ChildActorExited - Manually killing child PID does not result in ChildActorExited Message to Parent

[bryang-spindance]

Code

Below is example code which has reproduced this issue for me.

Project structure

.
├── app
│   ├── __init__.py
│   ├── parent.py
│   └── child.py
├── start.py
└── stop.py

start.py

from thespian.actors import ActorSystem
from app import parent

if __name__ == '__main__':
  asys = ActorSystem('multiprocTCPBase')
  actor = asys.createActor(parent.Parent)
  asys.tell(actor, parent.Initialize())

stop.py

from thespian.actors import ActorSystem

if __name__ == '__main__':
  ActorSystem('multiprocTCPBase').shutdown()

parent.py

from thespian.actors import ActorTypeDispatcher
import os

class Initialize:
  def __init__(self):
    pass

class Parent(ActorTypeDispatcher):
  def __init__(self, *args, **kwargs):
    super(Parent, self).__init__(*args, **kwargs)
    self._child = None

  def receiveMsg_Initialize(self, msg, sender):
    print(f'{self.myAddress} (P|:{os.getpid()}) Parent received Initialize command from {sender}')
    self._child = self.createActor('app.child.Child')
    self.send(self._child, Initialize())

  def receiveMsg_ChildActorExited(self, msg, sender):
    print(f'In Parent: ChildActorExited')

child.py

from thespian.actors import ActorTypeDispatcher
import os

class Child(ActorTypeDispatcher):
  def __init__(self, *args, **kwargs):
    super(Child, self).__init__(*args, **kwargs)

  def receiveMsg_Initialize(self, msg, sender):
    print(f'{self.myAddress} (P|:{os.getpid()}) Child received Initialize command from {sender}')

Procedure

1. Navigate to the root of my project.

~$ cd ~/Documents/thespian/test

2. Start the actor system using start.py

~/Documents/thespian/test$ python start.py

ActorAddr-(T|:1111) (P|:5555) Parent received Initialize command from ActorAddr-(T|:0000)
ActorAddr-(T|:2222) (P|:6666) Child received Initialize command from ActorAddr-(T|:1111)

3. Kill the child actor process by its PID.

~/Documents/thespian/test$ kill -9 6666

4. After tests, shut down actor system.

~/Documents/thespian/test$ python stop.py

Problem

From the procedure above, upon killing the child process in step 3, it is to my understanding that the parent actor should immediately receive a ChildActorExited message and my example program should print out ChildActorExited to the terminal; this, however, does not happen. Instead the remaining parent actor will stay alive and report nothing.

I have tested this same functionality on MacOS and Windows with the same results. I also tried using multiprocUDPBase but again got the same results.

Another thing to note is after killing the child process and running stop.py, the actor system takes a bit longer than usual to shutdown however it does not print any additional information.

Environment

• These tests were performed in fresh virtual environments where the only pip package installed was thespian.
• I have tested this on MacOS Monterey (12.1) as well as Windows 10 (20H2).
  • On both operating systems, I have tested using various python versions (3.7.3, 3.8.6, 3.9.9).
  • I have also tested on a couple versions of Thespian (3.9.11, 3.10.6).

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If you need any additional information, please let me know.