The class com.twitter.util.Future has a method Future.trace(), return type is com.twitter.util.Future.Tracer (this can be found in the compiled Java class)
However, I couldn't find that method in the original Scala code or in the doc. Do you know where I can find the usage or source code for that method?
Why I'm doing this: I'm trying to implement my own tracing framework using Finagle trace.
Future.trace is actually an old member of the Future object. It was used to enable registration of call stack every time you link two asynchronous computations together with map/flatMap. This feature wasn't very popular, so we just remove it.
If you want to look at a tracing Framework you should look at zipkin, and finagle-zipkin that's basically an open-source implementation of Google's Dapper (See paper)