def __init__(self, threshold=500, default_timeout=300, pickle=True):
BaseCache.__init__(self, default_timeout)
self._cache = {}
self._threshold = threshold
self._pickle = pickle
self._lock = RWLock()
class SafeSimpleCache(BaseCache):
"""Simple memory cache for multi process environments.
:param threshold: the maximum number of items the cache stores before
it starts deleting some.
:param default_timeout: the default timeout that is used if no timeout is
specified on :meth:`~BaseCache.set`.
:param pickle: Allows disabling of automatic pickle action if you're just
storing basic python objects.
"""
def __init__(self, threshold=500, default_timeout=300, pickle=True):
BaseCache.__init__(self, default_timeout)
self._cache = {}
self._threshold = threshold
self._pickle = pickle
self._lock = RWLock()
def _serial(self, val):
if self._pickle:
return pickle.dumps(val, pickle.HIGHEST_PROTOCOL)
return val
def _deserial(self, val):
if self._pickle:
return pickle.loads(val)
return val
def clear(self):
with self._lock.writer():
self._cache.clear()
return True
def _prune(self):
with self._lock.reader():
length = len(self._cache)
if length > self._threshold:
now = time()
with self._lock.writer():
for idx, (key, (expires, _)) in enumerate(self._cache.items()):
if expires <= now or idx % 3 == 0:
self._cache.pop(key, None)
def get(self, key):
try:
with self._lock.reader():
expires, value = self._cache[key]
if expires > time():
return self._deserial(value)
except (KeyError, pickle.PickleError):
return None
def set(self, key, value, timeout=None):
if timeout is None:
timeout = self.default_timeout
self._prune()
new_key = (time() + timeout, self._serial(value))
with self._lock.writer():
self._cache[key] = new_key
return True
def add(self, key, value, timeout=None):
if timeout is None:
timeout = self.default_timeout
self._prune()
with self._lock.reader():
if key in self._cache:
return False
item = (time() + timeout, self._serial(value))
with self._lock.writer():
self._cache.setdefault(key, item)
return True
def delete(self, key):
with self._lock.writer():
return self._cache.pop(key, None) is not None
