link-out

Overview

The link-out node acts as a virtual wire sender. It sends messages to one or more link-in nodes without a physical wire on the canvas. It supports two modes: standard link mode sends messages one-way, while return mode enables subroutine-style calls where the response comes back to the calling flow.

Properties

Operating Modes

// Flow A:
// [Process] -> [Link Out] -----> (to Link In)
//
// Flow B:
// [Link In] -> [Log] -> [Store]
// Messages flow one direction only

// Flow A (caller):
// [Process] -> [Link Out: return]
//           <- [receives result back]
//
// Flow B (subroutine):
// [Link In] -> [Transform] -> [Link Out: return]
// Result is sent back to Flow A

Example: Send to Shared Logging Pipeline

Route log messages from any flow to a centralized logging pipeline using link mode.

// Link Out node in each flow (link mode)
{
  "mode": "link",
  "linkIds": ["central-logger-link-in"],
  "scope": "global",
  "name": "Send to Logger"
}

// Usage pattern in any flow:
// [Any Node] -> [Change: add log metadata] -> [Link Out: Logger]

// The Change node adds metadata before sending:
{
  "rules": [
    { "type": "set", "property": "payload.logLevel", "value": "info" },
    { "type": "set", "property": "payload.source", "value": "api-gateway" },
    { "type": "set", "property": "payload.timestamp", "value": "$now()" }
  ]
}

// Multiple Link Out nodes across different flows
// all point to the same central logger Link In

Example: Subroutine Call with Return Mode

Call a shared validation pipeline and receive the result back in the calling flow.

// Caller flow: Link Out in return mode
{
  "mode": "return",
  "linkIds": ["validator-link-in"],
  "scope": "global",
  "name": "Call Validator"
}

// Caller flow layout:
// [HTTP In] -> [Link Out: return] -> [HTTP Response]
//                                     ^^ receives validated result

// Validation subroutine flow:
// [Link In: "Validator"] -> [Function: validate] -> [Link Out: return]

// The validation function:
var data = msg.payload;
var errors = [];

if (!data.email || !data.email.includes("@")) {
  errors.push("Invalid email");
}
if (!data.name || data.name.length < 2) {
  errors.push("Name too short");
}

msg.payload = {
  valid: errors.length === 0,
  errors: errors,
  data: data
};

return msg; // Returned to calling flow

Common Use Cases