OOMScoreAdjust can be set between -1000 and +1000. This value is inherited
and systemd has no easy way to control this for children (box code also
runs as non-root, so it cannot easily set it for the children using
/proc/<pid>/oom_score_adj.
When set to -1000 and the process reaches the MemoryMax, it seems the kernel
does not kill any process in the cgroup and it spins up in high memory. In fact,
'systemctl status <service>' stops displaying child process (but ps does), not sure
what is happenning.
Keeping it -999 means that if a child process consumed a lot of memory, the kernel
will kill something in the group. If the main box itself is killed, systemd will
kill it at all because of KillMode=control-group.
Keeping it -999 also saves box service group being killed relative to other docker
processes (apps and addons).
Fixes#605
this allows backups to take more memory as part of the systemd group.
the node box code itself runs under little more constraints using
--max_old_space_size=150
