jupyterhub-lab support will be enabled if $JUPYTER_ENABLE_LAB is set.

[clkao]

Closes #531.

[parente]

@clkao thanks for looking into this. Is that environment variable set by JupyterHub automatically? If so, great. If not, we prefer documenting how users may change the start command instead of introducing a custom env var that we have to support long term.

[clkao]

@parente Yes I should add this to the Notebook Options section in README. It seem I should be adding to all of them? Just want to make sure sure that they are not rendered by templates somewhere else.

[parente]

@clkao If there's documentation in JupyterHub or the jupyterhub-lab extension that describes the environment variables and when it's set, we should point to that in the READMEs. That involves updating all of the READMEs at the moment since #538 is still a work in progress.

[clkao]

@parente I've cleaned up this a bit to use JUPYTER_ENABLE_LAB, which is more general for enabling lab via env for both standalone notebook and hub. Let me know if the base-notebook README changes are fine and I'll copy to other READMEs.

[parente]

Later in the READMEs we document the following way to start JupyterLab instead of Notebook in these images with:

docker run -it --rm -p 8888:8888 jupyter/base-notebook start.sh jupyter lab

I'm thinking we should extend the start-singleuser script to accept an alternative command like start.sh does like so:

# defaults to the original behavior of running jupyterhub-singleuser
docker run -it --rm -p 8888:8888 jupyter/base-notebook start-singleuser.sh 
# overrides the command to run jupyter labhub instead
docker run -it --rm -p 8888:8888 jupyter/base-notebook start-singleuser.sh jupyter labhub

That way we can avoid introducing a env var that we have to maintain as a special feature of the stack images. What do you think?

[clkao]

That works too. I still think env var is somewhat less intrusive though. Image you have a jupyterhub with multiple images that some have lab installed, and some might be older ones. Setting the env var now suggests using jupyterlab whenever it is available.

If we require the spawner to specify singleuser_cmd, people using formspawner/profilesspawner will need to carefully select the appropriate start command for individual image.

[parente]

Thanks for the clarification about the use case. I think the env var makes sense, now that I understand some images might have the env var set while others may not.

[parente]

@clkao LGTM. I think the addition to the base-notebook README is fine for now in hopes that we'll have a consolidated ReadTheDocs site soon.