Question

我正在开发的应用程序中的一个模块旨在用作Linux上的长时间运行进程，我希望它可以优雅地处理SIGTERM，SIGHUP和其他可能的信号。该程序的核心部分实际上是一个循环，它定期运行一个函数（反过来唤醒另一个线程，但这不太重要）。看起来或多或少是这样的：

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

cleanup_and_exit()

我现在要添加的是捕获SIGTERM并退出循环，就像KeyboardInterrupt异常一样。

我有一个想法是添加一个标志，该标志将由信号处理函数设置为True，并用睡眠（0.1）或其他任何东西替换sleep（60），并使用一个计算秒数的计数器：

_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()

以及其他地方：

def signal_handler(sig, frame): 
    _exit_flag = True

但我不确定这是最好/最有效的方法。

Answer 1

为什么不将清理推送到处理程序中，而不是在主循环中使用sentinel，因此必须比你真正想检查它更频繁地唤醒？类似的东西：

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)

在睡眠循环上实现信号处理

1 个答案: