Question

我期待：

制作自定义计时器包装器，用于记录/其他计时目的
如果包装的操作超过预定义的时间长度，则包括抢先退出

这是我到目前为止所做的：

from contextlib import ContextDecorator
import datetime

from tornado import gen, ioloop
from tornado.concurrent import Future


class timing_logger(ContextDecorator):
    def __init__(self, allowed_ms):
        self.allowed_ms = allowed_ms
        self.f = Future()
        # this exception is not bubbled up by Tornado but fires
        gen.with_timeout(datetime.timedelta(seconds=1+allowed_ms/1000), self.f)

    def __enter__(self):
        self.start_time = datetime.datetime.now()
        return self

    def __exit__(self, exc_type, exc_val, traceback):
        self.f.set_result(True)
        elapsed_time_ms = (datetime.datetime.now() - self.start_time).total_seconds() * 1000

        if exc_type == gen.TimeoutError:
            raise TimeoutError('ruh oh, this is reeeally bad')

        if elapsed_time_ms > self.allowed_ms:
            raise TimeoutError('took {actual} ms, but was only allowed {allowed}.'.format(
                 actual=elapsed_time_ms, allowed=self.allowed_ms))

        else:
            print('worked. nothing to see here...')
        return False


@gen.coroutine
def main():

    with timing_logger(1000):
        # real application may be a variety of coroutines
        # and regular function calls, some of which may hang
        # for a long time
        for i in range(25):
            yield gen.sleep(0.1)


if __name__ == "__main__":
    ioloop.IOLoop.current().run_sync(
        lambda: main())

我在这里遇到的问题是因为我没有放弃gen.with_timeout未来，我在堆栈中看到：

$python test.py 
ERROR:tornado.application:Future <tornado.concurrent.Future object at 0x10c7cb668> exception was never retrieved: tornado.gen.TimeoutError: Timeout
Traceback (most recent call last):
  File "test.py", line 48, in <module>
    lambda: main())
<snip>
    yielded = self.gen.send(value)
  File "test.py", line 43, in main
    yield gen.sleep(0.1)
  File "test.py", line 28, in __exit__
    actual=elapsed_time_ms, allowed=self.allowed_ms))
TimeoutError: took 2606.2940000000003 ms, but was only allowed 1000.

龙卷风超时不正在＆＃34;冒泡＆＃34; （缺乏更好的词）。

我希望__exit__捕获异常，以便我可以处理它并进行适当的记录，同时重新提升为不同的异常类型。

我不确定是否需要：

根本不使用ContextDecorator
做一些与龙卷风召唤的方式/地点不同的事情
????

我知道在这个例子中，我可以将所有调用代码包装到协程中，并在定时记录器包装周围为main函数添加超时，如下所示：

@gen.coroutine
def main():


    @gen.coroutine
    def f():
        with timing_logger(1000):
            # real application may be a variety of coroutines
            # and regular function calls, some of which may hang
            # for a long time
            for i in range(25):
                yield gen.sleep(0.1)

    future = f()
    yield gen.with_timeout(datetime.timedelta(seconds=1), future)

但我希望将上述内容包含在我的ContextDecorator中，因为必须将其复制到我想要使用的所有内容timing_logger，这样会变得乏味且容易出错。

如何实现所需的功能以允许我的ContextDecorator将超时作为其功能的一部分包含在内？

使用Python 3.6.1和最新的Tornado（4.5.1）。

Answer 1

不是使用龙卷风超时，而是使用signal来中断并触发此异常（尽管alarm only allows integer, second inputs）：

    def timeout_handler(signum, frame):
        raise gen.TimeoutError()

    self.signal = signal.signal(signal.SIGALRM, timeout_handler)
    signal.alarm(1 + self.allowed_ms // 1000)

这将适当地引发异常，从而产生一个完整的ContextDecorator，如下所示：

from contextlib import ContextDecorator
import datetime

from tornado import gen, ioloop
from tornado.concurrent import Future


class timing_logger(ContextDecorator):
    def __init__(self, allowed_ms):
        self.allowed_ms = allowed_ms
        self.f = Future()
        # this exception is not bubbled up by Tornado but fires
        gen.with_timeout(datetime.timedelta(seconds=1+allowed_ms/1000), self.f)

    def __enter__(self):
        self.start_time = datetime.datetime.now()
        def timeout_handler(signum, frame):
            raise gen.TimeoutError()  # could be any type of exception

        self.signal = signal.signal(signal.SIGALRM, timeout_handler)
        signal.alarm(1 + self.allowed_ms // 1000)

        return self

    def __exit__(self, exc_type, exc_val, traceback):
        signal.alarm(0)
        self.f.set_result(True)
        elapsed_time_ms = (datetime.datetime.now() - self.start_time).total_seconds() * 1000

        if exc_type == gen.TimeoutError:
            raise TimeoutError('ruh oh, this is reeeally bad')

        if elapsed_time_ms > self.allowed_ms:
            raise TimeoutError('took {actual} ms, but was only allowed {allowed}.'.format(
                 actual=elapsed_time_ms, allowed=self.allowed_ms))

        else:
            print('worked. nothing to see here...')
        return False

请注意，您需要在__exit__中重置警报，否则它将在您的代码中稍后触发。

如何在ContextDecorator中引发Tornado超时异常？

1 个答案: