Decode InvokeCommandOutput.Payload object on "@aws-sdk/client-lambda" Javascript v3 package

Question

Describe the issue

I am invoking my lambda function like so in express.JS TypeScript,

import type {InvokeCommandOutput} from '@aws-sdk/client-lambda';
import {InvokeCommand} from '@aws-sdk/client-lambda';

const command = new InvokeCommand({
  FunctionName: this.client_name,
  InvocationType: 'RequestResponse',
  Payload: Buffer.from(JSON.stringify(event)),
});
const response: InvokeCommandOutput = await this.client.send(command);
const payLoad = response.Payload;

if (payLoad != undefined) {
  return response.Payload;
}

Expecting the following response on the InvokeCommandOutput.Payload object from my lambda function.

{
  "challenge_name": "CHALLENGE_NAME",
  "session":  "session string"
}

. I did this using the following package https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-lambda/index.html

I've also tried the example on AWS as well as the toUtf8 and fromUtf8 functions in the SDK to decode the UINT8Array. However, they give me the following error.

{"errorType":"TypeError","errorMessage":"The \"key\" argument must be of type string or an instance of ArrayBuffer, Buffer, TypedArray, DataView, KeyObject, or CryptoKey. Received null","trace":["TypeError [ERR_INVALID_ARG_TYPE]: The \"key\" argument must be of type string or an instance of ArrayBuffer, Buffer, TypedArray, DataView, KeyObject, or CryptoKey. Received null","    at new NodeError (node:internal/errors:372:5)","    at prepareSecretKey (node:internal/crypthe \"key\" argument must be of type string or ano/keys:580:11)","    at new Hmac (node:internal/crypto/hash:132:9)","    at createHmac (node:crypto:162:10)","    at AuthService.initiateAuth (/var/task/main.js:57511:48)","    at processTicksAndRejections (node:internal/process/task_queues:crypto/hash:132:9)","    at createHmac (node:cry96:5)","    at async Runtime.handler (/var/task/main.js:34:9)"]}

Links

https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-lambda/classes/invokecommand.html

Update

When when I replace....

if(payLoad != undefined){
                console.info(payLoad);
                return payLoad;
            }

...with

if(payLoad != undefined){
                console.info(payLoad);
                return JSON.parse(Buffer.from(payLoad).toString());
            }

I get the following payload.

Uint8Array(777) [
  123,  34, 101, 114, 114, 111, 114,  84, 121, 112, 101,  34,
   58,  34,  84, 121, 112, 101,  69, 114, 114, 111, 114,  34,
   44,  34, 101, 114, 114, 111, 114,  77, 101, 115, 115,  97,
  103, 101,  34,  58,  34,  84, 104, 101,  32,  92,  34, 107,
  101, 121,  92,  34,  32,  97, 114, 103, 117, 109, 101, 110,
  116,  32, 109, 117, 115, 116,  32,  98, 101,  32, 111, 102,
   32, 116, 121, 112, 101,  32, 115, 116, 114, 105, 110, 103,
   32, 111, 114,  32,  97, 110,  32, 105, 110, 115, 116,  97,
  110,  99, 101,  32,
  ... 677 more items
]

...that gives me the following error. Meaning there's an error in the Payload that could not be decoded.

'The "key" argument must be of type string or an instance of ArrayBuffer, Buffer, TypedArray, DataView, KeyObject, or CryptoKey. Received null'

Vlad Holubiev · Accepted Answer · 2022-10-06 09:12:31Z

6

response.Payload returns Uint8Array. You need first to convert it to a Buffer, then stringify, and then parse JSON.

Replace this line in your code:

return response.Payload;

With this line:

return JSON.parse(Buffer.from(response.Payload).toString())

answered Oct 6, 2022 at 9:12

Vlad Holubiev

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6 Comments

James Nganga Over a year ago

Hey, thanks for the quick response I am getting the following error,

The "key" argument must be of type string or an instance of ArrayBuffer, Buffer, TypedArray, DataView, KeyObject, or CryptoKey. Received null

Vlad Holubiev Over a year ago

@JamesNganga this means your lambda returns null. check for error in your lambda you call. I tested my code with the working lambda and it worked, so the problem must be in the lambda you call

James Nganga Over a year ago

didn't find an error. However I am guessing the following UInt8Array being I recieved could have an issue, is that correct?

James Nganga Over a year ago

Uint8Array(777) [ 123, 34, 101, 114, 114, 111, 114, 84, 121, 112, 101, 34, 58, 34, 84, 121, 112, 101, 69, 114, 114, 111, 114, 34, 44, 34, 101, 114, 114, 111, 114, 77, 101, 115, 115, 97, 103, 101, 34, 58, 34, 84, 104, 101, 32, 92, 34, 107, 101, 121, 92, 34, 32, 97, 114, 103, 117, 109, 101, 110, 116, 32, 109, 117, 115, 116, 32, 98, 101, 32, 111, 102, 32, 116, 121, 112, 101, 32, 115, 116, 114, 105, 110, 103, 32, 111, 114, 32, 97, 110, 32, 105, 110, 115, 116, 97, 110, 99, 101, 32, ... 677 more items ]

Vlad Holubiev Over a year ago

@JamesNganga could it be that the error you see after decoding is coming from the Lambda you invoke?

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