90 lines
2.8 KiB
Python
90 lines
2.8 KiB
Python
# Copyright 2016 Mirantis, 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 logging
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import threading
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import time
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from oslo_messaging._drivers.zmq_driver import zmq_async
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LOG = logging.getLogger(__name__)
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zmq = zmq_async.import_zmq()
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class TTLCache(object):
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_UNDEFINED = object()
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def __init__(self, ttl=None):
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self._lock = threading.Lock()
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self._cache = {}
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self._executor = None
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if not (ttl is None or isinstance(ttl, (int, float))):
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raise ValueError('ttl must be None or a number')
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# no (i.e. infinite) ttl
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if ttl is None or ttl <= 0:
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ttl = float('inf')
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else:
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self._executor = zmq_async.get_executor(self._update_cache)
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self._ttl = ttl
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if self._executor:
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self._executor.execute()
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@staticmethod
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def _is_expired(expiration_time, current_time):
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return expiration_time <= current_time
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def add(self, key, value=None):
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with self._lock:
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expiration_time = time.time() + self._ttl
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self._cache[key] = (value, expiration_time)
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def get(self, key, default=None):
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with self._lock:
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data = self._cache.get(key)
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if data is None:
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return default
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value, expiration_time = data
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if self._is_expired(expiration_time, time.time()):
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del self._cache[key]
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return default
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return value
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def __contains__(self, key):
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return self.get(key, self._UNDEFINED) is not self._UNDEFINED
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def _update_cache(self):
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with self._lock:
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current_time = time.time()
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old_size = len(self._cache)
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self._cache = \
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{key: (value, expiration_time) for
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key, (value, expiration_time) in self._cache.items()
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if not self._is_expired(expiration_time, current_time)}
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new_size = len(self._cache)
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LOG.debug('Updated cache: current size %(new_size)s '
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'(%(size_difference)s records removed)',
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{'new_size': new_size,
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'size_difference': old_size - new_size})
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time.sleep(self._ttl)
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def cleanup(self):
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if self._executor:
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self._executor.stop()
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