python - 使用multiprocessing.Process调用start方法后，有较小的几率子进程中run方法未执行

Question

继承multiprocessing.Process实现了一个worker类，在父进程中，自己实现了一个最多启动N的限制（出问题的环境是30个）。实际运行中发现，大约有万分之二（当前每天运行46000+次，大约出现11次）的概率，子进程创...

ringa_lee · Answer

La raison a été trouvée. En raison de l'utilisation de thread+mutiprocessing (fork) dans le processus principal, un blocage se produit dans la journalisation. Le phénomène est que la première phrase de journalisation dans le processus enfant se bloque. Le problème ne se produit que sous Linux.
J'ai trouvé la méthode de reproduction après avoir lu cette réponse sur stckoverflow, une autre réponse, la solution
Démo de reproduction :

#coding=utf-8
import os
import time
import logging
import threading
import multiprocessing
import logging.handlers


def init_log(log_path, level=logging.INFO, when="midnight", backup=7,
             format="%(levelname)s:[%(asctime)s][%(filename)s:%(lineno)d][%(process)s][%(thread)d] %(message)s",
             datefmt="%Y-%m-%d %H:%M:%S"):
    formatter = logging.Formatter(format, datefmt)
    logger = logging.getLogger()
    logger.setLevel(level)

    dir = os.path.dirname(log_path)
    if not os.path.isdir(dir):
        os.makedirs(dir)

    handler = logging.handlers.TimedRotatingFileHandler(log_path + ".log",
                                                        when=when,
                                                        backupCount=backup)
    handler.setLevel(level)
    handler.setFormatter(formatter)
    logger.addHandler(handler)


stop = False

class Worker(multiprocessing.Process):
    u"""
    多进程方式执行任务，使用CPU密集型
    """
    def __init__(self):
        super(Worker, self).__init__()
        self.reset_ts = time.time() + 3
        self.stopping = False

    def run(self):
        logging.info('Process pid is %s' % os.getpid())

    def check_timeout(self, now):
        u"""
        若当前时间已超过复位时间，则结束进程
        :param now:
        :return:
        """
        global stop
        if now > self.reset_ts and not self.stopping:
            self.stopping = True
            logging.info('error pid is %s' % os.getpid())
            stop = True


def main():
    global stop
    worker_pool = []
    while 1:
        if worker_pool:
            now = time.time()
            for worker in worker_pool:
                worker.check_timeout(now)
                if stop:
                    logging.error('Process not run, exit!')
                    exit(-1)

        alive_workers = [worker for worker in worker_pool if worker.is_alive()]
        over_workers = list(set(alive_workers) ^ set(worker_pool))
        for over_worker in over_workers:
            over_worker.join()
        worker_pool = alive_workers
        if len(worker_pool) < 1000:
            logging.info('create worker')
            worker = Worker()
            worker.start()
            logging.info('worker pid is %s' % worker.pid)
            worker_pool.append(worker)
        time.sleep(0.001)


class ExecuteThread(threading.Thread):
    def run(self):
        main()

class ExecuteThread2(threading.Thread):
    def run(self):
        global stop
        while 1:
            logging.info('main thread')
            time.sleep(0.001)
            if stop:
                exit(-1)

if __name__ == '__main__':
    init_log('/yourpath/timeout')
    #main()

    thread = ExecuteThread()
    thread2 = ExecuteThread2()
    thread.start()
    thread2.start()
    thread.join()
    thread2.join()

Après la reproduction, n'oubliez pas d'effacer le processus bloqué....