为请求的持续时间设置全局变量

import threading

class GlobalRequestVariables:
    def __init__(self):
        self._local = threading.local()

    def set_duration(self, duration):
        setattr(self._local, 'duration', duration)

    def get_duration(self):
        return getattr(self._local, 'duration', None)

class RequestDuration:
    def __init__(self, duration):
        self.duration = duration

    def __enter__(self):
        # 设置全局变量
        global request_duration
        request_duration = self.duration

    def __exit__(self, exc_type, exc_value, traceback):
        # 清除全局变量
        global request_duration
        request_duration = None