# Telemetry

> **Reflects code as of `9ab9f6b` · regenerated `2026-05-11`**

What every EVOLV node emits on each of its three output ports, the InfluxDB line-protocol layout, and how the data reaches Grafana/FlowFuse.

## Three-port model

```mermaid
flowchart LR
    sc[specificClass<br/>tick or event]:::tier3
    nc[nodeClass<br/>outputUtils.formatMsg]:::tier2
    p0[(Port 0<br/>process)]:::p0
    p1[(Port 1<br/>InfluxDB line)]:::p1
    p2[(Port 2<br/>registration)]:::p2

    sc -->|getOutput| nc
    nc --> p0
    nc --> p1
    nc --> p2

    p0 -. delta-compressed payload .-> dl[Downstream<br/>Node-RED logic]:::neutral
    p1 -. line protocol .-> influx[(InfluxDB)]:::ext
    p2 -. child.register .-> parent[Parent EVOLV node]:::neutral

    classDef tier3 fill:#50a8d9,color:#000
    classDef tier2 fill:#86bbdd,color:#000
    classDef p0 fill:#86bbdd
    classDef p1 fill:#a9daee
    classDef p2 fill:#dddddd
    classDef neutral fill:#dddddd
    classDef ext fill:#fff2cc
```

## Port 0 — Process data (delta-compressed)

**Purpose:** feeds downstream Node-RED logic — dashboards, control functions, alarms.

**Shape:** `msg.payload` is an object containing **only keys that changed** since the last tick. Consumers cache + merge.

**Why delta-compressed:** at 1 Hz ticks with 50 fields per node, full snapshots flood downstream nodes and dashboards. Delta payloads typically carry 0–5 fields per tick.

**Example (rotatingMachine, 1 tick):**

```json
{
  "topic": "rotatingMachine#pump-A",
  "payload": {
    "flow.predicted.downstream.default": 12.4,
    "predictionConfidence": 0.87
  }
}
```

Most other fields (state, pressure, mode, …) didn't change this tick — omitted.

**Trigger:** `outputUtils.checkForChanges()` compares the current `getOutput()` against the previous snapshot.

## Port 1 — Telemetry (InfluxDB line protocol)

**Purpose:** time-series storage in InfluxDB for trending, regulatory reporting, ML training.

**Shape:** `msg.payload` is a **string** (or array of strings) in InfluxDB line protocol:

```
<measurement>,<tag-set> <field-set> <timestamp-ns>
```

**Example:**

```
rotatingMachine,id=pump-A,softwareType=rotatingMachine flow_predicted_downstream=12.4,power_measured_atequipment=18.2 1714752000000000000
```

**Conventions:**

| Element | Rule |
|---|---|
| measurement (table) | The node's `softwareType` (lowercase). |
| tag-set | Low-cardinality identity: `id`, `softwareType`, location-style tags. **Never** raw measurement values. |
| field-set | Numeric values only. Keys flatten `<type>_<variant>_<position>` (underscore, not dot — InfluxDB constraint). |
| timestamp | Nanoseconds. Set by `outputUtils` from the node's clock. |

See [InfluxDB schema design](concepts/influxdb-schema-design) for the cardinality discipline.

## Port 2 — Registration / control

**Purpose:** upward `child.register` at startup; later, internal control msgs (the registry-driven command replies).

**Shape:**

```json
{
  "topic": "child.register",
  "payload": {
    "ref": <node reference>,
    "softwareType": "machine",
    "config": { ... }
  }
}
```

**Trigger:** the nodeClass adapter emits `child.register` on `init` if a `parent` is configured. The parent's `commandRegistry` dispatches into `ChildRouter.onRegister(...)`.

## The output composition pipeline

```mermaid
sequenceDiagram
    participant tick as Tick (1 Hz)
    participant sc as specificClass
    participant mc as MeasurementContainer
    participant ou as outputUtils
    participant ports as Ports 0 / 1

    tick->>sc: tick()
    sc->>sc: concern modules update mc + state
    sc->>ou: getOutput() snapshot
    ou->>ou: diff vs last
    alt no change
        ou-->>sc: skip
    else change
        ou->>ports: Port 0 — JSON delta
        ou->>ports: Port 1 — line protocol
    end
```

`outputUtils` is the single place the platform serialises state. Never write directly to `node.send` from specificClass — go through `outputUtils.formatMsg`.

