Question

请你定期告知如何定期执行一个比周期性间隔需要更多时间执行的任务？

例如：

def lookup():
    # do some lookups, retrieve info, let's assume it takes 60sec to complete
    msg = {'abc':123}
    time.sleep(60)
    return msg

class Publisher(object):
    def __init__(self):
        self._TIMEIT = 0
        self._INTERVAL = 5
        self._counter = 0

    def xxx():
        t_start = time.time()
        msg = lookup()
        # do something with the value returned
        save_msg_to_db(msg)
        self._counter += 1
        t_end = time.time()
        self._TIMEIT = int(math.ceil(t_end - t_start))

    def run():
        while True:
            # let's do the lookup every 5sec, but remember that lookup takes 60sec to complete
            time.sleep(self._INTERVAL)
            # the call to xxx() should be non-blocking
            xxx()

但run方法负责安排定期任务，并且当它迭代时，它不应该在调用函数xxx时阻塞。

我正在考虑在每次调用xxx函数时创建一个事件循环，如A Bad Coroutine Example中所述但是如何调用xxx非阻塞？

PS。我正在使用Python3.4新的asyncio（过去使用gevent），不确定我是否在这里问愚蠢。

所以lookup会创建一个异步循环，让我们假设60秒完成。但是，在run方法中有一个无限循环运行，我希望它每隔5秒进行一次查找，换句话说我想（1）我多久调用一次查找函数，独立（2）完成查找需要多长时间

Answer 1

由于您的lookup()主要是I / O密集型，因此您可以将xxx()方法作为一个线程运行并且完全正常（代码简化为了简洁）：

import threading
import time

class Publisher(object):

    def __init__(self):
        self._INTERVAL = 5
        self._counter = 0
        self._mutex = threading.Lock()

    def xxx(self):
        msg = lookup()
        save_msg_to_db(msg)
        with self._mutex:  # make sure only one thread is modifying counter at a given time
            self._counter += 1

    def run(self):
        while True:
            time.sleep(self._INTERVAL)
            t = threading.Thread(target=self.xxx)
            t.setDaemon(True)  # so we don't need to track/join threads
            t.start()  # start the thread, this is non-blocking

python：如何定期进行非阻塞查找

1 个答案: