[Instrumentation.AspNet] Baggage is propagated before the Activity is created (#3820)

Co-authored-by: Rajkumar Rangaraj <rajrang@microsoft.com>

Author: Kielek

src/OpenTelemetry.Instrumentation.AspNet.TelemetryHttpModule/ActivityHelper.cs

@@ -60,6 +60,7 @@ public static bool HasStarted(HttpContextBase context, out Activity? aspNetActiv
         Activity? activity = null;
         try
         {
+            Baggage.Current = propagationContext.Baggage;
             activity = onRequestStartedCallback?.Invoke(context, propagationContext.ActivityContext);
         }
         catch (Exception callbackEx)
@@ -71,8 +72,6 @@ public static bool HasStarted(HttpContextBase context, out Activity? aspNetActiv
         {
             if (textMapPropagator is not TraceContextPropagator)
             {
-                Baggage.Current = propagationContext.Baggage;
-
                 context.Items[ContextKey] = new ContextHolder(activity, RuntimeContext.GetValue(BaggageSlotName));
             }
             else

src/OpenTelemetry.Instrumentation.AspNet.TelemetryHttpModule/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+* Propagate baggage before `Activity` is created.
+  ([#3820](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/3820))
+
 ## 1.15.0
 
 Released 2026-Jan-21

test/OpenTelemetry.Instrumentation.AspNet.TelemetryHttpModule.Tests/ActivityHelperTest.cs

@@ -1,8 +1,6 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-using System.Collections;
-using System.Collections.Specialized;
 using System.Diagnostics;
 using System.Web;
 using OpenTelemetry.Context.Propagation;
@@ -56,6 +54,16 @@ public void Has_Started_Returns_Correctly()
         Assert.Equal(activity, aspNetActivity);
     }
 
+    [Fact]
+    public void Baggage_Is_Restored_Before_Starting_Activity()
+    {
+        this.EnableListener();
+        var propagator = new MockTextMapPropagator();
+        var context = HttpContextHelper.GetFakeHttpContextBase();
+        using var activity = ActivityHelper.StartAspNetActivity(propagator, context, this.StartTestActivityWithBaggageAttribute);
+        Assert.Equal(MockTextMapPropagator.BaggageValue, activity?.Tags.FirstOrDefault(kv => kv.Key == MockTextMapPropagator.BaggageKey).Value);
+    }
+
     [Fact]
     public async Task Can_Restore_Activity()
     {
@@ -507,72 +515,45 @@ private void EnableListener(Action<Activity>? onStarted = null, Action<Activity>
         return this.testActivitySource.StartActivity(ActivityKind.Server, activityContext);
     }
 
-    private class TestHttpRequest : HttpRequestBase
+    private Activity? StartTestActivityWithBaggageAttribute(HttpContextBase httpContext, ActivityContext activityContext)
     {
-        private readonly NameValueCollection headers = [];
-
-        public override NameValueCollection Headers => this.headers;
-
-        public override UnvalidatedRequestValuesBase Unvalidated => new TestUnvalidatedRequestValues(this.headers);
+        var baggageValue = Baggage.Current.GetBaggage(MockTextMapPropagator.BaggageKey);
+        var activity = this.testActivitySource.StartActivity(ActivityKind.Server, activityContext);
+        activity?.AddTag(MockTextMapPropagator.BaggageKey, baggageValue);
+        return activity;
     }
 
-    private class TestUnvalidatedRequestValues : UnvalidatedRequestValuesBase
-    {
-        public TestUnvalidatedRequestValues(NameValueCollection headers)
-        {
-            this.Headers = headers;
-        }
-
-        public override NameValueCollection Headers { get; }
-    }
-
-    private class TestHttpResponse : HttpResponseBase
-    {
-    }
-
-    private class TestHttpServerUtility : HttpServerUtilityBase
+    private class NoopTextMapPropagator : TextMapPropagator
     {
-        private readonly HttpContextBase context;
+        public override ISet<string>? Fields => null;
 
-        public TestHttpServerUtility(HttpContextBase context)
+        public override PropagationContext Extract<T>(PropagationContext context, T carrier, Func<T, string, IEnumerable<string>?> getter)
         {
-            this.context = context;
+            return default;
         }
 
-        public override Exception GetLastError()
+        public override void Inject<T>(PropagationContext context, T carrier, Action<T, string, string> setter)
         {
-            return this.context.Error;
         }
     }
 
-    private class TestHttpContext : HttpContextBase
+    private class MockTextMapPropagator : TextMapPropagator
     {
-        private readonly Hashtable items;
-
-        public TestHttpContext(Exception? error = null)
-        {
-            this.Server = new TestHttpServerUtility(this);
-            this.items = [];
-            this.Error = error;
-        }
-
-        public override HttpRequestBase Request { get; } = new TestHttpRequest();
-
-        /// <inheritdoc />
-        public override IDictionary Items => this.items;
-
-        public override Exception? Error { get; }
+        internal const string BaggageKey = "TestKey1";
+        internal const string BaggageValue = "TestValue1";
 
-        public override HttpServerUtilityBase Server { get; }
-    }
-
-    private class NoopTextMapPropagator : TextMapPropagator
-    {
         public override ISet<string>? Fields => null;
 
         public override PropagationContext Extract<T>(PropagationContext context, T carrier, Func<T, string, IEnumerable<string>?> getter)
         {
-            return default;
+            var baggage = Baggage.Create(new Dictionary<string, string>
+            {
+                { BaggageKey, BaggageValue },
+            });
+
+            var activityContext = new ActivityContext(ActivityTraceId.CreateRandom(), ActivitySpanId.CreateRandom(), ActivityTraceFlags.Recorded);
+
+            return new PropagationContext(activityContext, baggage);
         }
 
         public override void Inject<T>(PropagationContext context, T carrier, Action<T, string, string> setter)