Fixes the "dead node shown NOMINAL" silent outage: node status was set only by
events and never expired, so a node that crashed/lost connectivity stayed
"online" forever (chelsty-infra was online for 16d, piha ~6d). The only thing
that flipped status to offline was a node_offline event, which an unreachable
node can never emit.
Now node status is derived from freshness (now - last_seen), recomputed every
observer cycle (incl. cycles with no new events):
- always-on: fresh <=180s, stale 180-600s, dead >600s (3x the 60s heartbeat)
- remote/LTE (chelsty-*): fresh <=900s, stale 900-3600s, dead >3600s
Thresholds + tier logic live in ONE shared helper, services/control-plane/src/
liveness.py, imported by the observer and both operator UIs (bind-mounted into
the agent-system webui image). No 3x copy.
Transitions are not silent: the observer emits node_stale / node_offline /
node_online (recovery) events tagged source=observer (skipped on re-ingest so
they never reset last_seen), routed by the supervisor to alert_only actions.
Read-time safety net: both UIs recompute liveness from last_seen at request
time, so a stalled observer still surfaces dead nodes. Services inherit their
node's liveness (cascade, variant B) without mutating services.json.
Replaces the earlier binary NODE_OFFLINE_TTL_SECS flip.
Tests: liveness unit tests, observer 3-state + transitions/recovery/baseline +
self-event skip, operator_ui read-time net + cascade, supervisor node-event
routing. 89 passed. docker compose config valid for both stacks.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
