prometheus-nats-exporter has never served a metric. Upstream's module
renders `-addr … -port … ${extraFlags} ${url}` and defaults extraFlags
to the empty list, but the binary refuses to start without at least one
collector: it exits 1 with "no Collectors specified". So the unit logged
Started, the process was gone milliseconds later, and every scrape was
refused -- up=0 continuously, scrape_duration 0.6ms, zero samples.
Verified by running the exact argv both ways: without a collector it
exits 1, with -varz it stays up and logs the listener. A bogus flag is
rejected with exit 2, so the check measures acceptance rather than
tolerance.
varz is the server itself, connz makes a client that will not stay
connected visible, and jsz covers JetStream, which this swarm uses for
the status KV. The rest describe a clustered deployment we do not have.
An empty list is not a neutral default when the program requires a flag,
and nothing about it is visible to evaluation -- which is why the gate
now reads the rendered ExecStart rather than only asserting enable.
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