Python Multiprocessing.Queue.get - 超时和阻塞不起作用？

Question

我正在构建一个运行多个进程的应用程序。这些进程通过队列传递对象。一切正常。除了我需要进程在输入队列为空时停留一段时间之外。 queue.get() 方法是在一个无限循环中实现的，但我需要这个循环每隔一段时间运行即使他们在队列中没有输入能够运行一些管理代码。

所以本质上它是一个无限循环，需要在 queue.get() 处阻塞至少一秒钟，并在有输入时做一些事情，否则做一些其他事情。

问题是：超时似乎不起作用：

  while True:
            # Process input queue, but make sure to continue the loop once every second if the queue is empty
            wd_input = None
            try:
                wd_input = self.input_queue.get(block=True, timeout=1)
            except Empty:                    
                logging.debug(f"Watchdog queue empty. (interval: {interval.microseconds} microseconds)")

为清楚起见，我删除了一些代码。请相信我，我正在记录 Empty 异常之间的间隔。我得到这个输出：

[2022-05-04 09:35:27,648] DEBUG: Watchdog queue empty. (interval: 1412 microseconds)
[2022-05-04 09:35:28,650] DEBUG: Watchdog queue empty. (interval: 1306 microseconds)
[2022-05-04 09:35:29,651] DEBUG: Watchdog queue empty. (interval: 1417 microseconds)
[2022-05-04 09:35:30,652] DEBUG: Watchdog queue empty. (interval: 1329 microseconds)
[2022-05-04 09:35:31,654] DEBUG: Watchdog queue empty. (interval: 1323 microseconds)
[2022-05-04 09:35:32,655] DEBUG: Watchdog queue empty. (interval: 1318 microseconds)
[2022-05-04 09:35:33,656] DEBUG: Watchdog queue empty. (interval: 1324 microseconds)
[2022-05-04 09:35:34,658] DEBUG: Watchdog queue empty. (interval: 1322 microseconds)
[2022-05-04 09:35:35,659] DEBUG: Watchdog queue empty. (interval: 1308 microseconds)

这与我想要达到的 1 秒相去甚远。本质上，这也是文档所说的：

If timeout is a positive number, it blocks at most timeout seconds and raises the queue.Empty exception if no item was available within that time. (https://docs.python.org/3/library/multiprocessing.html#multiprocessing.Queue)

所以这也许是预料之中的。我想要的不是最多等待超时秒数，而是至少等待超时秒数。这可能吗？如何做到这一点？

Answer 1

我不知道这个interval.microseconds是什么，你正在打印出来。但是您是否注意到实际调试消息上的时间戳？这些消息似乎在几毫秒内每秒输出一次。

import logging
import time
from queue import Queue, Empty

logging.basicConfig(format='%(asctime)s %(message)s')

q = Queue()

for _ in range(5):
    try:
        t0 = time.time()
        msg = q.get(timeout=1)
    except Empty:
        t1 = time.time()
        logging.warning(f'is when this queue empty event was logged. Elapsed = {t1 - t0}')

打印：

2022-05-04 07:24:05,768 is when this queue empty event was logged. Elapsed = 1.000537395477295
2022-05-04 07:24:06,769 is when this queue empty event was logged. Elapsed = 1.0004637241363525
2022-05-04 07:24:07,770 is when this queue empty event was logged. Elapsed = 1.000412940979004
2022-05-04 07:24:08,771 is when this queue empty event was logged. Elapsed = 1.000406265258789
2022-05-04 07:24:09,772 is when this queue empty event was logged. Elapsed = 1.000260591506958

Python Multiprocessing.Queue.get - 超时和阻塞不起作用？

Python Multiprocessing.Queue.get - timeout and blocking not working?

python

queue

multiprocessing

python-3.x