123 lines
3.6 KiB
Python
123 lines
3.6 KiB
Python
# Copyright (c) 2017 Dell Inc. or its subsidiaries.
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# 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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"""
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SimpleCache utility class for Dell EMC ScaleIO Driver.
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"""
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import datetime
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from oslo_log import log as logging
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from oslo_utils import timeutils
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LOG = logging.getLogger(__name__)
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class SimpleCache(object):
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def __init__(self, name, age_minutes=30):
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self.cache = {}
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self.name = name
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self.age_minutes = age_minutes
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def __contains__(self, key):
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"""Checks if a key exists in cache
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:param key: Key for the item being checked.
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:return: True if item exists, otherwise False
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"""
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return key in self.cache
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def _remove(self, key):
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"""Removes item from the cache
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:param key: Key for the item being removed.
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:return:
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"""
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if self.__class__(key):
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del self.cache[key]
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def _validate(self, key):
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"""Validate if an item exists and has not expired.
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:param key: Key for the item being requested.
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:return: The value of the related key, or None.
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"""
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if key not in self:
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return None
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# make sure the cache has not expired
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entry = self.cache[key]['value']
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now = timeutils.utcnow()
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age = now - self.cache[key]['date']
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if age > datetime.timedelta(minutes=self.age_minutes):
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# if has expired, remove from cache
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LOG.debug("Removing item '%(item)s' from cache '%(name)s' "
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"due to age",
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{'item': key,
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'name': self.name})
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self._remove(key)
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return None
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return entry
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def purge(self, key):
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"""Purge an item from the cache, regardless of age
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:param key: Key for the item being removed.
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:return:
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"""
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self._remove(key)
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def purge_all(self):
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"""Purge all items from the cache, regardless of age
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:return:
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"""
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self.cache = {}
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def set_cache_period(self, age_minutes):
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"""Define the period of time to cache values for
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:param age_minutes: Number of minutes to cache items for.
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:return:
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"""
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self.age_minutes = age_minutes
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def update(self, key, value):
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"""Update/Store an item in the cache
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:param key: Key for the item being added.
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:param value: Value to store
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:return:
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"""
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LOG.debug("Updating item '%(item)s' in cache '%(name)s'",
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{'item': key,
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'name': self.name})
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self.cache[key] = {'date': timeutils.utcnow(),
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'value': value}
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def get_value(self, key):
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"""Returns an item from the cache
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:param key: Key for the item being requested.
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:return: Value of item or None if doesn't exist or expired
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"""
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value = self._validate(key)
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if value is None:
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LOG.debug("Item '%(item)s' is not in cache '%(name)s' ",
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{'item': key,
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'name': self.name})
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return value
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