The thermal printer drained overnight (2026-05-18/19) because the old
notify.py POSTed one print job per Grafana webhook fire. With 9
concurrently-firing alerts (zabbix-postgres + fc-devicemgmt + brochure
+ PrintPaperRollLow), every evaluation cycle stamped fresh CUPS jobs
onto the queue until the operator physically powered the printer off.
This refactor:
- Adds env-var config: THERMAL_PRINT_ENABLED (master kill switch),
BATCH_INTERVAL_MIN (default 60), BATCH_MAX_PENDING (default 50).
- IRC delivery stays per-event (operator wants the live stream).
- Thermal routing now:
* critical/disaster/page severity OR alert_channel=thermal_print_immediate
-> print immediately
* alert_channel=thermal_print -> enqueue into hourly digest
* RESOLVED -> remove from digest buffer (no resolution-spam prints)
* else -> IRC only, no thermal
- Background digest_loop thread flushes the buffer hourly (or sooner
if buffer hits BATCH_MAX_PENDING). Digest payload is a single
Print.Web /api/print/alert POST listing distinct alertnames + per-rule
target counts.
- New POST /flush endpoint (manual operator force-flush; useful for
testing without waiting an hour).
- GET / returns config + buffer depth + per-stat counters for observability.
Net effect: max 1 thermal print per BATCH_INTERVAL_MIN for batched
warnings, plus immediate prints for criticals. Closes the 2026-05-18/19
alert-storm incident.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bacac067cf