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OpenStack Study: memorycache.py**** CubicPower OpenStack Study ****
# vim: tabstop=4 shiftwidth=4 softtabstop=4 # 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.""" from oslo.config import cfg from nova.openstack.common import timeutils memcache_opts = [ cfg.ListOpt('memcached_servers', default=None, help='Memcached servers or None for in process cache.'), ] CONF = cfg.CONF CONF.register_opts(memcache_opts)
**** CubicPower OpenStack Study **** def get_client(memcached_servers=None): client_cls = Client if not memcached_servers: memcached_servers = CONF.memcached_servers if memcached_servers: try: import memcache client_cls = memcache.Client except ImportError: pass return client_cls(memcached_servers, debug=0)
**** CubicPower OpenStack Study **** class Client(object): """Replicates a tiny subset of memcached client interface."""
**** CubicPower OpenStack Study **** def __init__(self, *args, **kwargs): """Ignores the passed in args.""" self.cache = {}
**** CubicPower OpenStack Study **** def get(self, key): """Retrieves the value for a key or None. This expunges expired keys during each get. """ now = timeutils.utcnow_ts() for k in self.cache.keys(): (timeout, _value) = self.cache[k] if timeout and now >= timeout: del self.cache[k] return self.cache.get(key, (0, None))[1]
**** CubicPower OpenStack Study **** def set(self, key, value, time=0, min_compress_len=0): """Sets the value for a key.""" timeout = 0 if time != 0: timeout = timeutils.utcnow_ts() + time self.cache[key] = (timeout, value) return True
**** CubicPower OpenStack Study **** def add(self, key, value, time=0, min_compress_len=0): """Sets the value for a key if it doesn't exist.""" if self.get(key) is not None: return False return self.set(key, value, time, min_compress_len)
**** CubicPower OpenStack Study **** def incr(self, key, delta=1): """Increments the value for a key.""" value = self.get(key) if value is None: return None new_value = int(value) + delta self.cache[key] = (self.cache[key][0], str(new_value)) return new_value
**** CubicPower OpenStack Study **** def delete(self, key, time=0): """Deletes the value associated with a key.""" if key in self.cache: del self.cache[key]
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