Pre-loading notebooks?

[ericmjl]

First off, wanted to ping in and say that I was able to display a bokeh plot embedded in a panel tab served up by voila. Voila! 😄

I have one question regarding load times, when myself and my colleague @zbarry did some debugging. Some notebooks are inherently slow to run, e.g. the imports take some time. For user experience, might it be possible to pre-load a notebook kernel right after launching voila? While I'm not sure how exactly the implementation would look, might it look like a flag that enables "always keeping one extra jupyter kernel running" that a new user could connect to, rather than having a kernel created upon HTTP request?

[timkpaine]

How would you do user authentication? Let's say your notebook fetches data, how would you ensure that when a given user gets to the web page, that they had the requisite permissions to run that code to access the data in the first place

[ericmjl]

Hmmm, I'm not quite sure how the authentication story would work, I have to admit. Most of how I've used voila in the past doesn't involve passwords and the likes, and the way I've used it with my colleagues before been 'here's the URL - have fun with it!'

[maartenbreddels]

@timkpaine good point about authentication.

@ericmjl
There are some thoughts about this.

• Pre-start kernels (saves startup time of a kernel, starting Python, setting up zmq socket etc, and various imports)
• Pre-import modules, e.g. importing numpy,scipy,mpl (but not adding them to the namespace, just make sure they are in sys.modules)
• Fork kernels. Execute a notebook once, then for every request fork that final state. A POC can be found here: WIP: Feature: fork kernel ipython/ipykernel#410 . This can be seen as a cache of processes, where the cache key is notebook path, and possibly other values, such as credentials, as Tim mentioned.

I think all of this should not be turned on by default, but I'd like to see this configurable somehow. Especially in the simple case of 1 voila, 1 notebook, no login, the forking would work great.

[maartenbreddels]

See #30, better to continue there.