Description

When trying to trace JGroups communications, I found that the spans created are never made "current", and due to that all nested communications in JGroups isn't shown as nested, but on the same level.

Implementation ideas

Make the span current while calling the JGroups stack below, and then closing it before returning the async call.

With this setup the called methods will make their new spans nested to the current span created by ISPN.

I found this when working on keycloak/keycloak#39659. The workaround applied there to make the spans current in OpenTelemetrySpan.java on creation of the span is a workaround if only synchronous calls are make, but will fail with asynchronous calls.

I will create a PR with a suggestion.