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OpenStack Study: memory.py**** CubicPower OpenStack Study ****
# Copyright 2013 Red Hat, Inc. # # 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. import collections from neutron.openstack.common.cache import backends from neutron.openstack.common import lockutils from neutron.openstack.common import timeutils
**** CubicPower OpenStack Study **** class MemoryBackend(backends.BaseCache):
**** CubicPower OpenStack Study **** def __init__(self, parsed_url, options=None): super(MemoryBackend, self).__init__(parsed_url, options) self._clear()
**** CubicPower OpenStack Study **** def _set_unlocked(self, key, value, ttl=0): expires_at = 0 if ttl != 0: expires_at = timeutils.utcnow_ts() + ttl self._cache[key] = (expires_at, value) if expires_at: self._keys_expires[expires_at].add(key)
**** CubicPower OpenStack Study **** def _set(self, key, value, ttl=0, not_exists=False): with lockutils.lock(key): # NOTE(flaper87): This is needed just in `set` # calls, hence it's not in `_set_unlocked` if not_exists and self._exists_unlocked(key): return False self._set_unlocked(key, value, ttl) return True
**** CubicPower OpenStack Study **** def _get_unlocked(self, key, default=None): now = timeutils.utcnow_ts() try: timeout, value = self._cache[key] except KeyError: return (0, default) if timeout and now >= timeout: # NOTE(flaper87): Record expired, # remove it from the cache but catch # KeyError and ValueError in case # _purge_expired removed this key already. try: del self._cache[key] except KeyError: pass try: # NOTE(flaper87): Keys with ttl == 0 # don't exist in the _keys_expires dict self._keys_expires[timeout].remove(key) except (KeyError, ValueError): pass return (0, default) return (timeout, value)
**** CubicPower OpenStack Study **** def _get(self, key, default=None): with lockutils.lock(key): return self._get_unlocked(key, default)[1]
**** CubicPower OpenStack Study **** def _exists_unlocked(self, key): now = timeutils.utcnow_ts() try: timeout = self._cache[key][0] return not timeout or now <= timeout except KeyError: return False
**** CubicPower OpenStack Study **** def __contains__(self, key): with lockutils.lock(key): return self._exists_unlocked(key)
**** CubicPower OpenStack Study **** def _incr_append(self, key, other): with lockutils.lock(key): timeout, value = self._get_unlocked(key) if value is None: return None ttl = timeutils.utcnow_ts() - timeout new_value = value + other self._set_unlocked(key, new_value, ttl) return new_value
**** CubicPower OpenStack Study **** def _incr(self, key, delta): if not isinstance(delta, int): raise TypeError('delta must be an int instance') return self._incr_append(key, delta)
**** CubicPower OpenStack Study **** def _append_tail(self, key, tail): return self._incr_append(key, tail)
**** CubicPower OpenStack Study **** def _purge_expired(self): """Removes expired keys from the cache.""" now = timeutils.utcnow_ts() for timeout in sorted(self._keys_expires.keys()): # NOTE(flaper87): If timeout is greater # than `now`, stop the iteration, remaining # keys have not expired. if now < timeout: break # NOTE(flaper87): Unset every key in # this set from the cache if its timeout # is equal to `timeout`. (The key might # have been updated) for subkey in self._keys_expires.pop(timeout): try: if self._cache[subkey][0] == timeout: del self._cache[subkey] except KeyError: continue
**** CubicPower OpenStack Study **** def __delitem__(self, key): self._purge_expired() # NOTE(flaper87): Delete the key. Using pop # since it could have been deleted already value = self._cache.pop(key, None) if value: try: # NOTE(flaper87): Keys with ttl == 0 # don't exist in the _keys_expires dict self._keys_expires[value[0]].remove(value[1]) except (KeyError, ValueError): pass
**** CubicPower OpenStack Study **** def _clear(self): self._cache = {} self._keys_expires = collections.defaultdict(set)
**** CubicPower OpenStack Study **** def _get_many(self, keys, default): return super(MemoryBackend, self)._get_many(keys, default)
**** CubicPower OpenStack Study **** def _set_many(self, data, ttl=0): return super(MemoryBackend, self)._set_many(data, ttl)
**** CubicPower OpenStack Study **** def _unset_many(self, keys): return super(MemoryBackend, self)._unset_many(keys)
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