feat: Add support for w3c trace parent headers for outgoing requests

src/Sentry/Extensibility/DisabledHub.cs

@@ -99,6 +99,11 @@ public void BindException(Exception exception, ISpan span)
     /// </summary>
     public BaggageHeader? GetBaggage() => null;
 
+    /// <summary>
+    /// Returns null.
+    /// </summary>
+    public W3CTraceparentHeader? GetTraceparentHeader() => null;
+
     /// <summary>
     /// Returns sampled out transaction context.
     /// </summary>

src/Sentry/Extensibility/HubAdapter.cs

@@ -140,6 +140,13 @@ public void BindException(Exception exception, ISpan span) =>
     public BaggageHeader? GetBaggage()
         => SentrySdk.GetBaggage();
 
+    /// <summary>
+    /// Forwards the call to <see cref="SentrySdk"/>.
+    /// </summary>
+    [DebuggerStepThrough]
+    public W3CTraceparentHeader? GetTraceparentHeader()
+        => SentrySdk.GetTraceparentHeader();
+
     /// <summary>
     /// Forwards the call to <see cref="SentrySdk"/>.
     /// </summary>

src/Sentry/IHub.cs

@@ -59,6 +59,11 @@ public ITransactionTracer StartTransaction(
     /// </summary>
     public BaggageHeader? GetBaggage();
 
+    /// <summary>
+    /// Gets the W3C Trace Context traceparent header that allows tracing across services
+    /// </summary>
+    public W3CTraceparentHeader? GetTraceparentHeader();
+
     /// <summary>
     /// Continues a trace based on HTTP header values provided as strings.
     /// </summary>

src/Sentry/Internal/Hub.cs

@@ -314,6 +314,18 @@ public BaggageHeader GetBaggage()
         return propagationContext.GetOrCreateDynamicSamplingContext(_options, _replaySession).ToBaggageHeader();
     }
 
+    public W3CTraceparentHeader? GetTraceparentHeader()
+    {
+        if (GetSpan()?.GetTraceHeader() is { } traceHeader)
+        {
+            return new W3CTraceparentHeader(traceHeader.TraceId, traceHeader.SpanId, traceHeader.IsSampled);
+        }
+
+        // We fall back to the propagation context
+        var propagationContext = CurrentScope.PropagationContext;
+        return new W3CTraceparentHeader(propagationContext.TraceId, propagationContext.SpanId, null);
+    }
+
     public TransactionContext ContinueTrace(
         string? traceHeader,
         string? baggageHeader,

src/Sentry/SentryMessageHandler.cs

@@ -137,6 +137,10 @@ private void PropagateTraceHeaders(HttpRequestMessage request, string url, ISpan
         {
             AddSentryTraceHeader(request, parentSpan);
             AddBaggageHeader(request);
+            if (_options?.PropagateTraceparent is true)
+            {
+                AddTraceparentHeader(request, parentSpan);
+            }
         }
     }
 
@@ -181,4 +185,16 @@ private void AddBaggageHeader(HttpRequestMessage request)
         // Set the baggage header
         request.Headers.Add(BaggageHeader.HttpHeaderName, baggage.ToString());
     }
+
+    private void AddTraceparentHeader(HttpRequestMessage request, ISpan? parentSpan)
+    {
+        // Set W3C traceparent header if it hasn't already been set
+        if (!request.Headers.Contains(W3CTraceparentHeader.HttpHeaderName) &&
+            // Use the span created by this integration as parent, instead of its own parent
+            (parentSpan?.GetTraceHeader() ?? _hub.GetTraceHeader()) is { } traceHeader)
+        {
+            var traceparentHeader = new W3CTraceparentHeader(traceHeader.TraceId, traceHeader.SpanId, traceHeader.IsSampled);
+            request.Headers.Add(W3CTraceparentHeader.HttpHeaderName, traceparentHeader.ToString());
+        }
+    }
 }

src/Sentry/SentryOptions.cs

@@ -995,6 +995,18 @@ public IList<StringOrRegex> TracePropagationTargets
         set => _tracePropagationTargets = value.WithConfigBinding();
     }
 
+    /// <summary>
+    /// Whether to send W3C Trace Context traceparent headers in outgoing HTTP requests for distributed tracing.
+    /// When enabled, the SDK will send the <c>traceparent</c> header in addition to the <c>sentry-trace</c> header
+    /// for requests matching <see cref="TracePropagationTargets"/>.
+    /// </summary>
+    /// <remarks>
+    /// The default value is <c>false</c>. Set to <c>true</c> to enable W3C Trace Context propagation
+    /// for interoperability with services that support OpenTelemetry standards.
+    /// </remarks>
+    /// <seealso href="https://develop.sentry.dev/sdk/telemetry/traces/#propagatetraceparent"/>
+    public bool PropagateTraceparent { get; set; } = false;
+
     internal ITransactionProfilerFactory? TransactionProfilerFactory { get; set; }
 
     private StackTraceMode? _stackTraceMode;

src/Sentry/SentrySdk.cs

@@ -716,6 +716,13 @@ public static void BindException(Exception exception, ISpan span)
     public static BaggageHeader? GetBaggage()
         => CurrentHub.GetBaggage();
 
