4eb0ca21b3
Instead of doing [acquire, try, finally, release] just use the condition variable as a context manager to achieve the same effect with less code and with less verbosity. Change-Id: I0a3bb80a932a3dc6623ba2378afa0341e9e06e5a
69 lines
2.2 KiB
Python
69 lines
2.2 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2014 Yahoo! Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import threading
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from taskflow.types import timing as tt
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class Latch(object):
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"""A class that ensures N-arrivals occur before unblocking.
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TODO(harlowja): replace with http://bugs.python.org/issue8777 when we no
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longer have to support python 2.6 or 2.7 and we can only support 3.2 or
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later.
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"""
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def __init__(self, count):
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count = int(count)
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if count <= 0:
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raise ValueError("Count must be greater than zero")
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self._count = count
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self._cond = threading.Condition()
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@property
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def needed(self):
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"""Returns how many decrements are needed before latch is released."""
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return max(0, self._count)
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def countdown(self):
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"""Decrements the internal counter due to an arrival."""
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with self._cond:
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self._count -= 1
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if self._count <= 0:
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self._cond.notify_all()
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def wait(self, timeout=None):
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"""Waits until the latch is released.
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NOTE(harlowja): if a timeout is provided this function will wait
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until that timeout expires, if the latch has been released before the
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timeout expires then this will return True, otherwise it will
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return False.
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"""
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w = None
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if timeout is not None:
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w = tt.StopWatch(timeout).start()
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with self._cond:
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while self._count > 0:
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if w is not None:
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if w.expired():
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return False
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else:
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timeout = w.leftover()
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self._cond.wait(timeout)
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return True
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