Trigger Related Entities via Relation

This tutorial demonstrates how to trigger a related device action based on telemetry received from another device using the Rule Engine.

Use case

A Smoke Detector reports telemetry: smoke = "true"

ThingsBoard:

creates a Smoke Alarm
finds a related Fire Alarm System
sends an RPC command to activate it

When smoke != "true":

the alarm is cleared

Architecture

Devices

Smoke Detector with the type Smoke Sensor
Fire Alarm System with the type Fire Alarm Device

Relation

Smoke Detector -- Uses --> Fire Alarm System

Rule chains

modified Root Rule Chain
new Related Fire Alarm System rule chain

Step 1. Create devices

Create two devices:

Device 1

Name: Smoke Detector
Type: Smoke Sensor

Device 2

Name: Fire Alarm System
Type: Fire Alarm Device

Step 2. Create relation

Create a relation:

From: Smoke Detector
To: Fire Alarm System
Relation type: Uses

Step 3. Create rule chain

You can import a ready-made rule chain or build it manually.

Option 1. Import rule chain

Download the Related Fire Alarm System rule chain as a JSON file and import it into your instance.

Option 2. Create manually

Create a new rule chain named Related Fire Alarm System, open it, and add the following nodes:

Step 3.1 Check Relation Presence node

Add the Check Relation Presence node and connect it to the Input node.

This node will check the relation from the Fire Alarm System device to the originator of the message Smoke Detector using the type and direction of relation. If the relation exists, the message will be sent through the True chain.

Fill in the fields:

Name: Check Relation
Relation search parameters:
- Direction: To originator
- Relation type: Uses
- Check relation to specific entity: Fire Alarm System device

Step 3.2 Change Originator node

Add the Change Originator node and connect it to the Check Relation Presence node with a relation type True.

This node will change the originator from the Device Smoke Detector to the related Device Fire Alarm System and the submitted message will be processed as a message from another entity, namely Fire Alarm System.

Fill in the fields:

Name: Change Originator
New originator: Related entity
Relations query:
- Direction: From originator
- From originator: 1
Relation filters:
- Relation type: Uses
- Entity types: Device

Change originator rule node configuration

Step 3.3 Script Transformation node

Add the Transformation Script node and connect it to the Change Originator node with a relation type Success. Enter the Name field as New RPC message.

This node will transform an original message into RPC request message.

The RPC call will have 2 properties:

Property	Value
method	ON
params	{}

In order to do this, add the following Script:

TBEL
JavaScript

newMsg = {};
if (msg.smoke == 'true') {
newMsg.method = 'ON';
}
newMsg.params = {};
return {msg: newMsg, metadata: metadata, msgType: msgType};

var newMsg = {};
if (msg.smoke == 'true') {
newMsg.method = 'ON';
}
newMsg.params = {};
return {msg: newMsg, metadata: metadata, msgType: msgType};

Script node for RPC message transformation

Step 3.4 RPC call request node

Add the RPC call request node and connect it to the Transformation Script node with a relation type Success.

This node takes the message payload and sends it as a response to the Message Originator Fire Alarm System.

Fill in the fields with the input data shown in the following table:

Name: Fire Alarm System
Fire Alarm System: 60

Step 3.5 Check the node connections

Input ⇾ Check Relation
Check Relation ⇾ True ⇾ Change Originator
Change Originator ⇾ Success ⇾ New RPC message
New RPC message ⇾ Success ⇾ Fire Alarm System

This Rule chain is ready. Save it.

Completed rule chain for related fire alarm system

Step 4. Modify the Root Rule Chain

In the Root Rule Chain, add these nodes after Save Timeseries node:

Step 4.1 Filter Script node

Add the Filter Script node and connect it to the Save Timeseries node with a relation type Success.

Enter the Name field as Smoke Alarm Filter.

This node will check if data of incoming message is smoke using the following script:

TBEL
JavaScript

return msg.smoke == 'true';

return msg.smoke == 'true';

Step 4.2 Clear Alarm node

Add the Clear Alarm node and connect it to the Filter Script node with a relation type False.

Enter the Name field as Clear Smoke Alarm and the Alarm type as Smoke Alarm.

This node loads the latest Alarm with configured Alarm Type for Message Originator Smoke Detector and Clears the Alarm if it exists.

Step 4.3 Create Alarm node

Add the Create Alarm node and connect it to the Filter Script node with a relation type True.

Enter the Name field as Create Smoke Alarm and the Alarm type as Smoke Alarm.

This node tries to load the latest Alarm with configured Alarm Type for Message Originator, namely Smoke Detector.

Step 4.4 Rule Chain node

Add the Rule Chain node and connect it to the Filter Script node with a relation type True.

Enter the Name field as Related Fire Alarm System.

This node forwards incoming Message to specified Rule Chain Related Fire Alarm System.

Step 4.5 Check the node connections

Save Timeseries ⇾ Success ⇾ Smoke Alarm Filter
Smoke Alarm Filter ⇾ False ⇾ Clear Smoke Alarm
Smoke Alarm Filter ⇾ True ⇾ Create Smoke Alarm
Smoke Alarm Filter ⇾ True ⇾ Rule Chain Input