fix: http integration uses correct parent span id (#4264)

Author: bruno-garcia

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Fixes
+
+- The HTTP instrumentation uses the span created for the outgoing request in the sentry-trace header, fixing the parent-child relationship between client and server ([#4264](https://github.com/getsentry/sentry-dotnet/pull/4264))
+
 ### Dependencies
 
 - Bump Native SDK from v0.8.5 to v0.9.0 ([#4260](https://github.com/getsentry/sentry-dotnet/pull/4260))

Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
 
   <PropertyGroup>
-    <VersionPrefix>5.10.0</VersionPrefix>
+    <VersionPrefix>5.11.0-alpha.1</VersionPrefix>
     <LangVersion>13</LangVersion>
     <AccelerateBuildsInVisualStudio>true</AccelerateBuildsInVisualStudio>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>

src/Sentry/SentryMessageHandler.cs

@@ -86,7 +86,7 @@ protected override async Task<HttpResponseMessage> SendAsync(
         var span = ProcessRequest(request, method, url);
         try
         {
-            PropagateTraceHeaders(request, url);
+            PropagateTraceHeaders(request, url, span);
             var response = await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
             HandleResponse(response, span, method, url);
             return response;
@@ -108,7 +108,7 @@ protected override HttpResponseMessage Send(HttpRequestMessage request, Cancella
         var span = ProcessRequest(request, method, url);
         try
         {
-            PropagateTraceHeaders(request, url);
+            PropagateTraceHeaders(request, url, span);
             var response = base.Send(request, cancellationToken);
             HandleResponse(response, span, method, url);
             return response;
@@ -121,7 +121,7 @@ protected override HttpResponseMessage Send(HttpRequestMessage request, Cancella
     }
 #endif
 
-    private void PropagateTraceHeaders(HttpRequestMessage request, string url)
+    private void PropagateTraceHeaders(HttpRequestMessage request, string url, ISpan? parentSpan)
     {
         // Assign a default inner handler for convenience the first time this is used.
         // We can't do this in a constructor, or it will throw when used with HttpMessageHandlerBuilderFilter.
@@ -135,15 +135,17 @@ private void PropagateTraceHeaders(HttpRequestMessage request, string url)
 
         if (_options?.TracePropagationTargets.MatchesSubstringOrRegex(url) is true or null)
         {
-            AddSentryTraceHeader(request);
+            AddSentryTraceHeader(request, parentSpan);
             AddBaggageHeader(request);
         }
     }
 
-    private void AddSentryTraceHeader(HttpRequestMessage request)
+    private void AddSentryTraceHeader(HttpRequestMessage request, ISpan? parentSpan)
     {
         // Set trace header if it hasn't already been set
-        if (!request.Headers.Contains(SentryTraceHeader.HttpHeaderName) && _hub.GetTraceHeader() is { } traceHeader)
+        if (!request.Headers.Contains(SentryTraceHeader.HttpHeaderName) &&
+            // Use the span created by this integration as parent, instead of its own parent
+            (parentSpan?.GetTraceHeader() ?? _hub.GetTraceHeader()) is { } traceHeader)
         {
             request.Headers.Add(SentryTraceHeader.HttpHeaderName, traceHeader.ToString());
         }

test/Sentry.Tests/SentryHttpMessageHandlerTests.cs

@@ -33,6 +33,40 @@ public async Task SendAsync_SentryTraceHeaderNotSet_SetsHeader_ByDefault()
             string.Concat(h.Value) == "75302ac48a024bde9a3b3734a82e36c8-1000000000000000-0");
     }
 
+    [Fact]
+    public async Task SendAsync_SentryTraceHeaderNotSet_SetsHeader_ToCorrectParent()
+    {
+        // Arrange
+        var hub = Substitute.For<IHub>();
+
+        const string rootTraceHeader = "75302ac48a024bde9a3b3734a82e36c8-1000000000000000-1";
+        hub.GetTraceHeader().ReturnsForAnyArgs(
+            SentryTraceHeader.Parse(rootTraceHeader));
+        var parentSpan = Substitute.For<ISpan>();
+        parentSpan.GetTraceHeader().ReturnsForAnyArgs(
+            SentryTraceHeader.Parse(rootTraceHeader));
+        hub.GetSpan().ReturnsForAnyArgs(parentSpan);
+        const string httpSpanTraceHeader = "75302ac48a024bde9a3b3734a82e36c8-2000000000000000-1";
+        var httpSpan = Substitute.For<ISpan>();
+        httpSpan.GetTraceHeader().ReturnsForAnyArgs(
+            SentryTraceHeader.Parse(httpSpanTraceHeader));
+        parentSpan.StartChild(Arg.Any<string>()).ReturnsForAnyArgs(httpSpan);
+
+        using var innerHandler = new RecordingHttpMessageHandler(new FakeHttpMessageHandler());
+        using var sentryHandler = new SentryHttpMessageHandler(innerHandler, hub);
+        using var client = new HttpClient(sentryHandler);
+
+        // Act
+        await client.GetAsync("https://localhost/");
+
+        using var request = innerHandler.GetRequests().Single();
+
+        // Assert
+        request.Headers.Should().Contain(h =>
+            h.Key == "sentry-trace" &&
+            string.Concat(h.Value) == httpSpanTraceHeader);
+    }
+
     [Fact]
     public async Task SendAsync_SentryTraceHeaderNotSet_SetsHeader_WhenUrlMatchesPropagationOptions()
     {