Busy indicator shows wrong status

[davidbrochart]

Description

When running a single cell, the busy indicator sometimes shows a half-filled circle.

busy.mp4

Reproduce

1. mamba install jupyterlab
2. pip freeze shows jupyterlab 3.5.2 and ipykernel 6.19.4
3. Execute a simple time.sleep(1)
4. Randomly see the wrong busy indicator.

Expected behavior

The busy indicator should show a filled circle when only one cell is executing.

Context

• Operating System and version: Linux Ubuntu 21.04
• Browser and version: Google Chrome Version 108.0.5359.124
• JupyterLab version: 3.5.2

[trungleduc]

Thanks @davidbrochart for reporting it. The indicator makes an assumption that if two cells are executed consequently and the delay between them is under 1000ms, they are counted as a group of two execution so that you will see a half-filled circle.

jupyterlab/packages/notebook/src/executionindicator.tsx

Lines 454 to 456 in 60ddcbf

	state.timeout = window.setTimeout(() => {
	state.needReset = true;
	}, 1000);

I don't know if 1000ms is too big, we might lower it down to 500ms.

[davidbrochart]

This seems very arbitrary and error prone. Shouldn't the kernel status on IOPub be used instead?

[trungleduc]

I count one second after the kernel idle message of the IOPub channel. If we don't have this delay when you manually execute multiple simple cells, the execution status is reset after each cell and we can't count the total cells scheduled.

[davidbrochart]

Ah I see, then 1 second is too much IMO, it should be something like 100 ms.