When is a kernel considered idle

[katsar0v]

There is a setting MappingKernelManager.cull_idle_timeout which says:

kernel is considered idle and ready to be culled

If cull_busy and cull_connected are both set to False, when is a kernel connected idle? Following use cases are not clear to me:

• Notebook App is opened in browser and all cells of the notebook are run. Is the kernel afterwards considered idle if the browser window is opened for like 24 hours and there is no activity?
• Notebook App has one cell which has a while True loop. Browser window is closed. Is the kernel considered idle? (My guess is no, but maybe it should be considered)
• Last use cases: I opened a notebook with lots of data, which was loaded into various variables. I have finished my work and I closed the window. Is the kernel considered idle, if there is no client/browser activity?

Thanks for the help in advance, I guess it is mainly a documentation issue and just understanding the MappingKernelManager configs.

[takluyver]

The way it works at present is that the kernel sends a 'busy' message when it starts executing a request, and an 'idle' message when it finishes. So it's idle if there's not code running. The 'while True' loop would leave it busy.

Code execution isn't the only kind of request, though. Among other things, when you open a notebook in a tab, it will make a kernel info request, which will reset the timer.

[katsar0v]

Thank you for the clarification @takluyver