svos-dev found an interaction between the two detectors by doing the recovery
rather than reasoning about it: clearing a failed unit is REQUIRED before
systemd will start it again, and reset-failed zeroes NRestarts in the same
motion. Verified here -- a start-limited unit refused to start until
reset-failed, which took NRestarts 3 -> 0.
So the standard recovery from a failed-START alarm erases the history a flap
sampler would depend on, routinely rather than as an edge case. A unit that
fails, is cleared, then flaps starts its history from zero, delaying the first
flap alarm by the whole threshold -- exactly the window where a just-fixed unit
is most likely still sick. Mitigation recorded: store a last-seen timestamp so
a counter going BACKWARDS is itself detectable as a reset rather than read as
quiet.
Also recorded as its own shape: 'nothing to count is not the same as not
counting'. The first manual-restart check read NRestarts flat and would have
concluded a sampler goes blind whenever a human touches a unit. Artifact of the
test -- that unit had already hit its start limit and stopped auto-restarting,
so the instrument was reading correctly from a subject that had stopped
producing. Verify, then ask what the verification could not have seen.
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