Cannot exit ipython with running qcodes.Monitor()

[michaelc12qe]

Steps to reproduce

iPython version 8.10, qcodes version 0.42, Windows 10 Pro 22H2

1. open ipython
2. from qcodes import Monitor
   monitor = Monitor()
3. exit ipython

It hangs instead of closing iPython. The terminal must be terminated.

[jenshnielsen]

I can reproduce this. Not sure what is going on but perhaps related to #3814

It would be nice to investigate if changing the monitor thread to be a deamon thread would also resolve this issue

[jenshnielsen]

Note that until this is resolved it can be mitigated by explicitly calling join on the monitor thread

❯ ipython
Python 3.11.5 | packaged by Anaconda, Inc. | (main, Sep 11 2023, 13:26:23) [MSC v.1916 64 bit (AMD64)]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.18.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from qcodes import Monitor
In [2]: m = Monitor()
In [3]: m.join()
In [4]: exit

~ took 29s
❯

[michaelc12qe]

I've tested turning the monitor thread into a daemon thread as you suggested, by passing the keyword argument daemon=True into the Monitor initialization. It appears to resolve this issue. I've also checked that the behaviour of the monitor remains unchanged by add QDAC2 voltage channels to the monitor, and it seems fine.

I don't know if there's any more testing required, but happy to raise a PR for this if you like.

[jenshnielsen]

@michaelc12qe In the long term I would like to come up with something slightly cleaner than deamon mode but I agree that in the short term using deamon is the best solution. So please go ahead