621693ecc8
The inline dict cache was a latent bug: no lock (the engine singleton is hit by concurrent Flask + worker threads) and a wholesale-clear cliff at 256 (nuked hot entries). Extracted a thread-safe TTL+LRU TTLCache into an importable core/ module with seam tests (expiry via injected clock, LRU-not-wholesale eviction, a concurrency stress test). Engine now uses it; search is cached too (60s, ownership re-stamped fresh). Deliberately NOT persisted to disk — durable data already lives in video.db; that tier would be over-engineering for a self-hosted app.
50 lines
1.8 KiB
Python
50 lines
1.8 KiB
Python
"""A small thread-safe TTL + LRU cache for the video enrichment engine.
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The engine is a process-wide singleton hit concurrently by Flask request threads
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AND the worker threads, so the cache must be locked. Entries expire after a TTL;
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when the cache is full the LEAST-RECENTLY-USED entry is evicted (not the whole
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cache wholesale). Isolated: imports only the stdlib; no music, no DB.
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"""
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from __future__ import annotations
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import threading
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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, maxsize: int = 256, ttl: float = 1800.0, clock=time.monotonic):
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self._max = max(1, int(maxsize))
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self._ttl = float(ttl)
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self._clock = clock # injectable for tests
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self._lock = threading.Lock()
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self._data: OrderedDict = OrderedDict() # key -> (expires_at, value)
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def get(self, key):
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now = self._clock()
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with self._lock:
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hit = self._data.get(key)
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if hit is None:
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return None
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if hit[0] <= now: # expired
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del self._data[key]
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return None
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self._data.move_to_end(key) # mark recently used
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return hit[1]
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def put(self, key, value, ttl: float | None = None) -> None:
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expires_at = self._clock() + (self._ttl if ttl is None else float(ttl))
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with self._lock:
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self._data[key] = (expires_at, value)
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self._data.move_to_end(key)
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while len(self._data) > self._max: # evict LRU (oldest), not everything
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self._data.popitem(last=False)
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def clear(self) -> None:
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with self._lock:
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self._data.clear()
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def __len__(self) -> int:
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with self._lock:
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return len(self._data)
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