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48 lines
1.2 KiB
48 lines
1.2 KiB
5 years ago
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import datetime
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class NeverExpires(object):
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def expired(self):
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return False
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class Timer(object):
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"""
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A simple timer that will indicate when an expiration time has passed.
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"""
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def __init__(self, expiration):
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'Create a timer that expires at `expiration` (UTC datetime)'
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self.expiration = expiration
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@classmethod
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def after(cls, elapsed):
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"""
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Return a timer that will expire after `elapsed` passes.
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"""
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return cls(datetime.datetime.utcnow() + elapsed)
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def expired(self):
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return datetime.datetime.utcnow() >= self.expiration
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class LockTimeout(Exception):
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'An exception when a lock could not be acquired before a timeout period'
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class LockChecker(object):
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"""
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Keep track of the time and detect if a timeout has expired
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"""
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def __init__(self, session_id, timeout):
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self.session_id = session_id
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if timeout:
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self.timer = Timer.after(timeout)
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else:
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self.timer = NeverExpires()
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def expired(self):
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if self.timer.expired():
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raise LockTimeout(
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'Timeout acquiring lock for %(session_id)s' % vars(self))
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return False
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