Question

I have created three EC2 instances, two of instances are web servers and one instance is a MySQL server. I would like to connect to the MySQL server and retrieve data. I was wondering how I can send a SQL query to the MySQL server.

<?php

$server = "localhost";
$username = "username";
$password = "password";
$database_name = "dbname";

$dbconnect = mysql_connect($server, $username, $password);

if(!$dbconnect)
{
    //connection failed to the host
    echo "-1";
    exit;
}

if(!mysql_select_db($database_name))
{
    //cannot connect to database
    echo "-2";
    exit;
}

?>

I used this php script to connect to the local mysql server. If I want to connect to the remote MySQL server on EC2 instance then do I just simply replace the server address to the IP address (elastic IP address) of the EC2 instance that running MySQL server?

Answer 1

Instead of using the Elastic IP address, use the DNS name associated with the Elastic IP address. It will resolve to the internal IP address associated with the current instance mapped to the Elastic IP address. This saves you in latency and cost.

Here’s an article I wrote that describes this approach:

Using Elastic IP to Identify Internal Instances on Amazon EC2
http://alestic.com/2009/06/ec2-elastic-ip-internal

You’ll also need to make sure that your MySQL database is listening on 0.0.0.0 instead of 127.0.0.1. Check that your MySQL database server is not accessible from the Internet.