+    /// <summary>
+    /// Gets the W3C Trace Context traceparent header that allows tracing across services
+    /// </summary>
+    [DebuggerStepThrough]
+    public static W3CTraceparentHeader? GetTraceparentHeader()
+        => CurrentHub.GetTraceparentHeader();
+
     /// <summary>
     /// Continues a trace based on HTTP header values provided as strings.
     /// </summary>

src/Sentry/W3CTraceparentHeader.cs

@@ -0,0 +1,39 @@
+namespace Sentry;
+
+/// <summary>
+/// W3C Trace Context traceparent header.
+/// </summary>
+public class W3CTraceparentHeader
+{
+    internal const string HttpHeaderName = "traceparent";
+
+    /// <summary>
+    /// Trace ID.
+    /// </summary>
+    public SentryId TraceId { get; }
+
+    /// <summary>
+    /// Span ID.
+    /// </summary>
+    public SpanId SpanId { get; }
+
+    /// <summary>
+    /// Whether the trace is sampled.
+    /// </summary>
+    public bool? IsSampled { get; }
+
+    /// <summary>
+    /// Initializes an instance of <see cref="W3CTraceparentHeader"/>.
+    /// </summary>
+    public W3CTraceparentHeader(SentryId traceId, SpanId spanId, bool? isSampled)
+    {
+        TraceId = traceId;
+        SpanId = spanId;
+        IsSampled = isSampled;
+    }
+
+    /// <inheritdoc />
+    public override string ToString() => IsSampled is { } isSampled
+        ? $"00-{TraceId}-{SpanId}-{(isSampled ? "01" : "00")}"
+        : $"00-{TraceId}-{SpanId}-00";
+}

test/Sentry.Tests/ApiApprovalTests.Run.DotNet8_0.verified.txt

@@ -198,6 +198,7 @@ namespace Sentry
         Sentry.BaggageHeader? GetBaggage();
         Sentry.ISpan? GetSpan();
         Sentry.SentryTraceHeader? GetTraceHeader();
+        Sentry.W3CTraceparentHeader? GetTraceparentHeader();
         void PauseSession();
         void ResumeSession();
         void StartSession();
@@ -718,6 +719,7 @@ namespace Sentry
         public int MaxQueueItems { get; set; }
         public Sentry.Extensibility.INetworkStatusListener? NetworkStatusListener { get; set; }
         public double? ProfilesSampleRate { get; set; }
+        public bool PropagateTraceparent { get; set; }
         public string? Release { get; set; }
         public Sentry.ReportAssembliesMode ReportAssembliesMode { get; set; }
         public bool RequestBodyCompressionBuffered { get; set; }
@@ -864,6 +866,7 @@ namespace Sentry
         public static Sentry.BaggageHeader? GetBaggage() { }
         public static Sentry.ISpan? GetSpan() { }
         public static Sentry.SentryTraceHeader? GetTraceHeader() { }
+        public static Sentry.W3CTraceparentHeader? GetTraceparentHeader() { }
         public static Sentry.ITransactionTracer? GetTransaction() { }
         public static System.IDisposable Init() { }
         public static System.IDisposable Init(Sentry.SentryOptions options) { }
@@ -1298,6 +1301,14 @@ namespace Sentry
         protected abstract void WriteAdditionalProperties(System.Text.Json.Utf8JsonWriter writer, Sentry.Extensibility.IDiagnosticLogger? logger);
         public void WriteTo(System.Text.Json.Utf8JsonWriter writer, Sentry.Extensibility.IDiagnosticLogger? logger) { }
     }
+    public class W3CTraceparentHeader
+    {
+        public W3CTraceparentHeader(Sentry.SentryId traceId, Sentry.SpanId spanId, bool? isSampled) { }
+        public bool? IsSampled { get; }
+        public Sentry.SpanId SpanId { get; }
+        public Sentry.SentryId TraceId { get; }
+        public override string ToString() { }
+    }
 }
 namespace Sentry.Ben.BlockingDetector
 {
@@ -1384,6 +1395,7 @@ namespace Sentry.Extensibility
         public Sentry.BaggageHeader? GetBaggage() { }
         public Sentry.ISpan? GetSpan() { }
         public Sentry.SentryTraceHeader? GetTraceHeader() { }
+        public Sentry.W3CTraceparentHeader? GetTraceparentHeader() { }
         public void PauseSession() { }
         public System.IDisposable PushScope() { }
         public System.IDisposable PushScope<TState>(TState state) { }
@@ -1433,6 +1445,7 @@ namespace Sentry.Extensibility
         public Sentry.BaggageHeader? GetBaggage() { }
         public Sentry.ISpan? GetSpan() { }
         public Sentry.SentryTraceHeader? GetTraceHeader() { }
+        public Sentry.W3CTraceparentHeader? GetTraceparentHeader() { }
         public void PauseSession() { }
         public System.IDisposable PushScope() { }
         public System.IDisposable PushScope<TState>(TState state) { }

test/Sentry.Tests/HubTests.cs

@@ -1363,6 +1363,47 @@ public void GetBaggage_NoSpanActive_ReturnsBaggageFromPropagationContext()
         Assert.Contains("sentry-trace_id=43365712692146d08ee11a729dfbcaca", baggage!.ToString());
     }
 