## InfluxDB layout

Recommended schema for EVOLV's data:

| InfluxDB element | Maps to |
|---|---|
| Database / bucket | One per plant (or per environment: `evolv_dev`, `evolv_prod`). |
| Measurement (table) | Node softwareType (`rotatingMachine`, `pumpingStation`, …). |
| Tags | `id` (instance id), `softwareType`, `area`, `processCell`, `unit` (for hierarchical drill-down). |
| Fields | Numeric series — every key from `getOutput()` that has a numeric value, flattened with `_`. |
| Retention | Hot bucket: 7 days @ 1 s. Cold bucket: 1 year @ 1 min downsample. |

**Cardinality discipline:** keep tag sets stable. Don't put `state` (string) as a tag — emit it as a field with code (`state_code=2`). High-cardinality tags fragment the index.

## FlowFuse dashboard wiring

If you use FlowFuse `ui-chart` widgets, Port 0 is the natural source — the delta-compressed JSON maps cleanly to `msg.topic` (series label) + `msg.payload` (y-value).

Layout rule for charts (from `.claude/rules/node-red-flow-layout.md` §4):
- One chart per metric type (one for flow, one for power, one for level).
- A trend-feeder function splits Port-0 deltas into per-series outputs, each output wired to one chart.
- The chart's `category: "topic"` + `categoryType: "msg"` plots one series per unique `msg.topic`.

```mermaid
flowchart LR
    p0[(Port 0)]:::p0
    split[trend-feeder<br/>function (N outputs)]:::tier2
    chart1[ui-chart: flow]:::neutral
    chart2[ui-chart: power]:::neutral

    p0 --> split
    split --> chart1
    split --> chart2

    classDef p0 fill:#86bbdd
    classDef tier2 fill:#86bbdd,color:#000
    classDef neutral fill:#dddddd
```

## Grafana dashboard provisioning

`dashboardAPI` consumes registrations and emits Grafana dashboard JSON via HTTP. Wiring:

```mermaid
flowchart LR
    evolv[EVOLV node<br/>any softwareType]:::tier3
    dash[dashboardAPI]:::util
    grafana[(Grafana HTTP API<br/>POST /api/dashboards/db)]:::ext

    evolv -->|child.register| dash
    dash -->|composed JSON| grafana

    classDef tier3 fill:#50a8d9,color:#000
    classDef util fill:#dddddd
    classDef ext fill:#fff2cc
```

dashboardAPI looks up a template per softwareType (in `nodes/dashboardAPI/src/config/templates/`), substitutes the node's id + tags, and POSTs an upsert. Bearer-token auth is supported.

## Common debug recipes

| Symptom | First check |
|---|---|
| InfluxDB rows missing for a node | Confirm Port 1 is wired to an `influxdb out` node. Tap Port 1 with a debug node to verify line-protocol output. |
| Dashboard widgets stuck on `n/a` | Confirm Port 0 is reaching the trend-feeder. Many widgets need `msg.topic` set for series labelling. |
| `child.register` not arriving at parent | Tap Port 2 with debug. Confirm parent's `commandRegistry` accepts `child.register` (or the legacy `registerChild` alias). |
| Too many InfluxDB writes (high write-rate) | Check that `outputUtils.checkForChanges()` is firing. Likely you wired a tick-driven debug node bypassing the delta filter. |
| Grafana dashboard not created on plant boot | Inspect dashboardAPI's HTTP response. Check the bearer token + base URL in its config. |

## Related pages

- [Architecture](Architecture) — output port wiring in the 3-tier code
- [Topic-Conventions](Topic-Conventions) — what topics map to what fields
- [InfluxDB schema design](concepts/influxdb-schema-design) — cardinality discipline