It does make sense to have a barrier synchronization primitive for asyncio. The idea is to make a coroutine block until at least X coroutines are waiting to enter the barrier. This is very useful, if certain actions need to be synchronized.
Recently, I had to implement a barier myself for our use case. See code below:
It is simple to implement, but I too would like to have one for asyncio, in order to be consistent with the concurrency primitives we have for threading.
class Barier: """ Make a coroutine block until there are at least X waiters.
Similar to the threading Barier objects but for asyncio: https://docs.python.org/3/library/threading.html#barrier-objects """
def __init__(self, parties: int) -> None: self.parties = parties self._waiting: int self._event = asyncio.Event()
def add_one(self) -> None: self._waiting += 1 if self._waiting == self.parties: self._event.set()
async def wait(self, worker: "Worker") -> None: """ Wait until all we have at least `parties` waiters. """ self.add_one() await self._event.wait()
Le jeu. 25 févr. 2021 à 16:42, Barry Scott email@example.com a écrit :
On 25 Feb 2021, at 13:14, Yves Duprat firstname.lastname@example.org wrote:
I'm wondering why Barrier object does not exist in the synchronization
primitives of the asyncio lib while it is present in threading and multiprocessing libs ?
This may not be the right place to ask this question, but I never found
an answer on the web.
Thanks for your help.
I'm assuming that the barrier you are speaking of is the mechanism that is used to synchronise threads/processes running in parallel to prevent data races.
With async code that is never an issue. Each function runs to completion uninterrupted. There are no data races. Each time a async function runs it can know that the state of the objects it uses will not be changed while it is running.
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