mode.utils.futures
¶
Async I/O Future utilities.
- mode.utils.futures.done_future(result: Optional[Any] = None, *, loop: Optional[AbstractEventLoop] = None) Future ¶
Return
asyncio.Future
that is already evaluated.
- async mode.utils.futures.maybe_async(res: Any) Any ¶
Await future if argument is Awaitable.
Examples
>>> await maybe_async(regular_function(arg)) >>> await maybe_async(async_function(arg))
- mode.utils.futures.maybe_cancel(fut: _asyncio.Future | None) bool ¶
Cancel future if it is cancellable.
- mode.utils.futures.maybe_set_exception(fut: _asyncio.Future | None, exc: BaseException) bool ¶
Set future exception if not already done.
- mode.utils.futures.maybe_set_result(fut: _asyncio.Future | None, result: Any) bool ¶
Set future result if not already done.
- mode.utils.futures.notify(fut: _asyncio.Future | None, result: Optional[Any] = None) None ¶
Set
asyncio.Future
result if future exists and is not done.
- class mode.utils.futures.stampede(fget: Callable, *, doc: Optional[str] = None)¶
Descriptor for cached async operations providing stampede protection.
See also thundering herd problem.
Adding the decorator to an async callable method:
Examples
Here’s an example coroutine method connecting a network client:
class Client: @stampede async def maybe_connect(self): await self._connect() async def _connect(self): return Connection()
In the above example, if multiple coroutines call
maybe_connect
at the same time, then only one of them will actually perform the operation. The rest of the coroutines will wait for the result, and return it once the first caller returns.