Add function description

src/tribler/core/utilities/pony_utils.py

@@ -34,7 +34,7 @@ def get_max(cls: Type[Entity], column_name='rowid') -> int:
 
 
 async def run_threaded(db: Database, func: Callable, *args, **kwargs):
- """ Run `func` threaded and close DB connection at the end of the execution.
+ """Run `func` threaded and close DB connection at the end of the execution.
 
  Args:
  db: the DB to be closed
@@ -43,6 +43,15 @@ async def run_threaded(db: Database, func: Callable, *args, **kwargs):
  **kwargs: kwargs for the function call
 
  Returns: a result of the func call.
+
+ You should use `run_threaded` to wrap all functions that should be executed from a separate thread and work with
+ the database. The `run_threaded` function ensures that all database connections opened in worker threads are
+ properly closed before the Tribler shutdown.
+
+ The Asyncio `run_in_executor` method executes its argument in a separate worker thread. After the db_session is
+ over, PonyORM caches the connection to the database to re-use it again later in the same thread. It was previously
+ reported that some obscure problems could be observed during the Tribler shutdown if connections in the Tribler
+ worker threads are not closed properly.
  """
 
  def wrapper():