I guess it's not a specific babashka question so you could also try #C03S1KBA2 or even StackOverflow (it's basically a general Java question) if you don't get good answers here

Agreed, just thought I'd start here since I've seen a few discussions about the virtual threads here earlier! Thanks

yeah no problem

I would suggest you try to limit the number of such requests at a higher level, perhaps by using a bounded queue.

One simple usage of a bounded queue is in the source of tap>

(defn tap>
...
  (force tap-loop)
  (.offer tapq (if (nil? x) ::tap-nil x)))

(defonce ^:private ^java.util.concurrent.ArrayBlockingQueue tapq (java.util.concurrent.ArrayBlockingQueue. 1024))

It is recommended to use Semaphores to control concurrency https://blogs.oracle.com/javamagazine/post/java-loom-virtual-threads-platform-threads Check the section "Three pieces of practical advice".

nice! this class is already available in bb btw, so it should work, I think

Usually you should not need to, you can run millions of them in fact. If target resource needs to be controlled for concurrency (like connection or so) semaphore is a good option.

...also bounds can be set using structured concurrency pattern (StructuredTaskScope) I don't know if this is supported in babashka though.

not sure, but semaphore should work. countdownlatch could also work, but this is not in bb yet I think

StructuredTaskScope I think it's a bit clumsy for use in Lisp. It's too javaish. But I can imagine some sort of macro that can do this in elegant Lispy way.

This would be a nice research project

I'd just shell out to tar , it's available on pretty much any system including Windows

OK.