Alternatively to OpenTelemetry, it seems Java now offers the ability to register events through JFR, which has the advantage of being very lightweight, with apparently no impact whatsoever when tracing is disabled.

Regarding the forwarding of tracing contexts to background threads, at least with opentracing it seems possible.

I discussed this with Bruno Baptista the other day, and he suggested using what he called “links” for the same purpose in OpenTelemety.

Interestingly, there is an independently-developed Hibernate Search plugin for Elastic APM (a tracing solution):

So the need exists for sure.

Note OpenTelemetry should now be preferred to OpenTracing.

Regarding the forwarding of tracing contexts to background threads, at least with opentracing it seems possible.

OpenTracing has a concept of “references” between spans. See https://opentracing.io/specification/

At the moment there are two types of references: “child of” (~ method call, the parent waits for the child span to finish) and “forwards” (~ notification, the parent doesn’t care about the child span).

Interestingly, it would seem that a given span can have multiple references of the same type. So hopefully, when a bulk request is created that groups multiple indexing requests from multiple threads, we will be able to create a new span that references spans from all these threads? That would fit our use case perfectly…