(zmqhandlers.py) RuntimeWarning: coroutine 'WebSocketHandler.get' was never awaited

[convoliution]

Attempting to connect to a kernel results in this error being thrown, in a fresh install of the jupyter pip package.

Based on this StackOverflow post and the fact that Tornado released a new major version two hours ago, I believe this is a compatibility issue with Tornado v6.0

Manually reverting to Tornado v5.1.1 resolved this issue, but Jupyter should be updated or its dependency requirement changed.

[kevin-bates]

Could you please provide Traceback information relative to this issue? The message implies it would be something the caller failed to do. So I think we need to drill down a bit.

This sounds more sinister than the previous incompatibility introduced by a Tornado release.

[convoliution]

Not sure if this is what you mean, but this is the Notebook server's entire output in my terminal:

[I 09:11:05.940 NotebookApp] Serving notebooks from local directory: [REDACTED]
[I 09:11:05.940 NotebookApp] The Jupyter Notebook is running at:
[I 09:11:05.940 NotebookApp] http://localhost:8888/
[I 09:11:05.940 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[I 09:11:49.436 NotebookApp] Kernel started: 6c8f3e7c-fcb1-48e4-be95-91baa14f99d3
[I 09:11:50.886 NotebookApp] Adapting to protocol v5.1 for kernel 6c8f3e7c-fcb1-48e4-be95-91baa14f99d3
[REDACTED]/venv/lib/python3.6/site-packages/notebook/base/zmqhandlers.py:284: RuntimeWarning: coroutine 'WebSocketHandler.get' was never awaited
  super(AuthenticatedZMQStreamHandler, self).get(*args, **kwargs)
[W 09:11:51.924 NotebookApp] Replacing stale connection: 6c8f3e7c-fcb1-48e4-be95-91baa14f99d3:ad37ee996ad749368d8745648c8af729
^C[I 09:12:29.162 NotebookApp] interrupted

[zlargon]

I run the command pip install "tornado<6" to fix the issue.

I also meet the same issue. My jupyter notebook could work yesterday but doesn't work this morning.
I use the virtualenv as package manager, and here is the difference between the package dependencies:

• jsonschema: 3.0.0 -> 3.0.1
• tornado: 5.1.1 -> 6.0

packages	work fine	not work
appnope	0.1.0	0.1.0
attrs	18.2.0	18.2.0
backcall	0.1.0	0.1.0
bleach	3.1.0	3.1.0
certifi	2018.11.29	2018.11.29
chardet	3.0.4	3.0.4
decorator	4.3.2	4.3.2
defusedxml	0.5.0	0.5.0
entrypoints	0.3	0.3
facebook-sdk	3.1.0	3.1.0
idna	2.8	2.8
ipykernel	5.1.0	5.1.0
ipython	7.3.0	7.3.0
ipython-genutils	0.2.0	0.2.0
ipywidgets	7.4.2	7.4.2
jedi	0.13.3	0.13.3
Jinja2	2.10	2.10
* jsonschema	* 3.0.0	* 3.0.1
jupyter	1.0.0	1.0.0
jupyter-client	5.2.4	5.2.4
jupyter-console	6.0.0	6.0.0
jupyter-core	4.4.0	4.4.0
MarkupSafe	1.1.1	1.1.1
mistune	0.8.4	0.8.4
nbconvert	5.4.1	5.4.1
nbformat	4.4.0	4.4.0
notebook	5.7.4	5.7.4
pandocfilters	1.4.2	1.4.2
parso	0.3.4	0.3.4
pexpect	4.6.0	4.6.0
pickleshare	0.7.5	0.7.5
pip	19.0.3	19.0.3
prometheus-client	0.6.0	0.6.0
prompt-toolkit	2.0.9	2.0.9
ptyprocess	0.6.0	0.6.0
Pygments	2.3.1	2.3.1
pyrsistent	0.14.11	0.14.11
python-dateutil	2.8.0	2.8.0
pyzmq	18.0.0	18.0.0
qtconsole	4.4.3	4.4.3
requests	2.21.0	2.21.0
Send2Trash	1.5.0	1.5.0
setuptools	40.8.0	40.8.0
six	1.12.0	1.12.0
terminado	0.8.1	0.8.1
testpath	0.4.2	0.4.2
* tornado	* 5.1.1	* 6.0
traitlets	4.3.2	4.3.2
urllib3	1.24.1	1.24.1
wcwidth	0.1.7	0.1.7
webencodings	0.5.1	0.5.1
wheel	0.33.1	0.33.1
widgetsnbextension	3.4.2	3.4.2

[mars-f]

I got my notebook to connect by downgrading tornado from 6.0.0 to 5.1.1:

$ pipenv install "tornado<6"
$ pipenv run pip freeze |grep tornado
tornado==5.1.1

[kevin-bates]

RuntimeWarning: coroutine 'WebSocketHandler.get' was never awaited
 super(AuthenticatedZMQStreamHandler, self).get(*args, **kwargs)

@convoliution - yes this is helpful. I believe the call to the superclass needs an await. I can take a peek at this.

However, I suspect this is one of those tip of the iceberg things - and we might be better off capping tornado < 6.0 if it turns into a slippery slope. Sorry, I can't refuse a cliche when it's there. 😄

[kevin-bates]

I should have looked at the code prior to my response. Turns out @takluyver added a yield via #4392. In addition, Thomas capped tornado < 6 in early January.

That said, when I run the master tip with tornado 6, I still see issues - different from above.

Since it doesn't appear these changes are in any releases, I suspect it would be good to build a release that caps tornado.

cc: @minrk

[chansen2000]

a good way！valid

I run the command pip install 'tornado<6' to fix the issue.

[zxh126]

I run the command pip install tornado==5.1.1 to fix the issue.
but who kowns why?

[minrk]

Merging with #4439

[drishyamlabs]

This command worked for me:

pip install 'tornado<6'

[verata-veritatis]

Unfortunately, I use packages that require the most up-to-date tornado. Jupyter should consider updating.