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# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""Super simple fake memcache client."""
import copy
from oslo_cache import core as cache
from oslo_config import cfg
from nova.i18n import _
# NOTE(dims): There are many copies of memcache_opts with memcached_servers
# in various projects as this used to be in a copy of memory_cache.py
# Since we are making a change in just our copy, oslo-config-generator fails
# with cfg.DuplicateOptError unless we override the comparison check
class _DeprecatedListOpt(cfg.ListOpt):
def __ne__(self, another):
self_dict = copy.deepcopy(vars(self))
another_dict = copy.deepcopy(vars(another))
self_dict.pop('help')
self_dict.pop('deprecated_for_removal')
another_dict.pop('help')
another_dict.pop('deprecated_for_removal')
return self_dict != another_dict
memcache_opts = [
_DeprecatedListOpt('memcached_servers',
help='DEPRECATED: Memcached servers or None for in '
'process cache. "memcached_servers" opt is '
'deprecated in Mitaka. In Newton release '
'oslo.cache config options should be used as '
'this option will be removed. Please add a '
'[cache] group in your nova.conf file and '
'add "enable" and "memcache_servers" option in '
'this section.',
deprecated_for_removal=True),
]
CONF = cfg.CONF
CONF.register_opts(memcache_opts)
WEEK = 604800
def list_opts():
"""Entry point for oslo-config-generator."""
return [(None, copy.deepcopy(memcache_opts))]
def get_memcached_client(expiration_time=0):
"""Used ONLY when memcached is explicitly needed."""
# If the operator uses the old style [DEFAULT]/memcached_servers
# then we just respect that setting
if CONF.memcached_servers:
return CacheClient(
_get_custom_cache_region(expiration_time=expiration_time,
backend='dogpile.cache.memcached',
url=CONF.memcached_servers))
# If the operator still uses the new style [cache]/memcache_servers
# and has [cache]/enabled flag on then we let oslo_cache configure
# the region from the configuration settings
elif CONF.cache.enabled and CONF.cache.memcache_servers:
return CacheClient(
_get_default_cache_region(expiration_time=expiration_time))
raise RuntimeError(_('memcached_servers not defined'))
def get_client(expiration_time=0):
"""Used to get a caching client."""
# If the operator still uses the old style [DEFAULT]/memcached_servers
# then we just respect that setting
if CONF.memcached_servers:
return CacheClient(
_get_custom_cache_region(expiration_time=expiration_time,
backend='dogpile.cache.memcached',
url=CONF.memcached_servers))
# If the operator has [cache]/enabled flag on then we let oslo_cache
# configure the region from configuration settings.
elif CONF.cache.enabled:
return CacheClient(
_get_default_cache_region(expiration_time=expiration_time))
# If [cache]/enabled flag is off and [DEFAULT]/memcached_servers is
# absent we use the dictionary backend
return CacheClient(
_get_custom_cache_region(expiration_time=expiration_time,
backend='oslo_cache.dict'))
def _get_default_cache_region(expiration_time):
region = cache.create_region()
if expiration_time != 0:
CONF.cache.expiration_time = expiration_time
cache.configure_cache_region(CONF, region)
return region
def _get_custom_cache_region(expiration_time=WEEK,
backend=None,
url=None):
"""Create instance of oslo_cache client.
For backends you can pass specific parameters by kwargs.
For 'dogpile.cache.memcached' backend 'url' parameter must be specified.
:param backend: backend name
:param expiration_time: interval in seconds to indicate maximum
time-to-live value for each key
:param url: memcached url(s)
"""
region = cache.create_region()
region_params = {}
if expiration_time != 0:
region_params['expiration_time'] = expiration_time
if backend == 'oslo_cache.dict':
region_params['arguments'] = {'expiration_time': expiration_time}
elif backend == 'dogpile.cache.memcached':
region_params['arguments'] = {'url': url}
else:
raise RuntimeError(_('old style configuration can use '
'only dictionary or memcached backends'))
region.configure(backend, **region_params)
return region
class CacheClient(object):
"""Replicates a tiny subset of memcached client interface."""
def __init__(self, region):
self.region = region
def get(self, key):
value = self.region.get(key)
if value == cache.NO_VALUE:
return None
return value
def get_or_create(self, key, creator):
return self.region.get_or_create(key, creator)
def set(self, key, value):
return self.region.set(key, value)
def add(self, key, value):
return self.region.get_or_create(key, lambda: value)
def delete(self, key):
return self.region.delete(key)
def get_multi(self, keys):
values = self.region.get_multi(keys)
return [None if value is cache.NO_VALUE else value for value in
values]
def delete_multi(self, keys):
return self.region.delete_multi(keys)
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