Add long running activity tag for SignalR connections

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionDispatcher.cs

@@ -115,6 +115,9 @@ public async Task ExecuteNegotiateAsync(HttpContext context, HttpConnectionDispa
 
         private async Task ExecuteAsync(HttpContext context, ConnectionDelegate connectionDelegate, HttpConnectionDispatcherOptions options, ConnectionLogScope logScope)
         {
+            // set a tag to allow Application Performance Management tools to differentiate long running requests for reporting purposes
+            context.Features.Get<IHttpActivityFeature>()?.Activity.AddTag("http.long_running", "true");
+
             var supportedTransports = options.Transports;
 
             // Server sent events transport

src/SignalR/common/Http.Connections/test/HttpConnectionDispatcherTests.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Buffers;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.IO.Pipelines;
 using System.Linq;
@@ -2078,7 +2079,7 @@ public async Task WriteThatIsDisposedBeforeCompleteReturns404()
                     TransportMaxBufferSize = 13,
                     ApplicationMaxBufferSize = 13
                 };
-                
+
                 var connection = manager.CreateConnection(options);
                 connection.TransportType = HttpTransportType.LongPolling;
 
@@ -2594,6 +2595,53 @@ public async Task DisposeLongPollingConnectionDisposesServiceScope()
             }
         }
 
+        private class TestActivityFeature : IHttpActivityFeature
+        {
+            public TestActivityFeature(Activity activity)
+            {
+                Activity = activity;
+            }
+
+            public Activity Activity { get; set; }
+        }
+
+        [Fact]
+        public async Task LongRunningActivityTagSetOnExecuteAsync()
+        {
+            using (StartVerifiableLog())
+            {
+                var manager = CreateConnectionManager(LoggerFactory);
+                var connection = manager.CreateConnection();
+                connection.TransportType = HttpTransportType.ServerSentEvents;
+
+                var dispatcher = new HttpConnectionDispatcher(manager, LoggerFactory);
+                var services = new ServiceCollection();
+                services.AddSingleton<NeverEndingConnectionHandler>();
+                var context = MakeRequest("/foo", connection, services);
+                var cts = new CancellationTokenSource();
+                context.RequestAborted = cts.Token;
+                SetTransport(context, HttpTransportType.ServerSentEvents);
+
+                var builder = new ConnectionBuilder(services.BuildServiceProvider());
+                builder.UseConnectionHandler<NeverEndingConnectionHandler>();
+                var app = builder.Build();
+
+                var activityFeature = new TestActivityFeature(new Activity("name"));
+                activityFeature.Activity.Start();
+                context.Features.Set<IHttpActivityFeature>(activityFeature);
+
+                _ = dispatcher.ExecuteAsync(context, new HttpConnectionDispatcherOptions(), app);
+
+                Assert.Equal("true", Activity.Current.GetTagItem("http.long_running"));
+
+                connection.Transport.Output.Complete();
+
+                await connection.ConnectionClosed.WaitForCancellationAsync().DefaultTimeout();
+
+                activityFeature.Activity.Dispose();
+            }
+        }
+
         private static async Task CheckTransportSupported(HttpTransportType supportedTransports, HttpTransportType transportType, int status, ILoggerFactory loggerFactory)
         {
             var manager = CreateConnectionManager(loggerFactory);