Remove ActivityPropagationHandler breaking change

[leastprivilege]

We have been using the activity handler with the IHttpForwarder.

Could you elaborate how to deal with this in RC.1 for both .NET 6 and earlier?

thanks!

[MihaZupan]

Hi,

We originally added the handler to YARP as a workaround to bridge the gap in SocketsHttpHandler, where it couldn't make use of distributed tracing out of the box.
The good news is that we made a lot of improvements in the area for the 6.0 release with the introduction of the DistributedContextPropagator class. As part of the change, we enabled distributed tracing on SocketsHttpHandler by default as well, including the option to configure it via the ActivityHeadersPropagator property.

As such, the scenario is expected to "just work" in YARP on .NET 6.0 and newer by default, there is no need to use workarounds like the ActivityPropagationHandler.

For versions before 6.0, YARP will work as a silent pass-through for distributed tracing by default - the trace will not be broken, but the proxy will not participate in it either.
See updated docs for getting YARP to actively participate.

Can you also describe how you are currently using the handler (just setting the config flag, wrapping the handler manually, using vendor-specific distributed tracing packages ...)?

[karelz]

It may be worth saying that we plan to document the above workaround for YARP active participation in distributed tracing on .NET 5/.NET Core 3.1 in YARP docs.

[leastprivilege]

Thanks @MihaZupan for the explanation.

We will wire up the handler manually for non-NET6 scenarios.

Can you also describe how you are currently using the handler

We are using it internally for forward local API calls to remote APIs in our BFF product
https://github.com/DuendeSoftware/BFF/blob/6dde5ccf527121a275d48a79262f46bff6c59c4f/src/Duende.Bff.Yarp/RemoteApiEndpoint.cs#L74

[MihaZupan]

FYI we added more documentation with a more capable workaround here: https://github.com/microsoft/reverse-proxy/blob/main/docs/docfx/articles/distributed-tracing.md