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.
Jonathan
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 <ba...@barrys-emacs.org> a
écrit :
>
>
> > On 25 Feb 2021, at 13:14, Yves Duprat <ydup...@gmail.com> wrote:
> >
> > Hi,the list,
> >
> > 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.
>
> Barry
>
>
>
> >
> > Yves
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