Detect SignalR usage for request tracing (#570)

* collect usage of SignalR

* fix typo

* fix typo

* rename signalR

Author: zhiyuanliang-ms

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

@@ -26,7 +26,7 @@ internal class AzureAppConfigurationProvider : ConfigurationProvider, IConfigura
     {
         private bool _optional;
         private bool _isInitialLoadComplete = false;
-        private bool _isFeatureManagementVersionInspected;
+        private bool _isAssemblyInspected;
         private readonly bool _requestTracingEnabled;
         private readonly IConfigurationClientManager _configClientManager;
         private AzureAppConfigurationOptions _options;
@@ -189,7 +189,7 @@ public async Task RefreshAsync(CancellationToken cancellationToken)
                 try
                 {
                     // FeatureManagement assemblies may not be loaded on provider startup, so version information is gathered upon first refresh for tracing
-                    EnsureFeatureManagementVersionInspected();
+                    EnsureAssemblyInspected();
 
                     var utcNow = DateTimeOffset.UtcNow;
                     IEnumerable<KeyValueWatcher> cacheExpiredWatchers = _options.ChangeWatchers.Where(changeWatcher => utcNow >= changeWatcher.CacheExpires);
@@ -1186,17 +1186,22 @@ private IEnumerable<ConfigurationSetting> GetCurrentKeyValueCollection(string ke
             return currentKeyValues;
         }
 
-        private void EnsureFeatureManagementVersionInspected()
+        private void EnsureAssemblyInspected()
         {
-            if (!_isFeatureManagementVersionInspected)
+            if (!_isAssemblyInspected)
             {
-                _isFeatureManagementVersionInspected = true;
+                _isAssemblyInspected = true;
 
                 if (_requestTracingEnabled && _requestTracingOptions != null)
                 {
                     _requestTracingOptions.FeatureManagementVersion = TracingUtils.GetAssemblyVersion(RequestTracingConstants.FeatureManagementAssemblyName);
 
                     _requestTracingOptions.FeatureManagementAspNetCoreVersion = TracingUtils.GetAssemblyVersion(RequestTracingConstants.FeatureManagementAspNetCoreAssemblyName);
+
+                    if (TracingUtils.GetAssemblyVersion(RequestTracingConstants.SignalRAssemblyName) != null)
+                    {
+                        _requestTracingOptions.IsSignalRUsed = true;
+                    }
                 }
             }
         }

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Constants/RequestTracingConstants.cs

@@ -30,12 +30,15 @@ internal class RequestTracingConstants
         public const string KeyVaultConfiguredTag = "UsesKeyVault";
         public const string KeyVaultRefreshConfiguredTag = "RefreshesKeyVault";
         public const string ReplicaCountKey = "ReplicaCount";
+        public const string SignalRUsedTag = "UsesSignalR";
 
         public const string DiagnosticHeaderActivityName = "Azure.CustomDiagnosticHeaders";
         public const string CorrelationContextHeader = "Correlation-Context";
         public const string UserAgentHeader = "User-Agent";
 
         public const string FeatureManagementAssemblyName = "Microsoft.FeatureManagement";
         public const string FeatureManagementAspNetCoreAssemblyName = "Microsoft.FeatureManagement.AspNetCore";
+
+        public const string SignalRAssemblyName = "Microsoft.AspNetCore.SignalR";
     }
 }

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

@@ -46,5 +46,10 @@ internal class RequestTracingOptions
         /// Version of the Microsoft.FeatureManagement.AspNetCore assembly, if present in the application.
         /// </summary>
         public string FeatureManagementAspNetCoreVersion { get; set; }
+
+        /// <summary>
+        /// Flag to indicate whether Microsoft.AspNetCore.SignalR assembly is present in the application.
+        /// </summary>
+        public bool IsSignalRUsed { get; set; } = false;
     }
 }

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

@@ -160,6 +160,11 @@ private static string CreateCorrelationContextHeader(RequestType requestType, Re
                 correlationContextTags.Add(RequestTracingConstants.KeyVaultRefreshConfiguredTag);
             }
 
+            if (requestTracingOptions.IsSignalRUsed)
+            {
+                correlationContextTags.Add(RequestTracingConstants.SignalRUsedTag);
+            }
+
             var sb = new StringBuilder();
 
             foreach (KeyValuePair<string,string> kvp in correlationContextKeyValues)