AWS Lambda function doesn't trigger from Cognito PostConfirmation event, but it works in Test

Question

I've created an application that allows users to signup, which adds them into my AWS Cognito user pool. This was done using the AWS-SDK for PHP, specifically the signUp method. I've tried to create a Lambda function that triggers upon PostConfirmation that adds user details into my DynamoDB table and it works when I use the Test feature but when I set it up for live deployment, it won't add users into the table and does not give me any errors.

Here is my method's parameters:

$this->client->signUp([
                'ClientId' => $this->client_id,
                'Username' => $username,
                'Password' => $password,
                'UserAttributes' => [
                    [
                        'Name' => 'name',
                        'Value' => $name
                    ],
                    [
                        'Name' => 'email',
                        'Value' => $email
                    ],
                ]
            ]);

This is my Lambda function:

var aws = require('aws-sdk');
const ddb = new aws.DynamoDB({apiVersion: '2012-10-08'});

aws.config.update({region: 'us-east-1'});

exports.handler = function(event, context, callback) {
    var params = {
            TableName: 'RecipeUsersDB',
            Item: {
                'username': {S: event.request.userName},
                'name': {S: event.request.userAttributes.name},
                'email': {S: event.request.userAttributes.email}
                }
        }
    ddb.putItem(params, function(err, data) {
      if (err) {
        console.log("Error", err);
      } else {
        console.log("Exit", data);
      }
    });
    callback(null);
};

This is the Test event parameters that work:

{
  "request": {
    "userName": "hrefrlo",
    "userAttributes": {
      "sub": "e1feer",
      "name": "2srhserrh",
      "email": "3srwergthgsrg"
    }
  },
  "response": {}
}

I've given the function several different permission policies:

AmazonDynamoDBFullAccess

AmazonCognitoDeveloperAuthenticatedIdentities

AmazonCognitoPowerUser

AWSLambdaBasicExecutionRole

AWSLambdaInvocation-DynamoDB

This is just for a uni assignment so the app(website) is just going to be used for a demo, and is only going to be deployed on Beanstalk. Any help is appreciated, thank you!

this is obvious but not clearly mentioned in the question... did you already confirm the user signup? — reda la
Yes sorry, I should have mentioned that. I have a method that confirms the user using a confirmation code sent to their email. — benjaminl13

benjaminl13 benjaminl13 · Accepted Answer · 2020-05-28T05:48:29

I have realized my silly mistake. Cognito's PostConfirmation response is actually in the form of:

{
    "version": "1",
    "region": "eu-central-1",
    "userPoolId": "eu-central-1_45YtlkflA",
    "userName": "user4",
    "callerContext": {
        "awsSdkVersion": "aws-sdk-java-console",
        "clientId": "4736lckau64in48dku3rta0eqa"
    },
    "triggerSource": "PostConfirmation_ConfirmSignUp",
    "request": {
        "userAttributes": {
            "sub": "a2c21839-f9fc-49e3-be9a-16f5823d6705",
            "cognito:user_status": "CONFIRMED",
            "email_verified": "true",
            "email": "[email protected]"
        }
    },
    "response": {}
}

In my code, I had event.request.userName, when it should have been event.userName.

AWS Lambda function doesn't trigger from Cognito PostConfirmation event, but it works in Test

1 Answers