67 lines
2.1 KiB
Python
67 lines
2.1 KiB
Python
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# retoor <retoor@molodetz.nl>
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from __future__ import annotations
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import time
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from collections import OrderedDict
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class TTLCache:
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def __init__(self, ttl: int, max_size: int = 0):
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self.ttl = ttl
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self.max_size = max_size
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self._store: OrderedDict[str, tuple[object, float]] = OrderedDict()
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def get(self, key: str):
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entry = self._store.get(key)
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if entry is None:
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return None
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value, expiry = entry
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if time.time() >= expiry:
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self._store.pop(key, None)
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return None
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self._store.move_to_end(key)
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return value
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def set(self, key: str, value) -> None:
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self._store[key] = (value, time.time() + self.ttl)
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self._store.move_to_end(key)
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if self.max_size and len(self._store) > self.max_size:
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self._store.popitem(last=False)
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def pop(self, key: str) -> None:
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self._store.pop(key, None)
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def clear(self) -> None:
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self._store.clear()
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class CacheStateGate:
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def __init__(self, *, ttl: int = 60, max_staleness: float = 5.0):
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self.ttl = ttl
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self.max_staleness = max_staleness
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self._cache = TTLCache(ttl=ttl)
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self._versions: dict[str, int] = {}
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self._bumped_at: dict[str, float] = {}
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def get_version(self, name: str) -> int:
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return int(self._versions.get(name, 0))
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def bump(self, name: str) -> int:
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next_version = self.get_version(name) + 1
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self._versions[name] = next_version
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self._bumped_at[name] = time.time()
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self._cache.clear()
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return next_version
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def get(self, key: str, version_name: str, loader):
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bumped_at = self._bumped_at.get(version_name, 0.0)
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if bumped_at and (time.time() - bumped_at) < self.max_staleness:
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self._cache.pop(key)
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version_key = f"{version_name}:{self.get_version(version_name)}"
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cached = self._cache.get(version_key)
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if cached is not None:
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return cached
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value = loader()
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self._cache.set(version_key, value)
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return value
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