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void GetTraceparentHeader_ReturnsHeaderForActiveSpan(bool isSampled)
+    {
+        // Arrange
+        _fixture.Options.TracesSampleRate = isSampled ? 1 : 0;
+        var hub = _fixture.GetSut();
+        var transaction = hub.StartTransaction("foo", "bar");
+        hub.ConfigureScope(scope => scope.Transaction = transaction);
+
+        // Act
+        var header = hub.GetTraceparentHeader();
+
+        // Assert
+        header.Should().NotBeNull();
+        header.SpanId.Should().Be(transaction.SpanId);
+        header.TraceId.Should().Be(transaction.TraceId);
+        header.IsSampled.Should().Be(transaction.IsSampled);
+    }
+
+    [Fact]
+    public void GetTraceparentHeader_NoSpanActive_ReturnsHeaderFromPropagationContext()
+    {
+        // Arrange
+        var hub = _fixture.GetSut();
+        var propagationContext = new SentryPropagationContext(
+            SentryId.Parse("75302ac48a024bde9a3b3734a82e36c8"),
+            SpanId.Parse("2000000000000000"));
+        hub.ConfigureScope(scope => scope.SetPropagationContext(propagationContext));
+
+        // Act
+        var header = hub.GetTraceparentHeader();
+
+        // Assert
+        header.Should().NotBeNull();
+        header.SpanId.Should().Be(propagationContext.SpanId);
+        header.TraceId.Should().Be(propagationContext.TraceId);
+        header.IsSampled.Should().BeNull();
+    }
+
     [Fact]
     public void ContinueTrace_ReceivesHeaders_SetsPropagationContextAndReturnsTransactionContext()
     {

test/Sentry.Tests/Protocol/W3CTraceparentHeaderTests.cs

@@ -0,0 +1,73 @@
+namespace Sentry.Tests.Protocol;
+
+public class W3CTraceparentHeaderTests
+{
+    [Fact]
+    public void ToString_WithSampledTrue_Works()
+    {
+        // Arrange
+        var traceId = SentryId.Parse("75302ac48a024bde9a3b3734a82e36c8");
+        var spanId = SpanId.Parse("1000000000000000");
+        var header = new W3CTraceparentHeader(traceId, spanId, true);
+
+        // Act
+        var result = header.ToString();
+
+        // Assert
+        result.Should().Be("00-75302ac48a024bde9a3b3734a82e36c8-1000000000000000-01");
+    }
+
+    [Fact]
+    public void ToString_WithSampledFalse_Works()
+    {
+        // Arrange
+        var traceId = SentryId.Parse("75302ac48a024bde9a3b3734a82e36c8");
+        var spanId = SpanId.Parse("1000000000000000");
+        var header = new W3CTraceparentHeader(traceId, spanId, false);
+
+        // Act
+        var result = header.ToString();
+
+        // Assert
+        result.Should().Be("00-75302ac48a024bde9a3b3734a82e36c8-1000000000000000-00");
+    }
+
+    [Fact]
+    public void ToString_WithoutSampled_DefaultsToFalse()
+    {
+        // Arrange
+        var traceId = SentryId.Parse("75302ac48a024bde9a3b3734a82e36c8");
+        var spanId = SpanId.Parse("1000000000000000");
+        var header = new W3CTraceparentHeader(traceId, spanId, null);
+
+        // Act
+        var result = header.ToString();
+
+        // Assert
+        result.Should().Be("00-75302ac48a024bde9a3b3734a82e36c8-1000000000000000-00");
+    }
+
+    [Fact]
+    public void Constructor_StoresProperties()
+    {
+        // Arrange
+        var traceId = SentryId.Parse("75302ac48a024bde9a3b3734a82e36c8");
+        var spanId = SpanId.Parse("1000000000000000");
+        var isSampled = true;
+
+        // Act
+        var header = new W3CTraceparentHeader(traceId, spanId, isSampled);
+
+        // Assert
+        header.TraceId.Should().Be(traceId);
+        header.SpanId.Should().Be(spanId);
+        header.IsSampled.Should().Be(isSampled);
+    }
+
+    [Fact]
+    public void HttpHeaderName_IsCorrect()
+    {
+        // Act & Assert
+        W3CTraceparentHeader.HttpHeaderName.Should().Be("traceparent");
+    }
+}