Slow Connection to Jupyter Notebook on WSL2 - jupyter-notebook

Question

I'm having a weird problem with Jupyter notebook running inside a WSL2 instance. Every time I start a new notebook, my first connection to localhost:8888 (or localhost:XXXX for any other port number) takes a LONG time to connect, like 5-10 minutes. Once one connection to that port has been made, however, all subsequent connections happen at a normal speed. As far as I can tell the delay is not specifically happening within the Jupyter server, as the server output doesn't show any GET requests during the waiting period:
> jupyter notebook .
[I 08:29:21.282 NotebookApp] Authentication of /metrics is OFF, since other authentication is disabled.
[W 08:29:21.729 NotebookApp] All authentication is disabled. Anyone who can connect to this server will be able to run code.
[I 08:29:21.732 NotebookApp] Serving notebooks from local directory: /home/peter/jade_poplar/code/python
[I 08:29:21.732 NotebookApp] Jupyter Notebook 6.4.0 is running at:
[I 08:29:21.732 NotebookApp] http://localhost:8888/
[I 08:29:21.732 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
...
5-10 MINUTES ELAPSE
...
[I 08:38:12.718 NotebookApp] 302 GET / (127.0.0.1) 2.110000ms
However, the issue does appear to be limited only to Jupyter: if I just listen on the port with nc -l 8888 and then point my browser to localhost:8888 the GET request shows up immediately.
I have tried random fixes to other problems that I found on SE, eg. this one, but to no avail. Any advice, or even a suggestion as to where to start looking, would be greatly appreciated! This is driving me bonkers, although I am getting a lot of chess in while I wait for my notebooks to load :D

Answer 1

Old answer
I found 2 ways to get around the "waiting time" on my system.
Hit Ctrl+C once after the console output hangs at Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
Set the DISPLAY environment variable to nothing: DISPLAY= jupyter notebook .. Apparently, the same trick works for pip.
UPDATE 1
After some debugging I figured out, that the --no-browser option does the trick as well:
jupyter notebook --no-browser .
jupyter-notebook by default opens localhost:8888 in the browser.
I assume WSL2 has problems opening the default browser, and therefore times out.
UPDATE 2
To confirm my guess, from UPDATE 1, I set up WSL to be able to open a browser window:
Installing firfox in WSL (ubuntu):
sudo apt install firefox
Setting up X11 forwarding on WSL2
Using this setup jupyter-notebook starts normally and localhost:8888 is opened in firefox.