Initial Commit

app/owuitools/cache.py

@@ -0,0 +1,85 @@
+"""Response cache.
+
+Not a performance nicety. Stack Exchange allows 300 calls/day/IP without a
+key and GitHub 60/hour, and those budgets are shared by every user of the
+assistant at once. Without caching, two people comparing package versions
+can spend the day's quota before lunch and every later answer degrades to
+"I couldn't check" - or worse, to the model guessing.
+
+Fails open: if valkey is unreachable the tools still work, they are just
+uncached. A dead cache should never take the assistant's tools with it.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import logging
+
+import redis.asyncio as redis
+
+from .settings import settings
+
+log = logging.getLogger(__name__)
+
+_pool: redis.Redis | None = None
+
+# Chosen per-source from how fast the underlying thing actually changes.
+TTL = {
+    "search": 900,          # 15m - fresh enough for "latest", cheap to redo
+    "page": 3600,           # 1h  - article text rarely changes within a session
+    "wikipedia": 21600,     # 6h
+    "stackexchange": 21600, # 6h  - 300/day keyless makes this the tightest budget
+    "rfc": 604800,          # 7d  - a published RFC is immutable
+    "man": 604800,          # 7d
+    "cve": 10800,           # 3h  - CVSS scores do get revised
+    "package": 3600,        # 1h  - the whole point is catching a new release
+    "rdap": 86400,          # 24h
+    "dns": 300,             # 5m  - short on purpose; people debug live changes
+    "tls": 1800,            # 30m
+    "papers": 86400,        # 24h
+    "datasheet": 604800,    # 7d
+}
+
+
+def _key(namespace: str, *parts: str) -> str:
+    digest = hashlib.sha256("\x1f".join(parts).encode()).hexdigest()[:32]
+    return f"owuitools:{namespace}:{digest}"
+
+
+async def get_redis() -> redis.Redis | None:
+    global _pool
+    if _pool is None:
+        try:
+            _pool = redis.from_url(settings.valkey_url, decode_responses=True, socket_timeout=2)
+            await _pool.ping()
+        except Exception as exc:
+            log.warning("cache unavailable, continuing without it: %s", exc)
+            _pool = None
+    return _pool
+
+
+async def close_redis() -> None:
+    global _pool
+    if _pool is not None:
+        await _pool.aclose()
+        _pool = None
+
+
+async def cached(namespace: str, *parts: str) -> str | None:
+    client = await get_redis()
+    if client is None:
+        return None
+    try:
+        return await client.get(_key(namespace, *parts))
+    except Exception:
+        return None
+
+
+async def store(namespace: str, value: str, *parts: str) -> None:
+    client = await get_redis()
+    if client is None:
+        return
+    try:
+        await client.setex(_key(namespace, *parts), TTL.get(namespace, 3600), value)
+    except Exception as exc:
+        log.debug("cache write failed for %s: %s", namespace, exc)