[Instrumentation.Hangfire] Fix 'FailedToInjectActivityContext' when no ActivityContext exists

src/OpenTelemetry.Instrumentation.Hangfire/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+* Fix 'FailedToInjectActivityContext' when no ActivityContext exists.
+  ([#2990](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/2990))
+
 ## 1.12.0-beta.1
 
 Released 2025-Jun-23

src/OpenTelemetry.Instrumentation.Hangfire/Implementation/HangfireInstrumentationJobFilterAttribute.cs

@@ -100,14 +100,13 @@ public void OnCreating(CreatingContext creatingContext)
             return;
         }
 
-        ActivityContext contextToInject = default;
-        if (Activity.Current != null)
+        if (Activity.Current == null)
         {
-            contextToInject = Activity.Current.Context;
+            return;
         }
 
         var activityContextData = new Dictionary<string, string>();
-        Propagators.DefaultTextMapPropagator.Inject(new PropagationContext(contextToInject, Baggage.Current), activityContextData, InjectActivityProperties);
+        Propagators.DefaultTextMapPropagator.Inject(new PropagationContext(Activity.Current.Context, Baggage.Current), activityContextData, InjectActivityProperties);
         creatingContext.SetJobParameter(HangfireInstrumentationConstants.ActivityContextKey, activityContextData);
     }
 

test/OpenTelemetry.Instrumentation.Hangfire.Tests/HangfireInstrumentationJobFilterAttributeTests.cs

@@ -26,6 +26,7 @@ public async Task Should_Create_Activity()
         using var tel = Sdk.CreateTracerProviderBuilder()
             .AddHangfireInstrumentation()
             .AddInMemoryExporter(exportedItems)
+            .SetSampler<AlwaysOnSampler>()
             .Build();
 
         // Act
@@ -170,6 +171,27 @@ public async Task Should_Respect_Filter_Option(string filter, bool shouldRecord)
         Assert.Equal(shouldRecord, activity.ActivityTraceFlags.HasFlag(ActivityTraceFlags.Recorded));
     }
 
+    [Fact]
+    public async Task Should_Not_Inject_Invalid_Context()
+    {
+        // Arrange
+        var exportedItems = new List<Activity>();
+        using var tel = Sdk.CreateTracerProviderBuilder()
+            .AddHangfireInstrumentation()
+            .AddInMemoryExporter(exportedItems)
+            .SetSampler<AlwaysOffSampler>()
+            .Build();
+
+        using var listener = new OpenTelemetryEventListener();
+
+        // Act
+        var jobId = BackgroundJob.Enqueue<TestJob>(x => x.Execute());
+        await this.WaitJobProcessedAsync(jobId, 5);
+
+        // Assert
+        Assert.All(listener.Messages, args => Assert.NotEqual("FailedToInjectActivityContext", args.EventName));
+    }
+
     private async Task WaitJobProcessedAsync(string jobId, int timeToWaitInSeconds)
     {
         var timeout = TimeSpan.FromSeconds(timeToWaitInSeconds);

test/OpenTelemetry.Instrumentation.Hangfire.Tests/OpenTelemetryEventListener.cs

@@ -0,0 +1,61 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using System.Diagnostics.Tracing;
+
+namespace OpenTelemetry.Instrumentation.Hangfire.Tests;
+
+internal class OpenTelemetryEventListener : EventListener
+{
+    private const string EventSourceName = "OpenTelemetry-Api";
+
+    private readonly Queue<EventWrittenEventArgs> events = new();
+    private readonly AutoResetEvent eventWritten = new(false);
+    private EventSource? apiEventSource;
+
+    public IEnumerable<EventWrittenEventArgs> Messages
+    {
+        get
+        {
+            if (this.events.Count == 0)
+            {
+                this.eventWritten.WaitOne(TimeSpan.FromSeconds(3));
+            }
+
+            while (this.events.Count != 0)
+            {
+                yield return this.events.Dequeue();
+            }
+        }
+    }
+
+    public override void Dispose()
+    {
+        if (this.apiEventSource != null)
+        {
+            this.DisableEvents(this.apiEventSource);
+        }
+
+        base.Dispose();
+    }
+
+    protected override void OnEventSourceCreated(EventSource eventSource)
+    {
+        if (eventSource.Name == EventSourceName)
+        {
+            this.apiEventSource = eventSource;
+            this.EnableEvents(eventSource, EventLevel.Verbose, EventKeywords.All);
+        }
+
+        base.OnEventSourceCreated(eventSource);
+    }
+
+    protected override void OnEventWritten(EventWrittenEventArgs eventData)
+    {
+        if (eventData.EventSource.Name == EventSourceName)
+        {
+            this.events.Enqueue(eventData);
+            this.eventWritten.Set();
+        }
+    }
+}