svos-dev challenged a claim this README made -- that a crash-loop yields one
message per episode -- with a measurement: one 2026-09-19 boot-gate refusal on
svos.service produced FIVE transitions into failed, and the operator got five
messages.
Measured here before accepting it, because a peer's number is still a number
someone else took: a unit with Restart=on-failure, burst 3, interval 30s
produced 7 journal failure lines and exactly ONE notifier invocation. So the
multiplier is not universal -- it needs retries spanning start-limit windows or
an external restarter. svos.service carries StartLimitIntervalSec=5min, which
is how it accumulated five.
Both conditions exist on this box, so the guard goes in as cheap insurance
rather than as a fix for something proven here. The README now states both
numbers and which restart policy each of the twelve units carries, since that
is what decides the exposure. Noted with it: hermes-gateway has start limiting
DISABLED, so it retries forever and may never reach failed at all -- worth
knowing before trusting this alarm to cover it.
Design, taken from svos-dev's shape:
- Keyed on a hash of the CAUSE (unit + result + exit status + the shape of
its last error lines), never the unit name alone. A genuinely different
failure inside the window is a new fact and must still page; suppressing by
unit would hide a second, worse failure behind the first.
- Suppression is LOGGED to suppressed.log, never silent. An alarm that
quietly declines to fire is indistinguishable from one that is broken.
⚠ The first test of this appeared to show the cooldown not working, and the
test was wrong rather than the code -- it invoked the script BEFORE failing the
unit, so the two calls legitimately saw different states and computed different
fingerprints. Re-run the way systemd actually invokes it: same cause 3x -> 1
sent, 2 suppressed and logged; a different cause inside the same window -> sent.
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