89 lines
2.4 KiB
Python
89 lines
2.4 KiB
Python
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# Copyright 2013 Red Hat, Inc.
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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 abc
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import collections
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import threading
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import six
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@six.add_metaclass(abc.ABCMeta)
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class Pool(object):
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"""A thread-safe object pool.
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Modelled after the eventlet.pools.Pool interface, but designed to be safe
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when using native threads without the GIL.
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Resizing is not supported.
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"""
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def __init__(self, max_size=4):
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super(Pool, self).__init__()
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self._max_size = max_size
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self._current_size = 0
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self._cond = threading.Condition()
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self._items = collections.deque()
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def put(self, item):
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"""Return an item to the pool."""
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with self._cond:
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self._items.appendleft(item)
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self._cond.notify()
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def get(self):
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"""Return an item from the pool, when one is available.
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This may cause the calling thread to block.
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"""
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with self._cond:
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while True:
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try:
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return self._items.popleft()
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except IndexError:
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pass
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if self._current_size < self._max_size:
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self._current_size += 1
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break
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# FIXME(markmc): timeout needed to allow keyboard interrupt
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# http://bugs.python.org/issue8844
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self._cond.wait(timeout=1)
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# We've grabbed a slot and dropped the lock, now do the creation
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try:
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return self.create()
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except Exception:
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with self._cond:
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self._current_size -= 1
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raise
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def iter_free(self):
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"""Iterate over free items."""
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with self._cond:
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while True:
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try:
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yield self._items.popleft()
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except IndexError:
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break
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@abc.abstractmethod
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def create(self):
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"""Construct a new item."""
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