Use extraFiles feature to cull idle kernels

[GeorgianaElena]

Todo:

• Fix culling behavior
• Docs (In pilot repo, for users) when culling happens (Document kernel culling docs#91)
• Docs (In pilot-hubs repo, for us) where it is configured, and how to raise it

Fixes #518

[yuvipanda]

This is great! Can you add a little docs too?

items moved above

[damianavila]

This one looks OK to me.
Wondering how this change will impact our users... I mean, do we need to ANN this somehow to be sure we are not breaking established workflows?

[choldgraf]

Good question - I guess the question is "what is the default behavior" for jupyterhub when this isn't configured? Because I assume that this what our behavior was, since this config wasn't taking effect right?

Maybe related to that - @GeorgianaElena could you add a short section in our docs maybe here: https://pilot.2i2c.org/en/latest/admin/howto/control-user-server.html that explains what this behavior is expected to be for users?

[GeorgianaElena]

Good question - I guess the question is "what is the default behavior" for jupyterhub when this isn't configured? Because I assume that this what our behavior was, since this config wasn't taking effect right?

I think that before this, the kernels were just not being stopped, but rather the entire notebook servers after that default 1h.
But if this is true, I'm wondering whether we should have the kernel culling timeout be shorter than the one of notebook servers.

Right now, they are both 1h and I'm wondering what happens in this scenario, since the kernel stopping is seen by the notebook culler as "activity". Does this mean that the notebook server timeout is reset once a kernel is culled? Does this makes the notebook cull timeout be actually 1h + 1h? @yuvipanda, what do you think?

[damianavila]

Right now, they are both 1h

Btw, I only see a server cull in the CB demo Hub: https://github.com/2i2c-org/pilot-hubs/blob/master/config/hubs/cloudbank.cluster.yaml#L245

Am I missing something or we do not have server culling in most of our Hubs?

[yuvipanda]

@damianavila z2jh enables it by default https://github.com/jupyterhub/zero-to-jupyterhub-k8s/blob/8c4bed8c94fd14fc9292b9f9730a200404a5e6e8/jupyterhub/values.yaml#L554

[yuvipanda]

Thanks @GeorgianaElena

[choldgraf]

This LGTM - I made one comment in the pilot/ docs but 👍 after that!

[damianavila]

@damianavila z2jh enables it by default

And I was obviously missing something... I forgot to check the z2jh stuff before talking, thanks for the reminder!

[yuvipanda]

Not sure if that was clear - but you can now merge this whenever you feel like, @GeorgianaElena

[GeorgianaElena]

Thanks everybody! 🌞

[choldgraf]

Woohoo! 🚀