If you "kill -9" a process (or oom kills something whatever) is it expected that an application gracefully deal with that?

The reason I ask is if you 'sudo -u postgres postmaster $STUFF' and then 'kill -9' the parent you get a couple of leftover processes. However, if you use systemctl, you don't get the leftover process.

The problem lies when you use etcd (or consul or Zookeeper). These leftover processes are a problem.

Obviously, don't go kill -9ing stuff, and don't run out of RAM, but you build a resilient system for the worst of times, not the best of times.