在睡眠循環上實現信號處理

Question

我正在開發的應用程序中的一個模塊旨在用作Linux上長時間運行的進程，我希望它能夠優雅地處理SIGTERM，SIGHUP和其他信號。 該程序的核心部分實際上是一個循環，該循環定期運行一個函數（依次喚醒另一個線程，但這並不重要）。 看起來或多或少是這樣的：

while True: 
    try:
        do_something()
        sleep(60)
    except KeyboardInterrupt:
        break

cleanup_and_exit()

我現在要添加的是捕獲SIGTERM並退出循環，就像KeyboardInterrupt異常一樣。

我想到的一個想法是添加一個將由信號處理程序函數設置為True的標志，並用計數秒的計數器將sleep（60）替換為sleep（0.1）或其他內容：

_exit_flag = False
while not _exit_flag: 
    try:
        for _ in xrange(600): 
            if _exit_flag: break
            do_something()
            sleep(0.1)

    except KeyboardInterrupt:
        break

cleanup_and_exit()

還有其他地方：

def signal_handler(sig, frame): 
    _exit_flag = True

但是我不確定這是最好/最有效的方法。

Answer 1

與其在主循環中使用哨兵，而不必比您真正想要檢查的次數更頻繁地喚醒，為什么不將清理推入處理程序？ 就像是：

class BlockingAction(object):

    def __new__(cls, action):

        if isinstance(action, BlockingAction):
           return action
        else:
           new_action = super(BlockingAction, cls).__new__(cls)
           new_action.action = action
           new_action.active = False
           return new_action

    def __call__(self, *args, **kwargs):

        self.active = True
        result = self.action(*args, **kwargs)
        self.active = False
        return result

class SignalHandler(object):

    def __new__(cls, sig, action):

        if isinstance(action, SignalHandler):
            handler = action
        else:
            handler = super(SignalHandler, cls).__new__(cls)
            handler.action = action
            handler.blocking_actions = []
        signal.signal(sig, handler)
        return handler

    def __call__(self, signum, frame):

        while any(a.active for a in self.blocking_actions):
            time.sleep(.01)
        return self.action()

    def blocks_on(self, action):

        blocking_action = BlockingAction(action)
        self.blocking_actions.append(blocking_action)
        return blocking_action

def handles(signal):

    def get_handler(action):

        return SignalHandler(signal, action)

    return get_handler

@handles(signal.SIGTERM)
@handles(signal.SIGHUP)
@handles(signal.SIGINT)
def cleanup_and_exit():
    # Note that this assumes that this method actually exits the program explicitly
    # If it does not, you'll need some form of sentinel for the while loop
    pass

@cleanup_and_exit.blocks_on
def do_something():
    pass

while True:
    do_something()
    time.sleep(60)