为什么我的多进程队列看起来不是线程安全的？

Question

我正在构建一个运行另一个Python程序的监视程序计时器，如果它无法从任何线程中找到签入，则关闭整个程序。这样，它最终将能够控制所需的通信端口。计时器的代码如下：

from multiprocessing import Process, Queue
from time import sleep
from copy import deepcopy

PATH_TO_FILE = r'.\test_program.py'
WATCHDOG_TIMEOUT = 2

class Watchdog:

    def __init__(self, filepath, timeout):
        self.filepath = filepath
        self.timeout = timeout
        self.threadIdQ = Queue()
        self.knownThreads = {}

    def start(self):
        threadIdQ = self.threadIdQ

        process = Process(target = self._executeFile)
        process.start()
        try:
            while True:
                unaccountedThreads = deepcopy(self.knownThreads)

                # Empty queue since last wake. Add new thread IDs to knownThreads, and account for all known thread IDs
                # in queue
                while not threadIdQ.empty():
                    threadId = threadIdQ.get()
                    if threadId in self.knownThreads:
                        unaccountedThreads.pop(threadId, None)
                    else:
                        print('New threadId < {} > discovered'.format(threadId))
                        self.knownThreads[threadId] = False

                # If there is a known thread that is unaccounted for, then it has either hung or crashed.
                # Shut everything down.
                if len(unaccountedThreads) > 0:
                    print('The following threads are unaccounted for:\n')
                    for threadId in unaccountedThreads:
                        print(threadId)
                    print('\nShutting down!!!')
                    break
                else:
                    print('No unaccounted threads...')

                sleep(self.timeout)

        # Account for any exceptions thrown in the watchdog timer itself
        except:
            process.terminate()
            raise

        process.terminate()


    def _executeFile(self):
        with open(self.filepath, 'r') as f:
            exec(f.read(), {'wdQueue' : self.threadIdQ})

if __name__ == '__main__':
    wd = Watchdog(PATH_TO_FILE, WATCHDOG_TIMEOUT)
    wd.start()

我还有一个小程序来测试看门狗功能

from time import sleep
from threading import Thread
from queue import SimpleQueue

Q_TO_Q_DELAY = 0.013

class QToQ:

    def __init__(self, processQueue, threadQueue):
        self.processQueue = processQueue
        self.threadQueue = threadQueue
        Thread(name='queueToQueue', target=self._run).start()

    def _run(self):
        pQ = self.processQueue
        tQ = self.threadQueue
        while True:
            while not tQ.empty():
                sleep(Q_TO_Q_DELAY)
                pQ.put(tQ.get())

def fastThread(q):
    while True:
        print('Fast thread, checking in!')
        q.put('fastID')
        sleep(0.5)

def slowThread(q):
    while True:
        print('Slow thread, checking in...')
        q.put('slowID')
        sleep(1.5)

def hangThread(q):
    print('Hanging thread, checked in')
    q.put('hangID')
    while True:
        pass

print('Hello! I am a program that spawns threads!\n\n')

threadQ = SimpleQueue()

Thread(name='fastThread', target=fastThread, args=(threadQ,)).start()
Thread(name='slowThread', target=slowThread, args=(threadQ,)).start()
Thread(name='hangThread', target=hangThread, args=(threadQ,)).start()

QToQ(wdQueue, threadQ)

正如您所看到的，我需要将线程放入queue.Queue，而单独的对象会慢慢将queue.Queue的输出提供给多处理队列。相反，如果我将线程直接放入多处理队列中，或者在put之间没有QToQ对象休眠，则多处理队列将锁定，并且在看门狗端看起来总是为空。

现在，由于多处理队列应该是线程和进程安全的，我只能假设我在实现中搞砸了一些东西。我的解决方案似乎有效，但也觉得hacky足够我觉得我应该解决它。

我正在使用Python 3.7.2，如果重要的话。

Answer 1

我怀疑test_program.py退出。

我把最后几行更改为：

tq = threadQ
# tq = wdQueue    # option to send messages direct to WD

t1 = Thread(name='fastThread', target=fastThread, args=(tq,))
t2 = Thread(name='slowThread', target=slowThread, args=(tq,))
t3 = Thread(name='hangThread', target=hangThread, args=(tq,))

t1.start()
t2.start()
t3.start()
QToQ(wdQueue, threadQ)

print('Joining with threads...')
t1.join()
t2.join()
t3.join()

print('test_program exit')

对join()的调用意味着测试程序永远不会自行退出，因为没有任何线程退出。

因此，t3挂起并且看门狗程序检测到这一点并检测到未计入的线程并停止测试程序。

如果从上面的程序中删除了t3，那么其他两个线程表现良好，看门狗程序允许测试程序无限期地继续。