2 ms·

How does the tooling know to hide the call to "fork" in the scoped task example?

• pron 4y ago
  JDK methods can be annotated as "internal" and optionally hidden in stack-traces, but in this case it's unnecessary. The fork call takes place on the parent thread and isn't part of any stack trace when an exception in a child occurs. The regular structuring of exception stack traces takes care of the rest. Remember that Java has been multithreaded since its inception, and virtual threads don't change any of the threading model. They just make Java threads cheap. It's as if they've been there all along.
  • mgraczyk 4y ago
    Wouldn't the exception actually come from throwIfFailed? Or does it come from resultNow? How does the tool show it as corresponding to the call to findUser?
    • pron 4y ago
      throwIfFailed throws an exception that wraps one thrown by the child as a "caused by" and lists their stack traces. Java users have had this for many years, but threads were simply costly, so they were shared among tasks. The new thing structured concurrency brings -- in addition to making some best practices easier to follow -- is that the runtime now records parent-child relationships among threads (that now make sense when threads are no longer shared). You can see these relationships and the tree hierarchy for the entire application with a new JSON thread-dump.