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Fix blocking issue in Voila (nbclient case) #1059

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Fix blocking issue in Voila (nbclient case) #1059

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4 changes: 0 additions & 4 deletions jupyter_client/session.py
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Original file line number Diff line number Diff line change
Expand Up @@ -810,10 +810,6 @@ def send(
# ZMQStreams and dummy sockets do not support tracking.
track = False

if isinstance(stream, zmq.asyncio.Socket):
assert stream is not None # type:ignore[unreachable]
stream = zmq.Socket.shadow(stream.underlying)
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without this, it's not actually guaranteed the send will happen, since it's not awaited (zmq.asyncio does currently immediately schedule sends, but it doesn't guarantee that it will continue to do so), and the type of tracker will be incorrect Awaitable[Event] instead of Event (and a different type when copy=True vs copy=False.

We could add async polling, either here or (perhaps easier) in nbclient, so you can avoid calling this when it would block:

events = await async_socket.poll(timeout_ms, zmq.POLLOUT)
if events & zmq.POLLOUT:
    session.send(async_socket) # won't block
else:
    # ????

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@JohanMabille JohanMabille Apr 23, 2025 •
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I might be missing some bits here, but would it be possible to handle that in the AsyncZMQSocketChannel instead? I.e. overwrite the send method, do the proper stuff, and then call session.send? This would prevent the Socket wrapper from leaking into the Session class.

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Yeah, that's probably where it belongs


if isinstance(msg_or_type, (Message, dict)):
# We got a Message or message dict, not a msg_type so don't
# build a new Message.
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