If the render loop gets stuck inside a plugin's display(), ledmatrix.service
stays active and the panel stays frozen. This adds a way to detect that.
- src/display_watchdog.py (standard library only) sends sd_notify over
$NOTIFY_SOCKET and writes /run/ledmatrix/display-heartbeat.json. Only the
render thread counts: beats from other threads are ignored.
- ledmatrix.service: WatchdogSec=120, NotifyAccess=main,
RuntimeDirectory=ledmatrix (0755), RestartSteps=4 and
RestartMaxDelaySec=2min. It stays Type=simple. run.py widens the watchdog
to 15 min for start-up, and load_plugin() does the same on the render
thread. The loop arms after its first frame.
- /api/v3/health adds checks.display_loop: running, stalled (no heartbeat
for over 60s, which makes the status degraded) or not_reported. With web
login on, a caller who is not logged in still gets only healthy/degraded,
and a stall degrades that answer.
- The update verifier requires a fresh heartbeat from the restarted display
when the display it replaced was writing one. A frozen panel is rolled
back.
- Existing installs get the systemd watchdog only after install_service.sh
is re-run. The heartbeat works right away.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
