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Fix asyncio error when opening notebooks #6221

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merged 1 commit into from Nov 16, 2021
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dleen
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@dleen dleen commented Nov 3, 2021

This is a fix for #6164

nest_asyncio must be applied before any async tasks have been created
otherwise there could be tasks queued that are unpatched, and thus do
not respect nested loops. An example of an unpatched task can be seen in
the original issue:

<Task pending coro=<HTTP1ServerConnection._server_request_loop() running at /apps/python3/lib/python3.7/site-packages/tornado/http1connection.py:823>

which originates from Tornado.

A similar issue was reported in nest-asyncio: erdewit/nest_asyncio#22
where the solution is to call apply on import so that unpatched tasks
do not get created.

This is a fix for jupyter#6164

`nest_asyncio` must be applied before any async tasks have been created
otherwise there could be tasks queued that are unpatched, and thus do
not respect nested loops. An example of an unpatched task can be seen in
the original issue:

```
<Task pending coro=<HTTP1ServerConnection._server_request_loop() running at /apps/python3/lib/python3.7/site-packages/tornado/http1connection.py:823>
```
which originates from Tornado.

A similar issue was reported in `nest-asyncio`: erdewit/nest_asyncio#22
where the solution is to call `apply` on import so that unpatched tasks
do not get created.
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@kevin-bates kevin-bates left a comment

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These changes look good to me and I've confirmed the pending task error is not produced. Thank you.

I'd prefer to wait for another review prior to merging and have requested the help of others.

So we must call `nest_asyncio.apply()` method as early as possible. It
is preferable to do this in the consuming application rather than the
`jupyter_client` as it is a global patch and would impact all consumers
rather than just the ones that rely on synchronous kernel behavior.
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Nice comment - thank you.

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@blink1073 blink1073 left a comment

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Looks good, thank you @dleen!

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dleen commented Nov 15, 2021

@minrk Are you able to take a look?

@minrk minrk merged commit 160c27d into jupyter:master Nov 16, 2021
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minrk commented Nov 16, 2021

Thanks!

yuvipanda added a commit to 2i2c-org/utexas-image that referenced this pull request Apr 8, 2022
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4 participants