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# Copyright 2016 Mirantis, 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 logging
import threading
import time
from oslo_messaging._drivers.zmq_driver import zmq_async
LOG = logging.getLogger(__name__)
zmq = zmq_async.import_zmq()
class TTLCache(object):
_UNDEFINED = object()
def __init__(self, ttl=None):
self._lock = threading.Lock()
self._cache = {}
self._executor = None
if not (ttl is None or isinstance(ttl, (int, float))):
raise ValueError('ttl must be None or a number')
# no (i.e. infinite) ttl
if ttl is None or ttl <= 0:
ttl = float('inf')
else:
self._executor = zmq_async.get_executor(self._update_cache)
self._ttl = ttl
if self._executor:
self._executor.execute()
@staticmethod
def _is_expired(expiration_time, current_time):
return expiration_time <= current_time
def add(self, key, value=None):
with self._lock:
expiration_time = time.time() + self._ttl
self._cache[key] = (value, expiration_time)
def get(self, key, default=None):
with self._lock:
data = self._cache.get(key)
if data is None:
return default
value, expiration_time = data
if self._is_expired(expiration_time, time.time()):
del self._cache[key]
return default
return value
def __contains__(self, key):
return self.get(key, self._UNDEFINED) is not self._UNDEFINED
def _update_cache(self):
with self._lock:
current_time = time.time()
old_size = len(self._cache)
self._cache = \
{key: (value, expiration_time) for
key, (value, expiration_time) in self._cache.items()
if not self._is_expired(expiration_time, current_time)}
new_size = len(self._cache)
LOG.debug('Updated cache: current size %(new_size)s '
'(%(size_difference)s records removed)',
{'new_size': new_size,
'size_difference': old_size - new_size})
time.sleep(self._ttl)
def cleanup(self):
if self._executor:
self._executor.stop()
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