refine db connection (#1494)

### What problem does this PR solve?



### Type of change


- [x] Refactoring

api/db/db_models.py

@@ -332,7 +332,7 @@ DB.lock = DatabaseLock
 def close_connection():
     try:
         if DB:
-            DB.close()
+            DB.close_stale(age=30)
     except Exception as e:
         LOGGER.exception(e)