WN Update: SignalR ActivitySource

Author: wadepickett

aspnetcore/release-notes/aspnetcore-9.0.md

@@ -4,7 +4,7 @@ author: rick-anderson
 description: Learn about the new features in ASP.NET Core 9.0.
 ms.author: riande
 ms.custom: mvc
-ms.date: 10/07/2024
+ms.date: 11/19/2024
 uid: aspnetcore-9
 ---
 # What's new in ASP.NET Core 9.0

aspnetcore/release-notes/aspnetcore-9/includes/signalr-distributed-tracing-improvements.md

@@ -1,6 +1,10 @@
 ### Improved Activities for SignalR
 
-SignalR now has an ActivitySource named `Microsoft.AspNetCore.SignalR.Server` that emits events for hub method calls:
+SignalR now has an ActivitySource for both the hub server and client.
+
+#### .NET SignalR server ActivitySource
+
+The SignalR ActivitySource named `Microsoft.AspNetCore.SignalR.Server` emits events for hub method calls:
 
 * Every method is its own activity, so anything that emits an activity during the hub method call is under the hub method activity.
 * Hub method activities don't have a parent. This means they are not bundled under the long-running SignalR connection.
@@ -15,29 +19,19 @@ The following example uses the [.NET Aspire dashboard](/dotnet/aspire/fundamenta
 
 Add the following startup code to the `Program.cs` file:
 
-```csharp
-// Set OTEL_EXPORTER_OTLP_ENDPOINT environment variable depending on where your OTEL endpoint is
-var builder = WebApplication.CreateBuilder(args);
+[!code-csharp[](~/release-notes/aspnetcore-9/samples/SignalRChatTraceExample/Program.cs?name=snippet_trace_signalr_server&highlight=1,13-26)]
+
+The following is example output from the Aspire Dashboard:
 
-builder.Services.AddRazorPages();
-builder.Services.AddSignalR();
+:::image type="content" source="~/release-notes/aspnetcore-9/_static/signalr-activities-events.png" alt-text="Activity list for SignalR Hub method call events":::
 
-builder.Services.AddOpenTelemetry()
-    .WithTracing(tracing =>
-    {
-        if (builder.Environment.IsDevelopment())
-        {
-            // We want to view all traces in development
-            tracing.SetSampler(new AlwaysOnSampler());
-        }
+#### .NET SignalR client ActivitySource
 
-        tracing.AddAspNetCoreInstrumentation();
-        tracing.AddSource("Microsoft.AspNetCore.SignalR.Server");
-    });
+The SignalR ActivitySource named "Microsoft.AspNetCore.SignalR.Client" emits events for a SignalR client:
 
-builder.Services.ConfigureOpenTelemetryTracerProvider(tracing => tracing.AddOtlpExporter());
-```
+* .NET SignalR client has an `ActivitySource` named "Microsoft.AspNetCore.SignalR.Client". Hub invocations now create a client span. Note that other SignalR clients, such as the JavaScript client, don't support tracing. This feature will be added to more clients in future releases.
+* Hub invocations on the client and server support [context propagation](https://opentelemetry.io/docs/concepts/context-propagation/). Propagating the trace context enables true distributed tracing. It's now possible to see invocations flow from the client to the server and back.
 
-The following is example output from the Aspire Dashboard:
+Here's how these new activities look in the [.NET Aspire dashboard](https://learn.microsoft.com/dotnet/aspire/fundamentals/dashboard/overview?tabs=bash#standalone-mode):
 
-:::image type="content" source="~/release-notes/aspnetcore-9/_static/signalr-activites-events.png" alt-text="Activity list for SignalR Hub method call events":::
+![SignalR distributed tracing in Aspire dashboard](~/release-notes/aspnetcore-9/_static/signalr-distributed-tracing-aspire-dashboard.png)