Root causes:
1. No dedup for monitor restarts — _last_known_state is cleared on stop,
so every restart re-sent notifications for all unhealthy instances.
2. Aggressive error classification — any Docker state other than 'running'
was treated as 'error', including transient 'created' and 'restarting'.
3. Confusing metadata — when new_status == previous_status (after restart),
notifications showed previous_status equal to current status.
Fixes:
- _check_instance: when previous is None (first check) and new_status equals
the DB status, just record the snapshot and skip _handle_state_change.
This prevents duplicate events/notifications on monitor restart.
- _derive_status: only treat 'exited' and 'dead' as error. Preserve current
status for transient Docker states ('created', 'restarting').
- _derive_status: if DB says 'running' but container is 'not_found',
return 'error' instead of preserving 'running' (fixes silent failure).
- _handle_state_change: improved unhealthy message to 'Container tunnel is
unreachable' instead of generic 'Container is now unhealthy'.
Quality gates: py_compile all backend files pass, tsc --noEmit pass,
npm run build pass, 82/82 tests pass
Developer
82091e31a8