ApsaraMQ for MQTT:User properties

Use cases

• Device status reporting: Attach device type and location to status messages so downstream consumers can filter or route data without parsing the payload.

• Message routing: Include routing hints such as priority level or target region, enabling distributed systems to direct messages to the correct processing pipeline.

• Audit and traceability: Embed session IDs, user identifiers, or correlation tokens to support security audits and end-to-end message tracing.

How it works

1. A publisher attaches one or more user properties to a PUBLISH packet and sends it to a topic.

2. ApsaraMQ for MQTT stores the user properties alongside the message and forwards them to all matching subscribers.

3. Subscribers receive the full set of user properties with each delivered message, enabling context-aware processing without parsing the payload.

Quick start (Node.js)

The following example publishes a message with user properties and logs the received properties on the subscriber side using the mqtt.js library.

const mqtt = require('mqtt')

const client = mqtt.connect(process.env.MQTT_ENDPOINT, {
  clientId: process.env.MQTT_CLIENT_ID,
  username: process.env.MQTT_ACCESS_KEY,
  password: process.env.MQTT_SECRET_KEY,
  protocolVersion: 5  // MQTT 5.0 required for user properties
})

client.on('connect', () => {
  // Subscribe to the topic
  client.subscribe('sensors/temperature', { qos: 1 })

  // Publish a message with user properties
  client.publish('sensors/temperature', '22.4', {
    qos: 1,
    properties: {
      userProperties: {
        location: 'warehouse-section-a',
        timestamp: '2021-09-15T12:00:00Z'
      }
    }
  })
})

// Log incoming messages and their user properties
client.on('message', (topic, payload, packet) => {
  console.log('Topic:', topic)
  console.log('Payload:', payload.toString())
  console.log('User Properties:', packet.properties.userProperties)
})

Set the following environment variables before running the example:

Limits

Serialization format example:

[{"key":"mQ","value":"test001"},{"key":"MQ","value":"test002"}]