.Threading;
 using System.Threading.Tasks;

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/IKeyValueAdapter.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license.
 //
 using Azure.Data.AppConfiguration;
+using System;
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
@@ -10,7 +11,7 @@ namespace Microsoft.Extensions.Configuration.AzureAppConfiguration
 {
     internal interface IKeyValueAdapter
     {
-        Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Logger logger, CancellationToken cancellationToken);
+        Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Uri endpoint, Logger logger, CancellationToken cancellationToken);
 
         bool CanProcess(ConfigurationSetting setting);
 

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/JsonKeyValueAdapter.cs

@@ -22,7 +22,7 @@ internal class JsonKeyValueAdapter : IKeyValueAdapter
             KeyVaultConstants.ContentType
         };
 
-        public Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Logger logger, CancellationToken cancellationToken)
+        public Task<IEnumerable<KeyValuePair<string, string>>> ProcessKeyValue(ConfigurationSetting setting, Uri endpoint, Logger logger, CancellationToken cancellationToken)
         {
             if (setting == null)
             {

tests/Tests.AzureAppConfiguration/FeatureManagementTests.cs

@@ -6,6 +6,7 @@
 using Azure.Core.Testing;
 using Azure.Data.AppConfiguration;
 using Azure.Data.AppConfiguration.Tests;
+using Azure.Identity;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Configuration.AzureAppConfiguration;
 using Microsoft.Extensions.Configuration.AzureAppConfiguration.FeatureManagement;
@@ -14,6 +15,9 @@
 using System.Collections.Generic;
 using System.Diagnostics.Tracing;
 using System.Linq;
+using System.Net;
+using System.Security.Cryptography;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Xunit;
@@ -288,7 +292,7 @@ public class FeatureManagementTests
                         }
                     }
                     ",
-            label: default,
+            label: "label",
             contentType: FeatureManagementConstants.ContentType + ";charset=utf-8",
             eTag: new ETag("c3c231fd-39a0-4cb6-3237-4614474b92c1"));
 
@@ -1330,13 +1334,30 @@ public void WithTelemetry()
                 .AddAzureAppConfiguration(options =>
                 {
                     options.ClientManager = TestHelpers.CreateMockedConfigurationClientManager(mockClient.Object);
+                    options.Connect(TestHelpers.PrimaryConfigStoreEndpoint, new DefaultAzureCredential());
                     options.UseFeatureFlags();
                 })
                 .Build();
 
             Assert.Equal("True", config["FeatureManagement:TelemetryFeature:Telemetry:Enabled"]);
             Assert.Equal("Tag1Value", config["FeatureManagement:TelemetryFeature:Telemetry:Metadata:Tags.Tag1"]);
             Assert.Equal("Tag2Value", config["FeatureManagement:TelemetryFeature:Telemetry:Metadata:Tags.Tag2"]);
+            Assert.Equal("c3c231fd-39a0-4cb6-3237-4614474b92c1", config["FeatureManagement:TelemetryFeature:Telemetry:Metadata:ETag"]);
+
+            byte[] featureFlagIdHash;
+
+            using (HashAlgorithm hashAlgorithm = SHA256.Create())
+            {
+                featureFlagIdHash = hashAlgorithm.ComputeHash(Encoding.UTF8.GetBytes($"{FeatureManagementConstants.FeatureFlagMarker}TelemetryFeature\nlabel"));
+            }
+
+            string featureFlagId = Convert.ToBase64String(featureFlagIdHash)
+                .TrimEnd('=')
+                .Replace('+', '-')
+                .Replace('/', '_');
+
+            Assert.Equal(featureFlagId, config["FeatureManagement:TelemetryFeature:Telemetry:Metadata:FeatureFlagId"]);
+            Assert.Equal($"{TestHelpers.PrimaryConfigStoreEndpoint}kv/{FeatureManagementConstants.FeatureFlagMarker}TelemetryFeature?label=label", config["FeatureManagement:TelemetryFeature:Telemetry:Metadata:FeatureFlagReference"]);
         }
 
 

tests/Tests.AzureAppConfiguration/KeyVaultReferenceTests.cs

@@ -422,7 +422,7 @@ public void DoesNotThrowKeyVaultExceptionWhenProviderIsOptional()
             var mockKeyValueAdapter = new Mock<IKeyValueAdapter>(MockBehavior.Strict);
             mockKeyValueAdapter.Setup(adapter => adapter.CanProcess(_kv))
                 .Returns(true);
-            mockKeyValueAdapter.Setup(adapter => adapter.ProcessKeyValue(_kv, It.IsAny<Logger>(), It.IsAny<CancellationToken>()))
+            mockKeyValueAdapter.Setup(adapter => adapter.ProcessKeyValue(_kv, It.IsAny<Uri>(), It.IsAny<Logger>(), It.IsAny<CancellationToken>()))
                 .Throws(new KeyVaultReferenceException("Key vault error", null));
             mockKeyValueAdapter.Setup(adapter => adapter.InvalidateCache(null));