systemd[1]: mariadb.service: A process of this unit has been killed by the OOM killer.

For some odd reason ISPConfig is unable to automatically restart DB service after it's been killed by LXC host.
Any tips how to make this work?

 

I think it is not ISPConfig that does service restarts. Have you installed monit and munin?

 

Nope.
I use Proxmox and it comes with all the graphs I need (except DB). ISPconfig has settings for restarting WWW, DB and EMAIL services and these rescue options are enabled by default.
System | Server Config | Rescue
Normally these work but for some reason these do not work when service is killed by OOM.