How to publish mqtt to AWS Shadow from Lambda

Question

This is the code I'm currently using

var AWS = require('aws-sdk');

var iotdata = new AWS.IotData({
  endpoint: '######.iot.ap-south-1.amazonaws.com'
});

exports.handler = async (event) => {


await new Promise((resolve, reject) => {
   var params = {
  payload: Buffer.from('...') || 'STRING_VALUE' , 
  
  thingName: 'ESP32', /* required */
  //shadowName: 'STRING_VALUE'
 };
  iotdata.updateThingShadow(params, function(err, data) {
      if (err) { 
         console.log(err, err.stack); 
         console.log("error................")// an error occurred
         reject(err);
      } else {
         console.log(data);           // successful response
         resolve(data)
      }
 });
})
}

I have two questions regarding this,

There seems to be some mistake in my code. Can you please help me to correct this.
In which format should I give the payload. I dont really understand the buffer type.

Somehow when I run the code error........... is seen in the execution result.(This is from the console log)

I am running this code inside a AWS lambda in a Node js 12.x environemnt. I have given proper permission for lambda to publish data into the shadow.

Thank you..

This is the error message,

Response:
{
  "errorType": "InvalidRequestException",
  "errorMessage": "Payload contains invalid json",
  "trace": [
    "InvalidRequestException: Payload contains invalid json",
    "    at Object.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/json.js:51:27)",
    "    at Request.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/rest_json.js:55:8)",
    "    at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:106:20)",
    "    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:78:10)",
    "    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:688:14)",
    "    at Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:22:10)",
    "    at AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)",
    "    at /var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10",
    "    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:38:9)",
    "    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:690:12)"
  ]
}

Request ID:
"2574b62-4b-41e7-a725-644e8d78"

Function logs:
START RequestId: 24574b62-4be3-41e7-a725-694a444e8d78 Version: $LATEST
2020-11-14T04:39:40.303Z    24574b62-4be3-41e7-a725-694a444e8d78    INFO    InvalidRequestException: Payload contains invalid json
    at Object.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/json.js:51:27)
    at Request.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/rest_json.js:55:8)
    at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:688:14)
    at Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:22:10)
    at AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)
    at /var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10
    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:38:9)
    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:690:12) {
  code: 'InvalidRequestException',
  time: 2020-11-14T04:39:40.243Z,
  requestId: '219f8c5f-2bf1-9ad0-ff5d-589940833983',
  statusCode: 400,
  retryable: false,
  retryDelay: 68.01088760246567
} InvalidRequestException: Payload contains invalid json
    at Object.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/json.js:51:27)
    at Request.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/rest_json.js:55:8)
    at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:688:14)
    at Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:22:10)
    at AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)
    at /var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10
    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:38:9)
    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:690:12)
2020-11-14T04:39:40.340Z    24574b62-4be3-41e7-a725-694a444e8d78    INFO    error................
2020-11-14T04:39:40.342Z    24574b62-4be3-41e7-a725-694a444e8d78    ERROR   Invoke Error    {"errorType":"InvalidRequestException","errorMessage":"Payload contains invalid json","code":"InvalidRequestException","message":"Payload contains invalid json","time":"2020-11-14T04:39:40.243Z","requestId":"219f8c5f-2bf1-9ad0-ff5d-589940833983","statusCode":400,"retryable":false,"retryDelay":68.01088760246567,"stack":["InvalidRequestException: Payload contains invalid json","    at Object.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/json.js:51:27)","    at Request.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/rest_json.js:55:8)","    at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:106:20)","    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:78:10)","    at Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:688:14)","    at Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:22:10)","    at AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)","    at /var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10","    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:38:9)","    at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:690:12)"]}
END RequestId: 24574b62-4be3-41e7-a725-694a444e8d78
REPORT RequestId: 24574b62-4be3-41e7-a725-694a444e8d78  Duration: 736.20 ms Billed Duration: 800 ms Memory Size: 128 MB Max Memory Used: 85 MB  Init Duration: 392.36 ms

I think the error message is clear: "Payload contains invalid json". What is the form of your payload? — Marcin
@Marcin I want something like this to be published. How should I do it. I dont udnerstand how to format the payload — Senuda Jayalath
{ "state": { "desired": { "color": { "r": 10 }, "engine": "ON" } } } — Senuda Jayalath

Senuda Jayalath Senuda Jayalath · Accepted Answer · 2020-11-14T05:09:12

I have found the answer to the problem.

The problem was in the payload. This would be the correct code...

var AWS = require('aws-sdk');

var iotdata = new AWS.IotData({
  endpoint: '#######.iot.ap-south-1.amazonaws.com'
});

exports.handler = async (event) => {

var POST_DATA = JSON.stringify({"state":{"desired":{"state":10}}});
await new Promise((resolve, reject) => {
   var params = {
  payload:POST_DATA , 
  
  thingName: 'ESP32', /* required */
  //shadowName: 'STRING_VALUE'
 };
  iotdata.updateThingShadow(params, function(err, data) {
      if (err) { 
         console.log(err, err.stack); 
         console.log("error................")// an error occurred
         reject(err);
      } else {
         console.log(data);           // successful response
         resolve(data)
      }
 });
})

}

How to publish mqtt to AWS Shadow from Lambda

1 Answers