link-in

Overview

The link-in node acts as a virtual wire receiver. It receives messages sent by link-out nodes without requiring a physical wire connection on the canvas. This enables clean flow organization by connecting distant parts of a flow or linking across entirely separate flows. Link In nodes can receive from multiple Link Out nodes simultaneously.

Properties

Scope Modes

scope: "flow"
// Only Link Out nodes on the
// same flow tab can send here

scope: "global"
// Any Link Out node in any flow
// can send messages to this node

Example: Reusable Error Handler

Create a centralized error handler that receives errors from multiple flows via virtual wires.

// Link In node: "Error Handler" (global scope)
{
  "linkId": "error-handler-link",
  "scope": "global",
  "name": "Error Handler Receiver"
}

// This Link In receives errors from multiple flows:
// - Flow 1: API Gateway  -> Link Out -> [Error Handler]
// - Flow 2: MQTT Handler -> Link Out -> [Error Handler]
// - Flow 3: File Watcher -> Link Out -> [Error Handler]

// Downstream processing after Link In:
// 1. Switch node routes by error severity
// 2. Critical errors -> Email notification
// 3. All errors -> Database log
// 4. Warning errors -> Dashboard update

// Message format received:
{
  "payload": {
    "error": "Connection timeout",
    "severity": "critical",
    "source": "mqtt-broker-1",
    "timestamp": "2025-01-15T10:30:00Z"
  }
}

Example: Shared Data Processing Pipeline

Build a reusable data normalization pipeline that multiple input flows feed into.

// Link In node: "Data Normalizer" (global scope)
{
  "linkId": "data-normalizer-input",
  "scope": "global",
  "name": "Normalize Pipeline Entry"
}

// Multiple data sources feed into this pipeline:
// - REST API endpoint sends raw JSON
// - CSV file reader sends parsed rows
// - MQTT subscriber sends sensor payloads

// The pipeline after this Link In:
// [Link In] -> [Validate Schema] -> [Transform] -> [Enrich]
//           -> [Store in DB] -> [Link Out: "processed"]

// Each source uses a Link Out node pointed at this Link In,
// so the normalization logic is defined only once.
// Any changes to the pipeline apply to all data sources.

Common Use Cases