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proxystore.utils.tasks

Safely spawn asyncio background tasks with error handling.

SafeTaskExitError

Bases: Exception

Exception that can be raised inside a task to safely exit it.

exit_on_error 

exit_on_error(task: Task[Any]) -> None

Task callback that raises SystemExit on task exception.

Source code in proxystore/utils/tasks.py 
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def exit_on_error(task: asyncio.Task[Any]) -> None:
    """Task callback that raises SystemExit on task exception."""
    if (
        not task.cancelled()
        and task.exception() is not None
        and not isinstance(task.exception(), SafeTaskExitError)
    ):
        logger.error(
            f'Exception in background task (name="{task.get_name()}"): '
            f'{task.exception()!r}',
        )
        raise SystemExit(1)

spawn_guarded_background_task 

spawn_guarded_background_task(
    coro: Callable[..., Coroutine[Any, Any, None]],
    *args: Any,
    **kwargs: Any
) -> Task[Any]

Run a coroutine safely in the background.

Launches the coroutine as an asyncio task and sets the done callback to exit_on_error(). This is "safe" because it will ensure exceptions inside the task get logged and cause the program to exit. Otherwise, background tasks that are not awaited may not have their exceptions raised such that programs hang with no notice of the exception that caused the hang.

Tasks can raise SafeTaskExit to signal the task is finished but should not cause a system exit.

Source: https://stackoverflow.com/questions/62588076

Parameters:

  • coro (Callable[..., Coroutine[Any, Any, None]]) –

    Coroutine to run as task.

  • args (Any, default: () ) –

    Positional arguments for the coroutine.

  • kwargs (Any, default: {} ) –

    Keyword arguments for the coroutine.

Returns:

  • Task[Any] –

    Asyncio task handle.

Source code in proxystore/utils/tasks.py 
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def spawn_guarded_background_task(
    coro: Callable[..., Coroutine[Any, Any, None]],
    *args: Any,
    **kwargs: Any,
) -> asyncio.Task[Any]:
    """Run a coroutine safely in the background.

    Launches the coroutine as an asyncio task and sets the done
    callback to [`exit_on_error()`][proxystore.utils.tasks.exit_on_error].
    This is "safe" because it will ensure exceptions inside the task get logged
    and cause the program to exit. Otherwise, background tasks that are not
    awaited may not have their exceptions raised such that programs hang with
    no notice of the exception that caused the hang.

    Tasks can raise [`SafeTaskExit`][proxystore.utils.tasks.SafeTaskExitError]
    to signal the task is finished but should not cause a system exit.

    Source: https://stackoverflow.com/questions/62588076

    Args:
        coro: Coroutine to run as task.
        args: Positional arguments for the coroutine.
        kwargs: Keyword arguments for the coroutine.

    Returns:
        Asyncio task handle.
    """
    task = asyncio.create_task(
        _execute_and_log_traceback(coro, *args, **kwargs),
    )
    task.add_done_callback(exit_on_error)
    return task