Add support for cross-building for ARM

[holdenk]

I run a mixed arm & amd64 cluster so I've been using a forked version of the Dockerfiles. I figured I'd clean them up a bit and see if y'all are interested.

[jacobtomlinson]

Hey @holdenk. Great to see you here!

Thanks so much for raising this. This would close #128.

Looks like CI is failing. If I remember right from the last time we tried this it's because buildkit doesn't support loading contexts with subdirectories like we do here with :base-notebook.

dask-docker/docker-compose.yml

Line 25 in 5c77838

context: github.com/jupyter/docker-stacks.git#master:base-notebook

Do you have any thoughts on how we can work around this?

[holdenk]

.@jacobtomlinson I'm not super familiar with that part, normally I'd just copy the directory to make it accesiable in the build context or set up a symlink. I can take a look but it might take me a few cycles to figure out :)

[jacobtomlinson]

Thanks for pushing some changes here @holdenk.

I'm a little worried that this change means our base image will be Python 3.8 and the notebook image will be Python 3.9. We try hard to keep these environments in lock step.

See specific comments below.

[jacobtomlinson]

This is looking awesome thanks @holdenk!

This seems ready, are you good for me to merge?

[holdenk]

Yeah let's go ahead and merge this I've got one follow on PR that I'll raise for making this compatible with the JupyterHub launcher :)

[holdenk]

Actually I think I've discovered a problem with the mamba part, give me a minute.

[holdenk]

Ah yup found it, only showed up on ARM but I had a bad thing in my bash command let me just validate it.

[holdenk]

Fixed it :) Launches locally on ARM as well now & loads dask.

[jacobtomlinson]

Woo thanks @holdenk!