145 lines
4.1 KiB
Python
145 lines
4.1 KiB
Python
"Thread-safe in-memory cache backend."
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import time
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try:
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import cPickle as pickle
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except ImportError:
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import pickle
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from django.core.cache.backends.base import BaseCache
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from django.utils.synch import RWLock
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# Global in-memory store of cache data. Keyed by name, to provide
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# multiple named local memory caches.
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_caches = {}
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_expire_info = {}
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_locks = {}
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class LocMemCache(BaseCache):
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def __init__(self, name, params):
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BaseCache.__init__(self, params)
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global _caches, _expire_info, _locks
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self._cache = _caches.setdefault(name, {})
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self._expire_info = _expire_info.setdefault(name, {})
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self._lock = _locks.setdefault(name, RWLock())
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def add(self, key, value, timeout=None, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.writer_enters()
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try:
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exp = self._expire_info.get(key)
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if exp is None or exp <= time.time():
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try:
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self._set(key, pickle.dumps(value), timeout)
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return True
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except pickle.PickleError:
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pass
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return False
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finally:
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self._lock.writer_leaves()
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def get(self, key, default=None, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.reader_enters()
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try:
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exp = self._expire_info.get(key)
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if exp is None:
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return default
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elif exp > time.time():
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try:
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return pickle.loads(self._cache[key])
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except pickle.PickleError:
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return default
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finally:
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self._lock.reader_leaves()
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self._lock.writer_enters()
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try:
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try:
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del self._cache[key]
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del self._expire_info[key]
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except KeyError:
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pass
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return default
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finally:
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self._lock.writer_leaves()
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def _set(self, key, value, timeout=None):
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if len(self._cache) >= self._max_entries:
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self._cull()
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if timeout is None:
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timeout = self.default_timeout
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self._cache[key] = value
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self._expire_info[key] = time.time() + timeout
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def set(self, key, value, timeout=None, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.writer_enters()
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try:
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self._set(key, pickle.dumps(value), timeout)
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except pickle.PickleError:
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pass
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finally:
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self._lock.writer_leaves()
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def has_key(self, key, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.reader_enters()
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try:
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exp = self._expire_info.get(key)
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if exp is None:
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return False
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elif exp > time.time():
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return True
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finally:
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self._lock.reader_leaves()
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self._lock.writer_enters()
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try:
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try:
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del self._cache[key]
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del self._expire_info[key]
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except KeyError:
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pass
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return False
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finally:
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self._lock.writer_leaves()
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def _cull(self):
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if self._cull_frequency == 0:
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self.clear()
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else:
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doomed = [k for (i, k) in enumerate(self._cache) if i % self._cull_frequency == 0]
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for k in doomed:
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self._delete(k)
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def _delete(self, key):
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try:
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del self._cache[key]
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except KeyError:
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pass
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try:
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del self._expire_info[key]
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except KeyError:
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pass
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def delete(self, key, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.writer_enters()
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try:
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self._delete(key)
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finally:
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self._lock.writer_leaves()
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def clear(self):
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self._cache.clear()
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self._expire_info.clear()
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# For backwards compatibility
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class CacheClass(LocMemCache):
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pass
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