lxc_guests: Enhanced and fixed lxc_guests plugin

[brknkfr]

• Working with systemd and cgroup version 2 (tested on debian bullseye and debian booksworm)
• Fixed processes (with cgroup version 2)
• Simplified labels
• Simplified memory usage graph
• Added CPU usage in percent (using systemd-cgtop)
• Added Tasks
• No cgrouppath guessing
• Removed support for old lxc versions and systems running on cgroup version 1

[kenyon]

Why not update the existing lxc_guests plugin?

[brknkfr]

Why not update the existing lxc_guests plugin?

It would be possible (as everything in informatics), but I think there will be too much so called "workarounds" included to make this plugin compatible to lxc_guests. To name a few "changes" or "problems":

• the old cgroup version 1 has nanoseconds in cpuacct.stat in whereas cgroup version 2 has miliseconds in cpu.stat for usage_usec
• with systemd-cgtop it's easier to get cpu usage in percet whereis older versions of systemd-cgtop can't do that yet
• counting the actual processes is more difficult to do in cgroup2 than in cgroup1 (relates to all the cgrouppath stuff)

so, that's why.

[kenyon]

Yeah, figured lxc_guests2 is not compatible, but if lxc_guests doesn't work on modern systems, is it even worth keeping?

[brknkfr]

In my opinion, lxc_guests could be replaced by lxc_guests2, but there are probably still old systems out there which use the old lxc_guests. In case of a replacement, I don't know if it would be sufficient to just add a note, that old systems should use an older version of lxc_guests or would it be better to give a new name to the lxc_guests2 plugin, something like lxc_containers. What do you think?

[kenyon]

I would just replace lxc_guests with your update. Users should be pinning to specific commits, so I don't think it should break old systems.