105 lines
3.4 KiB
Python
105 lines
3.4 KiB
Python
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import typing as _t
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from time import time
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from cachelib.base import BaseCache
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from cachelib.serializers import SimpleSerializer
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class SimpleCache(BaseCache):
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"""Simple memory cache for single process environments. This class exists
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mainly for the development server and is not 100% thread safe. It tries
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to use as many atomic operations as possible and no locks for simplicity
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but it could happen under heavy load that keys are added multiple times.
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:param threshold: the maximum number of items the cache stores before
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it starts deleting some.
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:param default_timeout: the default timeout that is used if no timeout is
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specified on :meth:`~BaseCache.set`. A timeout of
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0 indicates that the cache never expires.
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"""
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serializer = SimpleSerializer()
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def __init__(
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self,
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threshold: int = 500,
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default_timeout: int = 300,
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):
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BaseCache.__init__(self, default_timeout)
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self._cache: _t.Dict[str, _t.Any] = {}
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self._threshold = threshold or 500 # threshold = 0
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def _over_threshold(self) -> bool:
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return len(self._cache) > self._threshold
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def _remove_expired(self, now: float) -> None:
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toremove = [k for k, (expires, _) in self._cache.items() if expires < now]
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for k in toremove:
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self._cache.pop(k, None)
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def _remove_older(self) -> None:
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k_ordered = (
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k
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for k, v in sorted(
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self._cache.items(), key=lambda item: item[1][0] # type: ignore
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)
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)
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for k in k_ordered:
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self._cache.pop(k, None)
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if not self._over_threshold():
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break
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def _prune(self) -> None:
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if self._over_threshold():
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now = time()
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self._remove_expired(now)
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# remove older items if still over threshold
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if self._over_threshold():
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self._remove_older()
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def _normalize_timeout(self, timeout: _t.Optional[int]) -> int:
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timeout = BaseCache._normalize_timeout(self, timeout)
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if timeout > 0:
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timeout = int(time()) + timeout
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return timeout
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def get(self, key: str) -> _t.Any:
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try:
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expires, value = self._cache[key]
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if expires == 0 or expires > time():
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return self.serializer.loads(value)
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except KeyError:
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return None
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def set(
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self, key: str, value: _t.Any, timeout: _t.Optional[int] = None
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) -> _t.Optional[bool]:
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expires = self._normalize_timeout(timeout)
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self._prune()
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self._cache[key] = (expires, self.serializer.dumps(value))
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return True
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def add(self, key: str, value: _t.Any, timeout: _t.Optional[int] = None) -> bool:
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expires = self._normalize_timeout(timeout)
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self._prune()
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item = (expires, self.serializer.dumps(value))
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if key in self._cache:
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return False
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self._cache.setdefault(key, item)
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return True
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def delete(self, key: str) -> bool:
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return self._cache.pop(key, None) is not None
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def has(self, key: str) -> bool:
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try:
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expires, value = self._cache[key]
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return bool(expires == 0 or expires > time())
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except KeyError:
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return False
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def clear(self) -> bool:
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self._cache.clear()
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return not bool(self._cache)
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