AWS Unrecognizable Lambda Output Cognito error

Question

I recently started working with AWS. I have integrated AWS Amplify using cognito user pools for my user management(login&signup) and it went perfect(User pool gets updated whenever a new user registers). Now i have added an Cognito Post confirmation trigger to save the registered email into database and here is my trigger codevar mysql = require('mysql');

var config = require('./config.json');

var pool = mysql.createPool({

host : config.dbhost,

user : config.dbuser,

password : config.dbpassword,

database : config.dbname

});

exports.handler = (event, context, callback) => {

let inserts = [event.request.userAttributes.email];

context.callbackWaitsForEmptyEventLoop = false; //prevents duplicate entry

pool.getConnection(function(error, connection) {

connection.query({

sql: 'INSERT INTO users (Email) VALUES (?);',

timeout: 40000, // 40s

values: inserts

}, function (error, results, fields) {

// And done with the connection.

connection.release();

// Handle error after the release.

if (error) callback(error);

else callback(null, results);

});

});

};

whenever a user registers and confirms his email this trigger invokes and throws me this error "Unrecognizable Lambda Output Cognito ". Even though it throws me this error in the background my DB is getting inserted with new registered email, but i am unable to redirect my page due to this. Any help will be appreciated. Thanks

Aravind

Answer 1

Short answer: Replace callback(null, results); to callback(null, event);

Reason: You have to return the result that Cognito will use it for continue the authentication workflow. In this case, this is event object.