Allow specifying a context propagator on SocketsHttpHandler

[MihaZupan]

Background and Motivation

We approved the Propagator APIs in #50658, which we are consuming in the HttpClient stack.

The approved API includes a global static property Current.

Some advanced cases require more granular control over which propagator is used - for example only enabling propagation for a given handler/destination/library.
Unit testing of applications/libraries is also difficult without resorting to hacks like RemoteExecutor / writing a custom composite propagator / disabling test parallelization.
To address these scenarios, we propose exposing a property on SocketsHttpHandler to control which propagator is used.

Proposed API

namespace System.Net.Http
{
    public sealed class SocketsHttpHandler
    {
        public DistributedContextPropagator? ActivityHeadersPropagator { get; set; }
    }
}

null means no propagation.

Usage Examples

using var handler = new SocketsHttpHandler
{
    ActivityHeadersPropagator = DistributedContextPropagator.CreatePassThroughPropagator()
};

Alternative Designs

Different names for the property, e.g.

• DistributedContextPropagator? DistributedContextPropagator { get; set; }
  • property name the same as the type name
  • Comment here was that we can be more specific about the property's role specifically for SocketsHttpHandler to hopefully make it easier for users to understand

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Issue Details

---

Background and Motivation

We approved the Propagator APIs in #50658, which we are consuming in the HttpClient stack.

The approved API includes a global static property Current.

Some advanced cases require more granular control over which propagator is used - for example only enabling propagation for a given handler/destination/library.
Unit testing of applications/libraries is also difficult without resorting to hacks like RemoteExecutor / writing a custom composite propagator / disabling test parallelization.
To address these scenarios, we propose exposing a property on SocketsHttpHandler to control which propagator is used.

Proposed API

namespace System.Net.Http
{
    public sealed class SocketsHttpHandler
    {
        public DistributedContextPropagator? ActivityHeaderPropagator { get; set; }
    }
}

null means no propagation.

Usage Examples

using var handler = new SocketsHttpHandler
{
    ActivityHeaderPropagator = DistributedContextPropagator.CreatePassThroughPropagator()
};

Alternative Designs

Different names for the property, e.g.

• DistributedContextPropagator? DistributedContextPropagator { get; set; } - property name same as the type name

Author:	MihaZupan
Assignees:	-
Labels:	api-suggestion, area-System.Net.Http
Milestone:	6.0.0

[karelz]

Update: We changed it to plural -- Headers instead of Header ... discussion with @MihaZupan and @stephentoub

[terrajobst]

• Looks good as proposed

namespace System.Net.Http
{
    public sealed class SocketsHttpHandler
    {
        public DistributedContextPropagator? ActivityHeadersPropagator { get; set; }
    }
}