Device Twin Delta

This topic is used to subscribe to device twin delta events. When a device twin changes, the twin properties whose actual values are different from expected values are returned.

Topic

$hw/events/device/{device_id}/twin/update/delta

Parameter	Type	Description
device_id	String	End device ID.

Usage

Use an MQTT client to subscribe to this topic.

Parameter Description

Parameter	Type	Description
event_id	String	Event ID.
timestamp	Int64	Timestamp when the event occurred.
twin	Object	A set of updated device twins. Each twin is in the key-value pair format. The value contains the option flag, the twin metadata contains the value type, the expected status contains the expected value and update time, and the actual status contains the actual value and update time.
delta	Map	Names of twin properties whose actual values are different from expected values, and expected values of these properties.

Example

When an end device is bound to an edge node, the following message is received:

$hw/events/device/{device_id}/twin/update/delta

{
     "event_id":"b9625811-f34f-4252-bee9-98185e7e1ec7",
     "timestamp":1557314742131,
     "twin":{
         "state":{
             "expected":{
                 "value":"running",
                 "metadata":{
                     "timestamp":1557314742122
                 }
             },
             "optional":true,
             "metadata":{
                 "type":"string"
             }
         }
     },
     "delta":{
         "state":"running"
     }
 }