User disruptions in Jupyter Lab during hub restarts, I think

[consideRatio]

I've noticed disruptions during hub upgrades for users within Jupyter Lab, but why this happens I'm uncertain of, and I've even forgotten the error messages seen for the user at the moment.

I suspect though, that traffic routing may have changed, perhaps that relates to some adjustment we made in kubespawner to make hub restarts better recover from issues of for example a evicted pod? Hmmm...

I consider this issue description a work in progress, as I'm still putting together essential pieces to understand the issue in itself.

Relevant log entries from the hub pod on startup

[reflector:199] watching for pods with label selector='component=singleuser-server' in namespace jupyterhub
[reflector:199] watching for events with field selector='involvedObject.kind=Pod' in namespace jupyterhub

[app:1888]      user1@example.com still running
[app:1888]      user2@example.com still running
[app:1888]      user3@example.com still running
[app:2337]      Hub API listening on http://0.0.0.0:8081/hub/
[app:2339]      Private Hub API connect url http://10.68.35.211:8081/hub/
[app:2352]      Not starting proxy

[proxy:319]     Checking routes
[proxy:399]     Adding default route for Hub: / => http://10.68.35.211:8081
[proxy:344]     Adding missing route for /user/user2@example.com/ (Server(url=http://10.72.7.108:8888/user/user2@example.com/, bind_url=http://10.72.7.108:8888/user/user2@example.com/))
[proxy:344]     Adding missing route for /user/user1@example.com/ (Server(url=http://10.72.7.105:8888/user/user1@example.com/, bind_url=http://10.72.7.105:8888/user/user1@example.com/))
[proxy:344]     Adding missing route for /user/user3@example.com/ (Server(url=http://10.72.7.111:8888/user/user3@example.com/, bind_url=http://10.72.7.111:8888/user/user3@example.com/))
[proxy:261]     Adding user user2@example.com to proxy /user/user2@example.com/ => http://10.72.7.108:8888
[proxy:261]     Adding user user1@example.com to proxy /user/user1@example.com/ => http://10.72.7.105:8888
[proxy:261]     Adding user user3@example.com to proxy /user/user3@example.com/ => http://10.72.7.111:8888

[app:2422]      JupyterHub is now running at http://10.68.37.189:80/

[consideRatio]

Closed by #1401 and #1404.