JupyterLab session wedged when Voilà pane opened

[fperez]

Description

I'm sorry that this is a rather vague report. Leaving it here mostly as a placeholder in case it either rings a bell, or if we can reproduce it again later so we can update here. But please feel free to close this for now if there's no actionable ideas...

As shown in this issue for the Berkeley student hubs and shown on this image:

we had a student who after clicking (accidentally, as we don't use Voilà in that course) on the Voilà Lab icon, ended up with a strangely wedged server, with all home directory files disappearing from the listing and no action possible. Our solution was to manually delete the workspace files (by ssh-ing in through the Google Cloud Console) and things came back to normal.

Reproduce

Unfortunately I don't know - when I tried following similar steps I didn't see the problem, and because this is a production hub for a very large class, we've for now simply removed Voilà as we can't take the risk and don't need it for this course. If we happen to find a way to reproduce, we'll update here.

cc @yuvipanda - reported here as per your notes in our 2688.

Context

• voila version: 0.2.10.
• Operating System and version: cloud-hosted JupyterHub on GCP.
• Browser and version: not sure.

If using JupyterLab

• JupyterLab version: 3.1.10

Installed Labextensions

Note that this won't show the voila extension, which has now been removed but was active at the time:

JupyterLab v3.1.10
/opt/conda/share/jupyter/labextensions
        jupyterlab-jupytext v1.3.4 enabled OK (python, jupytext)
        ipycanvas v0.9.0 enabled OK
        jupyterlab-plotly v5.2.1 enabled OK
        jupyter-matplotlib v0.9.0 enabled OK
        @jupyter-server/resource-usage v0.6.0 enabled OK (python, jupyter-resource-usage)
        @retrolab/lab-extension v0.2.2 enabled OK
        @jupyter-widgets/jupyterlab-manager v3.0.1 enabled OK (python, jupyterlab_widgets)
        @jupyterlab/geojson-extension v3.1.2 enabled OK (python, jupyterlab-geojson)
        @jupyterlab/server-proxy v3.1.0 enabled OK

[jtpio]

Thanks @fperez for reporting.

At first glance, it looks like it could be something related to Voila (in that case running as a server extension) blocking the main thread, which would then prevent JupyterLab from replying to the contents requests. Something also mentioned by @yuvipanda in berkeley-dsep-infra/datahub#2688 (comment).

If we manage to get a repro for this issue, we could open the dev tools and check in the network tab whether these requests are being fulfilled.

[fperez]

Thanks @jtpio - will keep that in mind if we happen to see it again, good pointer, at least it gives us something to start from :)

Feel free to close this for now as I doubt we'll have anything actionable in the short term, I don't want to clog your issues log. I'll repost/reopen if we have more info later.