update

devplacepy_services/base/cache.py

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