de4b2848e0
All changes are based on comments from Ie3e6c8a3671bc28bfd6967e8758c1419c3c8d501 TrivialFix Co-Authored-By: Pavel Kholkin <pkholkin@mirantis.com> Change-Id: I2fb44c736d3c15edab5c41ba99e73daed38f7258
85 lines
2.5 KiB
Python
85 lines
2.5 KiB
Python
# Copyright 2015 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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"""dogpile.cache backend that uses dictionary for storage"""
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from dogpile.cache import api
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from oslo_utils import timeutils
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__all__ = [
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'DictCacheBackend'
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]
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# Value for nonexistent and expired keys
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NO_VALUE = api.NO_VALUE
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class DictCacheBackend(api.CacheBackend):
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"""A DictCacheBackend based on dictionary.
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Arguments accepted in the arguments dictionary:
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:param expiration_time: interval in seconds to indicate maximum
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time-to-live value for each key in DictCacheBackend.
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Default expiration_time value is 0, that means that all keys have
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infinite time-to-live value.
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:type expiration_time: real
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"""
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def __init__(self, arguments):
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self.expiration_time = arguments.get('expiration_time', 0)
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self.cache = {}
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def get(self, key):
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"""Retrieves the value for a key or NO_VALUE for nonexistent and
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expired keys.
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:param key: dictionary key
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"""
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(value, timeout) = self.cache.get(key, (NO_VALUE, 0))
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if self.expiration_time > 0 and timeutils.utcnow_ts() >= timeout:
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self.cache.pop(key, None)
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return NO_VALUE
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return value
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def set(self, key, value):
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"""Sets the value for a key.
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Expunges expired keys during each set.
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:param key: dictionary key
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:param value: value associated with the key
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"""
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self._clear()
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timeout = 0
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if self.expiration_time > 0:
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timeout = timeutils.utcnow_ts() + self.expiration_time
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self.cache[key] = (value, timeout)
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def delete(self, key):
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"""Deletes the value associated with the key if it exists.
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:param key: dictionary key
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"""
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self.cache.pop(key, None)
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def _clear(self):
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"""Expunges expired keys."""
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now = timeutils.utcnow_ts()
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for k in list(self.cache):
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(_value, timeout) = self.cache[k]
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if timeout > 0 and now >= timeout:
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del self.cache[k]
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