Related to answer for: http://stackoverflow.com/questions/22238744/node-mysql-reusable-connection-module/22318071

db_connect.js

console.log('db_connect module initialized');
var mysql      = require('mysql');

function createConnection(){
    var connection = mysql.createConnection({
        host     : 'localhost',
        user     : 'xyz',
        password : 'xyz',
        database : 'xyz',
        debug    : false
    });
    return connection;
}

exports.createConnection = createConnection;
exports.mysql = mysql;

jt-test.js

var v = require('./validator');
var timers = require('timers');
var connections = 0;

timers.setInterval(function(){
    v.validate('bagehot','foo',function(err,result){
        if (err)
            console.log('failed', err);
        else
            console.log('success! ',result);
    });
},2000);

try-this.js

console.log('server module initialized');
var express = require('express');
var login = require("./login");
var validator = require("./validator");
var app     = express();

function loginFail(req,res,mext){
    res.end('failed');

};
function loginSucceed(req,res,next){
    res.end('OK');
}
function listen() {
    app.use(express.bodyParser());

    app.get('/login', function(req, res) {

        var username = req.query.username;
        var password = req.query.password;

        console.log('User ' + username + ' is attempting login...');

        validator.validate(username,password,function(err,result){
            if (err) loginFail(req,res,err);
            else loginSucceed(req,res,result);
        });
    });

    app.listen(8080, function() {
        console.log('Server running at http://127.0.0.1:8080/');
    });
}

listen();

validator.js

console.log('validator module initialized');
var connect = require("./db_connect");

exports.validate = validate;

function validate(username, password, callback){

    var connection = connect.createConnection();
    //the idea is for this to return the object, connection,
    //which opens a new connection

    connection.connect(function (err){
        if (err) return callback(new Error('Failed to connect'), null);
        console.log('Connection with the Officeball MySQL database openned...');

        connection.query("select 'bagehot' as username,'foo' as password,'walter' as fname, 'bagehot' as lname,12 as rank, 'yes' as active from dual",
            username,
            function(err,rows,fields) {
                connection.destroy();
                console.log('...Connection with the Officeball MySQL database closed.');
                if (err)
                    return callback(new Error ('Error while performing query'), null);
                if (rows.length !== 1)
                    return callback(new Error ('- [Anomaly] - Failed to find exactly one user'), null);

                if (rows[0].password === password & rows[0].active === "yes") {

                    var result = new Object;

                    result.username = rows[0].username;
                    result.password = rows[0].password;
                    result.fname = rows[0].fname;
                    result.lname = rows[0].lname;
                    result.rank = rows[0].rank;

                    return callback(null, result);

                } if(rows[0].active !== "yes"){

                    return callback(new Error ('User account not active.'), null);

                }else {

                    return callback(new Error ('Login credentials did not match.'), null);

                }

            });


    });
};