`tell` method in actor is not working with sleep

[windbird123]

The following code was not working as expected. (ox version: 0.0.24)

import ox.supervised
import ox.channels.*

class Stateful:
  private var counter: Int = 0

  def increment(delta: Int): Int =
    counter += delta
    Thread.sleep(100)
    println(counter)
    counter

supervised {
  val ref = Actor.create(new Stateful)
  ref.tell(_.increment(5))
}

expected results: prints 5
actual results: prints nothing

When Thread.sleep(100) line was removed, it worked as expected.

[adamw]

You're right, the example in the docs is misleading.

What happens there is that because .tell is non-blocking, the invocation is scheduled, and the scope ends (there's not other code to run - the main body is complete). When this happens, all threads that are still running (which includes actors) are interrupted. Hence, the println is never invoked.

[windbird123]

Thank you for your kind explanation.

When I replace Thread.sleep(100) with (1 to 10000000).foreach(println), it seemed like there was no interruption. (It printed all numbers)

 def increment(delta: Int): Int =
    counter += delta
    // Thread.sleep(100)
    (1 to 10000000).foreach(println)
    println(counter)
    counter

I thought that (1 to 10000000).foreach(println) to be interrupted since the scope already ends (and main body is complete).
In this case, could we assume that ox tried to interrupt but was not interrupted.

[adamw]

Interesting! This surprised me as well, but it seems println is not interruptible!

You can observe the interruption e.g. as follows:

    def increment(delta: Int): Int =
      counter += delta
      try Thread.sleep(100)
      catch
        case e: Exception =>
          println("Exception: " + e)
          throw e
      println(counter)
      counter

[adamw]

I've expanded the example (4542e47), I'll close this for now as I think the code is fine, but please reopen if there are some more problems with tell