starts n processes with some random amount of work, and they exit whenever the first one is finished

parallel-wait.py

import os
import random
import time

from multiprocessing import Pool, Event


def init_pool_processes(the_shutdown_event):
    '''
    Initialize each process with the global shutdown event
    '''
    global shutdown_event
    shutdown_event = the_shutdown_event


def wait(ignored):
    sleep_time = random.randint(1, 16)
    sleep_time_left = sleep_time
    print(f"😴 Sleeping for {sleep_time} seconds...")

    while True:
        if shutdown_event.is_set():
            print("💀 Shutdown event set, exiting...")
            return

        if sleep_time_left <= 0:
            print(f"😃 Done sleeping for {sleep_time} seconds!")
            break

        time.sleep(1)
        sleep_time_left -= 1

    shutdown_event.set()


# starts a pool of n processes with some random amount of work, and they all stop as soon
# as the first one is finished
if __name__ == '__main__':
    print(f"👷‍♂️ Starting {os.cpu_count()} worker processes")
    shutdown_event = Event()

    with Pool(processes=os.cpu_count(), initializer=init_pool_processes, initargs=(shutdown_event,)) as pool:
        pool.map(wait, range(os.cpu_count()))
        pool.close()
        pool.join()

race-processors.py

import os
import random
import time

from multiprocessing import Pool, Event

MAX_WAIT = 32

def pretend_uninterruptible_sleep(sleep_time) -> int:
    start_time = time.time()

    while True:
        elapsed_time = time.time() - start_time
        if elapsed_time > sleep_time:
            return elapsed_time

def wait(cpu_num):
    sleep_time = random.randint(16, MAX_WAIT)
    print(f"😴 CPU {cpu_num} sleeping for {sleep_time} seconds...")

    # pretend that this is black box code where we can't just check for a shutdown event
    elapsed_time = pretend_uninterruptible_sleep(sleep_time)

    print(f"😃 Done sleeping for {sleep_time} seconds!")
    return (cpu_num, elapsed_time)


# starts a pool of n processes with some random amount of work, and they all stop as soon
# as the first one is finished
if __name__ == '__main__':
    print(f"👷‍♂️ Starting {os.cpu_count()} worker processes")

    with Pool() as pool:
        for (winner_cpu_num, elapsed_time) in pool.imap_unordered(wait, range(os.cpu_count())): # this is a generator
            print(f"🏆 Winner: CPU {winner_cpu_num} in {elapsed_time:.2f}s")
            break

        print("🔪 Brutalizing the pool")
        pool.terminate()