131 lines
4.2 KiB
Python
131 lines
4.2 KiB
Python
# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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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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"""Simple wrapper for oslo_cache."""
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from oslo_cache import core as cache
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from oslo_log import log as logging
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import nova.conf
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from nova.i18n import _
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CONF = nova.conf.CONF
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LOG = logging.getLogger(__name__)
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WEEK = 604800
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def _warn_if_null_backend():
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if CONF.cache.backend == 'dogpile.cache.null':
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LOG.warning("Cache enabled with backend dogpile.cache.null.")
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def get_memcached_client(expiration_time=0):
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"""Used ONLY when memcached is explicitly needed."""
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# If the operator has [cache]/enabled flag on then we let oslo_cache
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# configure the region from the configuration settings
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if CONF.cache.enabled and CONF.cache.memcache_servers:
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_warn_if_null_backend()
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return CacheClient(
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_get_default_cache_region(expiration_time=expiration_time))
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def get_client(expiration_time=0):
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"""Used to get a caching client."""
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# If the operator has [cache]/enabled flag on then we let oslo_cache
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# configure the region from configuration settings.
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if CONF.cache.enabled:
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_warn_if_null_backend()
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return CacheClient(
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_get_default_cache_region(expiration_time=expiration_time))
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# If [cache]/enabled flag is off, we use the dictionary backend
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return CacheClient(
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_get_custom_cache_region(expiration_time=expiration_time,
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backend='oslo_cache.dict'))
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def _get_default_cache_region(expiration_time):
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region = cache.create_region()
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if expiration_time != 0:
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CONF.cache.expiration_time = expiration_time
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cache.configure_cache_region(CONF, region)
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return region
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def _get_custom_cache_region(expiration_time=WEEK,
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backend=None,
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url=None):
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"""Create instance of oslo_cache client.
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For backends you can pass specific parameters by kwargs.
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For 'dogpile.cache.memcached' backend 'url' parameter must be specified.
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:param backend: backend name
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:param expiration_time: interval in seconds to indicate maximum
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time-to-live value for each key
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:param url: memcached url(s)
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"""
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region = cache.create_region()
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region_params = {}
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if expiration_time != 0:
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region_params['expiration_time'] = expiration_time
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if backend == 'oslo_cache.dict':
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region_params['arguments'] = {'expiration_time': expiration_time}
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elif backend == 'dogpile.cache.memcached':
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region_params['arguments'] = {'url': url}
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else:
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raise RuntimeError(_('old style configuration can use '
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'only dictionary or memcached backends'))
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region.configure(backend, **region_params)
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return region
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class CacheClient(object):
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"""Replicates a tiny subset of memcached client interface."""
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def __init__(self, region):
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self.region = region
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def get(self, key):
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value = self.region.get(key)
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if value == cache.NO_VALUE:
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return None
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return value
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def get_or_create(self, key, creator):
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return self.region.get_or_create(key, creator)
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def set(self, key, value):
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return self.region.set(key, value)
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def add(self, key, value):
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return self.region.get_or_create(key, lambda: value)
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def delete(self, key):
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return self.region.delete(key)
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def get_multi(self, keys):
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values = self.region.get_multi(keys)
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return [None if value is cache.NO_VALUE else value for value in
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values]
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def delete_multi(self, keys):
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return self.region.delete_multi(keys)
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