118 lines
3.9 KiB
Python
118 lines
3.9 KiB
Python
"Thread-safe in-memory cache backend."
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import pickle
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import time
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from collections import OrderedDict
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from threading import Lock
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from django.core.cache.backends.base import DEFAULT_TIMEOUT, BaseCache
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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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pickle_protocol = pickle.HIGHEST_PROTOCOL
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def __init__(self, name, params):
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super().__init__(params)
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self._cache = _caches.setdefault(name, OrderedDict())
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self._expire_info = _expire_info.setdefault(name, {})
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self._lock = _locks.setdefault(name, Lock())
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def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
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key = self.make_and_validate_key(key, version=version)
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pickled = pickle.dumps(value, self.pickle_protocol)
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with self._lock:
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if self._has_expired(key):
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self._set(key, pickled, timeout)
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return True
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return False
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def get(self, key, default=None, version=None):
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key = self.make_and_validate_key(key, version=version)
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with self._lock:
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if self._has_expired(key):
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self._delete(key)
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return default
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pickled = self._cache[key]
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self._cache.move_to_end(key, last=False)
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return pickle.loads(pickled)
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def _set(self, key, value, timeout=DEFAULT_TIMEOUT):
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if len(self._cache) >= self._max_entries:
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self._cull()
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self._cache[key] = value
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self._cache.move_to_end(key, last=False)
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self._expire_info[key] = self.get_backend_timeout(timeout)
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def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
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key = self.make_and_validate_key(key, version=version)
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pickled = pickle.dumps(value, self.pickle_protocol)
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with self._lock:
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self._set(key, pickled, timeout)
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def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
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key = self.make_and_validate_key(key, version=version)
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with self._lock:
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if self._has_expired(key):
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return False
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self._expire_info[key] = self.get_backend_timeout(timeout)
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return True
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def incr(self, key, delta=1, version=None):
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key = self.make_and_validate_key(key, version=version)
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with self._lock:
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if self._has_expired(key):
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self._delete(key)
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raise ValueError("Key '%s' not found" % key)
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pickled = self._cache[key]
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value = pickle.loads(pickled)
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new_value = value + delta
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pickled = pickle.dumps(new_value, self.pickle_protocol)
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self._cache[key] = pickled
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self._cache.move_to_end(key, last=False)
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return new_value
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def has_key(self, key, version=None):
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key = self.make_and_validate_key(key, version=version)
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with self._lock:
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if self._has_expired(key):
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self._delete(key)
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return False
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return True
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def _has_expired(self, key):
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exp = self._expire_info.get(key, -1)
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return exp is not None and exp <= time.time()
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def _cull(self):
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if self._cull_frequency == 0:
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self._cache.clear()
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self._expire_info.clear()
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else:
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count = len(self._cache) // self._cull_frequency
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for i in range(count):
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key, _ = self._cache.popitem()
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del self._expire_info[key]
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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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del self._expire_info[key]
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except KeyError:
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return False
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return True
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def delete(self, key, version=None):
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key = self.make_and_validate_key(key, version=version)
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with self._lock:
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return self._delete(key)
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def clear(self):
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with self._lock:
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self._cache.clear()
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self._expire_info.clear()
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