Files
parking_solution/wiki/concepts/printer-status-monitoring.md
julian 3e6773a6d5 fix(devices): Cashino printer — ping-only driver (no false status) + Albanian role wording
The Cashino 80mm printer reported wrong status: it ran on the `rongta`
driver, whose readStatus() scrapes the Rongta board's /prn_stat.htm status
page — which the Cashino does not serve — yielding a bogus degraded/page-
error verdict while the printer was online and printing fine. Root cause:
the Cashino is an ESC/POS PRINT clone with no trustworthy STATUS mechanism.

Fix: extract the shared ESC/POS rendering + transport (renderTicket/
renderReport/renderSubscriptionCard/sendRaw/probe + CP852 map + code128/
qrCode) from printer-rongta into drivers/printer-escpos.ts, and add a
dedicated `cashino` driver that reuses that print path but is deliberately
NOT MonitorableDevice (no readStatus). isMonitorable() is then false, so the
device monitor falls back to healthCheck() — a plain TCP reachability ping:
reachable -> ready, unreachable -> offline, never a guessed paper/cover
state it cannot sense. Rongta driver unchanged (still scrapes its page,
still monitorable). Register + re-export cashinoDriver.

Verified at runtime (cashino registered, isMonitorable=false, no readStatus,
healthCheck->offline on unreachable) and live: /api/devices/status shows both
printers ready (lane via ping, booth via page). The live entry-dispenser at
10.0.10.9 was switched rongta->cashino in the operator DB (backed up).

Also fix the Albanian device-role chip wording, which read wrong as a
"{category} {role}" label: access mixed "i përzier" -> "hyrje/dalje"
(it means a barrier spanning both directions); printer lane "korsia" ->
"në korsi"; booth "kabina" -> "në kabinë". English tidied to match
(mixed->entry/exit, lane->at lane, booth->at booth).

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V
2026-06-18 20:00:42 +02:00

5.1 KiB

type, tags, sources, updated
type tags sources updated
concept
parking
printer
device
monitoring
reliability
2026-06-14

Printer status monitoring

Generalised 2026-06-18: the booth's all-device status footer is a separate, unified monitor across every category (relays/readers/cameras/printers) — see device-status-monitoring. This page remains the authority for the printer-specific rich status (paper/cover/cutter) + its SSE stream; both monitors run.

The booth must know a printer is in trouble before a driver presses the entry button and no ticket comes out. So the system polls each printer's live status (paper out, cover open, cutter jam, off-line) and pushes changes to the operator UI. A reliability control, like printer-roles-failover — not a threat-model one.

Where the status comes from (the safe-decode decision)

The raw print socket (TCP 9100) is write-only for us — it returns no paper/cover feedback. ESC/POS printers expose status via real-time queries (DLE EOT n). On the rongta-printer clone we probed, DLE EOT replies do NOT follow the canonical ESC/POS bit layout (the spec's fixed validation bits were wrong, verified on hardware 2026-06-14). Decoding those bits ourselves risked a false-healthy — reporting "paper OK" when it's empty — which is the dangerous direction for an entry lane.

Instead we scrape the device's own status web page (http://<host>/prn_stat.htm). The board decodes the bits itself into labelled Yes/No rows (Cover Is Open, Cutter Error, Paper End, Paper Near End, Printer Off-Line). We trust the device's decode over hand-decoding an undocumented clone.

This is captured as a device capability: MonitorableDevice.readStatus(): PrinterStatus in packages/devices. The Rongta driver implements it; the monitor is device-agnostic via isMonitorable(). A future printer with a different status mechanism just implements the same interface.

A clone WITHOUT a trustworthy status mechanism must NOT implement readStatus. The Cashino 80mm printer prints via the identical ESC/POS stream (shared in drivers/printer-escpos.ts) but serves no /prn_stat.htm page. Running it on the Rongta driver made the monitor scrape a page that isn't there → a bogus degraded/page-error verdict even while the printer was fine (the incident that prompted this). Fix: a dedicated cashino driver that is not MonitorableDevice (no readStatus), so isMonitorable() is false and the monitor falls back to the generic healthCheck() — a plain TCP reachability ping of the print socket: reachable → ready, unreachable → offline, and never a guessed paper/cover state it cannot sense. This is the correct floor for any ESC/POS printer that can't report consumables: report only what you can actually observe. The shared ESC/POS rendering/transport (renderTicket/renderReport/ renderSubscriptionCard/sendRaw/probe) was extracted to printer-escpos.ts so both drivers share the print path and only status differs.

Status mapping (fail safe)

readStatus() maps to ready | degraded | offline:

  • status page unreachable / times out → offline (same signal as a dead printer; never throws),
  • page reachable but a recognised field is missing → degraded ("unexpected status page") — we do NOT claim "ready" off a page we didn't fully parse,
  • any fault flag true (paper end, cover open, cutter error, off-line) → degraded + a detail string ("paper out", …),
  • all five clear → ready.

The monitor (server)

PrinterMonitor (apps/server/src/printer-monitor.ts):

  • reloads the monitored set from devices each tick (so a newly-assigned printer is picked up without a restart), keeping only enabled, monitorable printers;
  • polls every PRINTER_POLL_MS (default 5000ms), never overlapping ticks;
  • caches the latest status per device id;
  • emits a printer-status event on the device bus only when status changes (deduped).

API / live UI

  • GET /api/printers/status — cached snapshot of all printers (no device round-trip).
  • GET /api/printers/status/stream — Server-Sent Events: full snapshot on connect, then one event per change. The booth SPA subscribes for real-time paper-out / offline indicators.
  • Any authenticated role may read (operational, not a setup action).

Verified on hardware (2026-06-14)

readStatus() against 10.0.10.6 → ready (all flags false); against an unreachable host → offline with "status page timeout" (no throw); bus emits on change and suppresses unchanged reads. Full repo typechecks.

Open / not yet done

  • Fault-state capture: we've only observed the all-clear page. The exact label text for an active fault (e.g. does "Paper End" flip to "Yes"?) should be confirmed by physically removing paper / opening the cover, to be 100% sure the scrape catches it. The parser is built to match Yes/No and degrade on anything unexpected, so this is a confidence check, not a blocker.
  • Tying a degraded/offline entry-dispenser into printer-roles-failover failover and the (not-yet-built) entry flow's all-printers-down policy (device-input-flow).