The post-graceful-drain is-active poll used a fixed 10s timeout, but
systemd's hermes-gateway.service has RestartSec=30 — so systemd won't
respawn the unit for 30s after exit-75, and our poll gives up during
the cooldown. Result: every 'hermes update' printed
⚠ hermes-gateway drained but didn't relaunch — forcing restart
followed by a redundant 'systemctl restart' that kicked the newly-
respawning gateway again (and re-started WhatsApp / Discord a second
time in the process).
Fix: read RestartUSec from the unit via 'systemctl show' and set the
poll budget to max(10s, RestartSec + 10s slack). Units without
RestartSec set (or value=infinity) fall back to the original 10s.
Observed timeline from journalctl before fix:
08:56:22.262 old PID exits 75
08:56:32.707 systemd logs Stopped -> Started (10.4s gap, > 10s budget)
After fix the poll covers 40s — comfortably inside RestartSec + slack.
Validation:
- RestartUSec parser tested against '30s', '100ms', '1min 30s',
'infinity', '', 'garbage', '500us', '2min' — all correct.
- Against the live hermes-gateway.service: parses to 30.0s.
- tests/hermes_cli/test_update_gateway_restart.py: 41/41 pass.
5006b2204b