52 lines
1.7 KiB
Python
52 lines
1.7 KiB
Python
from typing import Any, Protocol
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class CacheClient(Protocol):
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async def get(self, key: str) -> Any: ...
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async def set(self, key: str, value: str, ex: int | None = None) -> Any: ...
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class CacheReadResult:
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def __init__(self, value: Any, degraded: bool = False) -> None:
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self.value = value
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self.degraded = degraded
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class MemoryCacheAdapter:
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"""Cache is an optimization; failures must not block MySQL recall."""
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def __init__(self, client: CacheClient) -> None:
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self.client = client
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async def get(self, key: str) -> CacheReadResult:
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try:
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return CacheReadResult(await self.client.get(key))
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except Exception:
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return CacheReadResult(None, degraded=True)
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async def set(self, key: str, value: str, ttl_seconds: int = 300) -> bool:
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try:
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await self.client.set(key, value, ex=ttl_seconds)
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return True
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except Exception:
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return False
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async def delete(self, *keys: str) -> int:
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"""删除若干缓存键；客户端不支持删除时返回 0，缓存只是可重建的优化层。
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记忆热缓存按客户维度失效，失效失败不得阻塞主流程，因此这里吞掉异常，
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由调用方通过返回值与 `degraded` 语义决定是否告警。
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"""
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targets = [key for key in keys if key]
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if not targets:
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return 0
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delete = getattr(self.client, "delete", None)
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if delete is None:
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return 0
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try:
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removed = await delete(*targets)
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except Exception:
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return 0
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return int(removed) if isinstance(removed, int) else len(targets)
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