Allow restarting xpra to reconnect to abandoned xorg session.
There are some issues that cause xpra to crash, e.g. #2730
What I see then on xpra server host is this:
[ ~]$ xpra list Found the following xpra sessions: /run/user/3035/xpra: UNKNOWN session at :123 Re-probing unknown sessions in: /run/user/3035/xpra UNKNOWN session at :123 (cleaned up)
I can still see that Xorg is up as well as apps I have been running:
2230560 /usr/libexec/Xorg -noreset -novtswitch -nolisten tcp +extension GLX +extension RANDR +extension RENDER -auth /home/mj/.Xauthority -logfile /run/user/3035/xpra/Xorg.:123.log -configdir /run/user/3035/xpra/xorg.conf.d/2230559 -config /etc/xpra/xorg.conf -depth 24 :123
So if only xpra server could be restarted, find the existing Xorg session and reconnect to it, then it would mitigate problems with xpra stability.
xpra start :123 --use-display=yes
In v4, this is automatic, even over ssh: ticket:2523#comment:8.
xpra upgrade :123 from time to time resets the xpra server but not the X windows so it is possible to reattach with reduced memory usage
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2746