show_shutdown_executor_futures.py

"""Requires
https://github.com/aeros/cpython/tree/bpo39349-add-cancel_futures-to-Executor.shutdown.
See https://github.com/python/cpython/pull/18057 for details.
"""

import concurrent.futures as cf
import time


def wait_return(duration, result):
    time.sleep(duration)
    return result


def show_executor_shutdown(executor_type, wait, cancel_futures):
    executor = executor_type(max_workers=2)
    futures = [executor.submit(wait_return, .1, 42) for _ in range(8)]
    executor.shutdown(wait=wait, cancel_futures=cancel_futures)
    for fut in futures:
        print(f"{fut._result=}, {fut._state=}")


if __name__ == "__main__":
    print("ThreadPoolExecutor:")
    print("wait=True and cancel_futures=False:")
    show_executor_shutdown(executor_type=cf.ThreadPoolExecutor,
                            wait=True,
                            cancel_futures=False)
    print()
    
    print("wait=True and cancel_futures=True:")
    show_executor_shutdown(executor_type=cf.ThreadPoolExecutor,
                            wait=True,
                            cancel_futures=True)
    print()
    
    print("wait=False and cancel_futures=False:")
    show_executor_shutdown(executor_type=cf.ThreadPoolExecutor,
                            wait=False,
                            cancel_futures=False)
    print()
    
    print("wait=False and cancel_futures=True:")
    show_executor_shutdown(executor_type=cf.ThreadPoolExecutor,
                            wait=False,
                            cancel_futures=True)
    print()

    print("ProcessPoolExecutor:")
    print("wait=True and cancel_futures=False:")
    show_executor_shutdown(executor_type=cf.ProcessPoolExecutor,
                            wait=True,
                            cancel_futures=False)
    print()

    print("wait=True and cancel_futures=True:")
    show_executor_shutdown(executor_type=cf.ProcessPoolExecutor,
                            wait=True,
                            cancel_futures=True)
    print()
    
    # Note: wait=False was omitted for PPE due to deadlocks.
    # See https://gist.github.com/aeros/d1ff62b730426584413bca0c8f2ed99d
    # for an example.

Specs:
Python 3.9+ (PR branch for python/cpython#18057)
Linux kernel 5.4.8
Intel i5-4460

Results:

[aeros:~/repos/aeros-cpython]$ ./python show_executor_shutdown.py
ThreadPoolExecutor:
wait=True and cancel_futures=False:
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'

wait=True and cancel_futures=True:
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'

wait=False and cancel_futures=False:
fut._result=None, fut._state='RUNNING'
fut._result=None, fut._state='RUNNING'
fut._result=None, fut._state='PENDING'
fut._result=None, fut._state='PENDING'
fut._result=None, fut._state='PENDING'
fut._result=None, fut._state='PENDING'
fut._result=None, fut._state='PENDING'
fut._result=None, fut._state='PENDING'

wait=False and cancel_futures=True:
fut._result=None, fut._state='RUNNING'
fut._result=None, fut._state='RUNNING'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'
fut._result=None, fut._state='CANCELLED'

ProcessPoolExecutor:
wait=True and cancel_futures=False:
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'

wait=True and cancel_futures=True:
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=42, fut._state='FINISHED'
fut._result=None, fut._state='CANCELLED_AND_NOTIFIED'
fut._result=None, fut._state='CANCELLED_AND_NOTIFIED'
fut._result=None, fut._state='CANCELLED_AND_NOTIFIED'
fut._result=None, fut._state='CANCELLED_AND_NOTIFIED'
fut._result=None, fut._state='CANCELLED_AND_NOTIFIED'