Add voice analytics filters and metrics

backend/app/db/database.py

@@ -6,7 +6,7 @@ from app.core.config import settings
 
 _engine = None
 _session_factory: async_sessionmaker[AsyncSession] | None = None
-_lock = threading.Lock()
+_lock = threading.RLock()
 
 
 def _get_engine():
@@ -34,6 +34,25 @@ def _get_session_factory():
     return _session_factory
 
 
+async def dispose_engine():
+    """Dispose the async engine and reset cached DB handles.
+
+    Celery tasks run async code through ``asyncio.run()``, which creates and closes
+    one event loop per task. Asyncpg connections are bound to the loop that created
+    them, so worker tasks must not keep pooled connections across task runs.
+    """
+    global _engine, _session_factory
+
+    engine = _engine
+    if engine is not None:
+        await engine.dispose()
+
+    with _lock:
+        if _engine is engine:
+            _engine = None
+            _session_factory = None
+
+
 async def init_db():
     """Create tables if they do not exist."""
     from app.db.models import Base  # main models