Josh Josh - 3 months ago 16
Node.js Question

Node.JS Lambda Function Not Returning JSON

I'm new to NodeJS, and JS in general (mostly a PHP and C# guy), so I could really use some help with this function below.

The goal is to receive a JSON payload, connect to MySQL, and then return the results of the query in a JSON response. I've got it connecting to the DB, I can read the JSON data that it receives (event.fieldname) but for some reason it's not sending back the JSON for the applicant_data variable.

Do I just have the variable in the wrong location? When I run the code below I just get back "{}" as the returned data.

Thanks in advance for the help!

NodeJS Code:

exports.handler = function(event, context, callback) {
console.log('Starting:');
console.log("Request received:\n", JSON.stringify(event));

var mysql = require('mysql');



var jsonconnection = mysql.createConnection({
host: 'servername',
user: 'username',
password: 'password',
database: 'database'
});

jsonconnection.connect();
console.log('Connected to MySQL:');

jsonconnection.query('SELECT applicant_id FROM customers WHERE applicant_id = \'' + event.applicant_id + '\'',
function(err,res){
if(err) throw err;

console.log('Row Details:', JSON.stringify(res));
var applicant_data = {
applicant_id : res.applicant_id
};

jsonconnection.end();

context.succeed(applicant_data);
})
};

Answer

I am not familiar with AWS, but base on http://docs.aws.amazon.com/lambda/latest/dg/nodejs-prog-model-handler.html, following code may work.

exports.handler = function (event, context, callback) {
    console.log('Starting:');
    console.log("Request received:\n", JSON.stringify(event));

    var mysql = require('mysql');

    var jsonconnection = mysql.createConnection({
        host: 'servername',
        user: 'username',
        password: 'password',
        database: 'database'
    });

    // Move applicant_data outside of query as it will be needed at the end in callback
    var applicant_data = {};

    jsonconnection.connect();
    console.log('Connected to MySQL:');

    jsonconnection.query('SELECT applicant_id FROM customers WHERE applicant_id = \'' + event.applicant_id + '\'',
        function (err, res) {
            if (err) throw err;

            console.log('Row Details:', JSON.stringify(res));
            applicant_data = {
                // Only use first row of data
                applicant_id: res[0].applicant_id;
            };

        });

    // Move connection end out side of query
    jsonconnection.end();

    // This should return your data, in JSON form
    callback(null, JSON.stringify(applicant_data));

    // I assume this is the correct use for succeed
    context.succeed();
};