engine/test_mp.py

import multiprocessing
import os
import time

def worker(result_queue):
    print(f"Child process pid {os.getpid()} starting...")
    try:
        result_queue.put(f"Success from pid {os.getpid()}")
    except Exception as e:
        result_queue.put(f"Error: {e}")

if __name__ == "__main__":
    # Explicitly use 'spawn' as it is the default on Windows
    # and what's causing the issue with nested functions.
    multiprocessing.set_start_method('spawn', force=True)
    q = multiprocessing.Queue()
    p = multiprocessing.Process(target=worker, args=(q,))
    print(f"Parent process pid {os.getpid()} starting child...")
    p.start()
    p.join(timeout=10)
    if p.is_alive():
        print("Process timed out!")
        p.terminate()
        p.join()
    elif not q.empty():
        print(f"Result: {q.get()}")
    else:
        print("No result in queue after process finished")
    
    q.close()
    try:
        q.join_thread()
    except: pass
    print("Test finished.")