Kernels restart when jupyter is shutting down

[drevicko]

Describe the bug
While shutting down Jupyter notebook (with ctrl-c in the terminal), it shut down the running kernels, but the kernels restarted a few milliseconds later. The newly started kernels then realised they don't have a parent and shut themselves down.

Here's the log from the shutdown and jupyter versions (it was installed by conda I believe):

^C[I 06:16:45.905 NotebookApp] interrupted
Serving notebooks from local directory: /home/ian/github/out-of-scope-intent
2 active kernels
Jupyter Notebook 6.2.0 is running at:
http://localhost:8888/?token=950e3a5c79b86ea3bb62e330ad605452fd3a7cbe4ece42c0
 or http://127.0.0.1:8888/?token=950e3a5c79b86ea3bb62e330ad605452fd3a7cbe4ece42c0
Shutdown this notebook server (y/[n])? y
[C 06:16:48.592 NotebookApp] Shutdown confirmed
[I 06:16:48.593 NotebookApp] Shutting down 2 kernels
[I 06:16:48.895 NotebookApp] Kernel shutdown: 1d6d85b4-1c13-4a84-960e-635d721ecdb7
[I 06:16:49.196 NotebookApp] Kernel shutdown: 05ba3ac5-999f-47b6-9c53-802b94d85914
[I 06:16:49.197 NotebookApp] Shutting down 0 terminals
[I 06:16:49.198 NotebookApp] KernelRestarter: restarting kernel (1/5), keep random ports
[I 06:16:49.202 NotebookApp] KernelRestarter: restarting kernel (1/5), keep random ports
$ [IPKernelApp] WARNING | Parent appears to have exited, shutting down.
[IPKernelApp] WARNING | Parent appears to have exited, shutting down.

$ jupyter --version
jupyter core     : 4.7.1
jupyter-notebook : 6.2.0
qtconsole        : 5.0.2
ipython          : 7.20.0
ipykernel        : 5.3.4
jupyter client   : 6.1.7
jupyter lab      : 2.2.6
nbconvert        : 6.0.7
ipywidgets       : 7.6.3
nbformat         : 5.1.2
traitlets        : 5.0.5

To Reproduce
I had some difficulty reproducing this and it's the first time I've seen it, so here's some context (which may or may not be red herrings!):

• I had just closed a chrome window that had a tab with one of the kernels
• The connection is tunnelled ssh (may have introduced some latency??)
• The connection had been down overnight and had just been reconnected (not sure at all why that'd make a difference...)

Expected behavior
The kernels don't restart when jupyter is shutting down.

Desktop (please complete the following information):

• MacOS Mojave 10.14.6 (18G7016)
• Chrome (though it happened in the terminal)
• Version 88.0.4324.182 (Official Build) (x86_64)