Livebook hangs when handling large source smart cells

[fahchen]

Hey guys, thank you for the amazing work you’re doing here. I really appreciate it!

I recently created a kino smart cell that allows to draw excalidraw graphs in the Livebook. You can check it out at https://github.com/fahchen/kino_excalidraw. However, I’ve run into an issue where the Livebook sometimes hangs. After some investigation, I found that Livebook.Text.Delta.diff/2 takes a significant amount of time to compute, especially as increasing as the source of the smart cell grows larger. Actually, I embed the excalidraw file which is in JSON format, into the notebook. Here’s the relevant part of the code:

livebook/lib/livebook/session.ex

Line 1792 in d3161c6

delta = Livebook.Text.Delta.diff(cell.source, source)

I’d like to ask for your help with following:

1. is this a proper way to embed the excalidraw into the livebook notebook?
2. wow can I address this issue? My current solution is to add an option to generate Kino.nothing() as the source.

livebook-diff-issue.md (GitHub doesn’t allow uploading .livemd files, so I changed it to .md.)
Here’s an example livebook note that embeds an excalidraw graph, alternatively you can find an example from the kino_excaildraw document(https://hexdocs.pm/kino_excalidraw/components.html).

To reproduce this issue, you can open the example notebook from the above, draw a complex graph, and then Livebook will hang.

Thanks in advance for any help or suggestions.

[jonatanklosko]

@fahchen what code is the smart cell supposed to generate? Looking at the source I see the generate code does KinoExcalidraw.SmartCell.new, but then you implement Kino.Render for that struct that renders nothing. Is it for use later?