---
paths:
  - "nodes/*/src/nodeClass.js"
---

# Telemetry Rules

## Output Port Convention
- Port 0: Process data (downstream node consumption)
- Port 1: InfluxDB telemetry payload
- Port 2: Registration/control plumbing

## InfluxDB Payload Structure
Port 1 payloads must follow InfluxDB line protocol conventions:
- **Tags**: Low-cardinality indexed fields (node name, machine type, station ID)
- **Fields**: High-cardinality values (measurements, setpoints, quality scores)

## Cardinality Rules
- **Never add high-cardinality tags** — no timestamps, UUIDs, or free-text values as tags
- Tags are for grouping/filtering; fields are for values
- New tags require review for index impact

## FlowFuse Dashboard Compatibility
- Charts use `msg.topic` for series identification (`category: "topic"`)
- Dashboard API endpoints serve pre-aggregated data
- Changes to Port 0 `msg.topic` format can break downstream dashboards

## Consistency
- Field names for the same measurement type must be consistent across all nodes
- Measurement names follow a documented naming convention
- Aggregation windows (1min, 5min, 1hr, 24hr) are standardized