I love preemptible VMs, you and your team's work has made some impressive compute projects financially feasible. :- )
You folks should really have a utility on the default images (maybe call it `seppuku` or `dienow`) which sends an "o" to /proc/sysrq-trigger; using that has allowed me to time shutdowns to within a couple seconds at worst (though there is an unfortunate discrepancy between the account logs, which show the accurate node shutdown time, and the instance logs, which only show it a few seconds later).
You folks should really have a utility on the default images (maybe call it `seppuku` or `dienow`) which sends an "o" to /proc/sysrq-trigger; using that has allowed me to time shutdowns to within a couple seconds at worst (though there is an unfortunate discrepancy between the account logs, which show the accurate node shutdown time, and the instance logs, which only show it a few seconds later).