OcelotMessageInvokerPoolIntegration.cs

// <copyright file="OcelotMessageInvokerPoolIntegration.cs" company="Datadog">
// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2 License.
// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2017 Datadog, Inc.
// </copyright>
#nullable enable

#if NET6_0_OR_GREATER

using System;
using System.ComponentModel;
using Datadog.Trace.ClrProfiler.CallTarget;
using Datadog.Trace.Configuration;

namespace Datadog.Trace.ClrProfiler.AutoInstrumentation.Http.HttpClient.SocketsHttpHandler;

/// <summary>
/// Ocelot.Requester.MessageInvokerPool::CreateHandler calltarget instrumentation.
/// Disables Activity header propagation on the SocketsHttpHandler to prevent Ocelot
/// from overwriting Datadog trace context headers.
/// </summary>
/// <remarks>
/// <para>
/// v23.0.0 introduced SocketsHttpHandler (previously HttpClientHandler was used).
/// v24.1.0 changed the return type from HttpMessageHandler to SocketsHttpHandler.
/// v25.0.0 keeps the SocketsHttpHandler return type unchanged (only adds net10.0 support).
/// </para>
/// <para>
/// Target method: <see href="https://github.com/ThreeMammals/Ocelot/blob/23.0.0/src/Ocelot/Requester/MessageInvokerPool.cs">MessageInvokerPool.CreateHandler</see>
/// </para>
/// </remarks>
[InstrumentMethod(
    AssemblyName = "Ocelot",
    TypeName = "Ocelot.Requester.MessageInvokerPool",
    MethodName = "CreateHandler",
    ReturnTypeName = "System.Net.Http.HttpMessageHandler",
    ParameterTypeNames = ["Ocelot.Configuration.DownstreamRoute"],
    MinimumVersion = "23.0.0",
    MaximumVersion = "24.0.*",
    IntegrationName = IntegrationName)]
[InstrumentMethod(
    AssemblyName = "Ocelot",
    TypeName = "Ocelot.Requester.MessageInvokerPool",
    MethodName = "CreateHandler",
    ReturnTypeName = "System.Net.Http.SocketsHttpHandler",
    ParameterTypeNames = ["Ocelot.Configuration.DownstreamRoute"],
    MinimumVersion = "24.1.0",
    MaximumVersion = "25.*.*",
    IntegrationName = IntegrationName)]
[Browsable(false)]
[EditorBrowsable(EditorBrowsableState.Never)]
public sealed class OcelotMessageInvokerPoolIntegration
{
    private const string IntegrationName = nameof(Configuration.IntegrationId.HttpMessageHandler);
    private const IntegrationId IntegrationId = Configuration.IntegrationId.HttpMessageHandler;
    private const IntegrationId SocketHandlerIntegrationId = Configuration.IntegrationId.HttpSocketsHandler;

    internal static CallTargetReturn<TReturn> OnMethodEnd<TTarget, TReturn>(TTarget instance, TReturn returnValue, Exception exception, in CallTargetState state)
    {
        // If our HttpClient and SocketsHttpHandler integrations are not enabled, do not modify the factory behavior
        var settings = Tracer.Instance.CurrentTraceSettings.Settings;
        if (!settings.IsIntegrationEnabled(IntegrationId) || !settings.IsIntegrationEnabled(SocketHandlerIntegrationId))
        {
            return new CallTargetReturn<TReturn>(returnValue);
        }

        // On net6.0+, SocketsHttpHandler builds an internal handler chain that includes DiagnosticsHandler
        // when ActivityHeadersPropagator is non-null. DiagnosticsHandler creates Activities and fires
        // DiagnosticSource events, which allows OpenTelemetry SDK (if present) to inject its own trace
        // context headers, overwriting headers already set by our HttpClient instrumentation.
        // Setting the propagator to null (rather than CreateNoOutputPropagator()) prevents
        // DiagnosticsHandler from being added to the chain entirely, ensuring Datadog trace
        // context is preserved and avoiding unnecessary Activity creation for Ocelot's downstream calls.
        if (returnValue is System.Net.Http.SocketsHttpHandler handler)
        {
            handler.ActivityHeadersPropagator = null;
        }

        return new CallTargetReturn<TReturn>(returnValue);
    }
}

#endif