[winswitch] checkpoint xpra docker container

Matthieu Imbert matthieu.imbert at inria.fr
Mon Jun 8 15:13:15 BST 2020


Hi,

I'm trying to checkpoint a docker container running an xpra server, 
which runs an x11 app (i'm currently testing with xcalc).

My goal is to be able to checkpoint (and stop) the container, then 
restart it later, and connect (through xpra) to the x11 app in the same 
state as it was at the time of the checkpoint.

Under the hood, docker uses criu (https://criu.org/Main_Page) to do the 
checkpointing. I understand that doing that directly with the x11 app is 
not possible because there is part of the state which is inside the x11 
server, thus not accessible to criu, this is why I think that embedding 
everything in a docker container with xpra might be the solution, 
because everything is inside the container, so we may reasonably expect 
that all relevant state will be saved with a docker checkpoint.

For now, i'm able to checkpoint the container without error, and restart 
the container from the checkpoint, but when the container is restarted, 
xpra restarts from scratch (at least, this is what it looks like, when 
looking at the container logs) and the x11 app is restarted as well, and 
thus looses its state.

Do you have an idea of what goes wrong here, and is there a way to fix it?

Here are the details of my test: everything is here: 
https://github.com/mimbert/docker-xpra-criu-test with instructions on 
how to reproduce.

An execution log is here: 
https://github.com/mimbert/docker-xpra-criu-test/blob/master/execution.log
line 66 is the moment I do the checkpoint
line 68 is the moment I restart the container

(I also posted to the criu community)

Cheers,

-- 
Matthieu Imbert


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