Prometheus Metrics & Health Monitoring Reference

Production OT observability, Grafana dashboard integration, and Kubernetes/Docker readiness probes for opcua2mqtt edge fleets.

Exported Prometheus Metrics (/metrics)

• opcua_tags_polled_total — Counter of total OPC UA tag samples acquired from PLCs.
• mqtt_messages_published_total — Counter of MQTT and Sparkplug B payloads acknowledged by the broker.
• wal_buffer_depth_records — Gauge of pending telemetry records queued in the disk Write-Ahead Log.
• opcua_cycle_duration_seconds — Histogram of acquisition loop latency for SLA verification.

Health & Readiness Endpoints

Configure Docker or K3s liveness probes against GET /healthz (returns HTTP 200 OK when the gateway event loop is healthy, or HTTP 503 during degraded startup).