eventlet_spawn_oslo_concurrency_fair_lock.py

import random
import time

import eventlet
from oslo_concurrency import lockutils

eventlet.monkey_patch()

LOCK = "my-lock"

WORKER_NAME = None


@lockutils.synchronized(name=LOCK, fair=True)
def locked_f(name):
    global WORKER_NAME
    if WORKER_NAME:
        raise ValueError(f"{name}: I'm overlapping with {WORKER_NAME}")

    WORKER_NAME = name
    time.sleep(random.randint(0, 10) / 100)
    WORKER_NAME = None


def do_work(name):
    print('starting worker', name)
    while True:
        locked_f(name)
        time.sleep(random.randint(0, 10) / 100)
        print('.', end='')


def test():
    for i in range(2):
        # eventlet.spawn is OK
        # eventlet.spawn(do_work, f"worker{i}")

        # eventlet.spawn_n is NOT OK
        # it is probably https://github.com/eventlet/eventlet/issues/731
        eventlet.spawn_n(do_work, f"worker{i}")

    time.sleep(10)


if __name__ == '__main__':
    test()