Initial commit

app/inbox_locks.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+import threading
+from dataclasses import dataclass
+
+
+@dataclass
+class InboxRunLease:
+    inbox_id: str
+    _lock: threading.Lock
+    _released: bool = False
+
+    def release(self) -> None:
+        if not self._released:
+            self._released = True
+            self._lock.release()
+
+    def __enter__(self) -> "InboxRunLease":
+        return self
+
+    def __exit__(self, exc_type, exc, tb) -> None:
+        self.release()
+
+
+class InboxRunLocks:
+    def __init__(self) -> None:
+        self._guard = threading.Lock()
+        self._locks: dict[str, threading.Lock] = {}
+
+    def acquire(self, inbox_id: str, *, blocking: bool = False) -> InboxRunLease | None:
+        with self._guard:
+            lock = self._locks.setdefault(inbox_id, threading.Lock())
+        if not lock.acquire(blocking=blocking):
+            return None
+        return InboxRunLease(inbox_id=inbox_id, _lock=lock)
+
+    def active(self, inbox_id: str) -> bool:
+        lease = self.acquire(inbox_id, blocking=False)
+        if not lease:
+            return True
+        lease.release()
+        return False
+
+
+inbox_run_locks = InboxRunLocks()