Magento load balancer health check script

lbcheck.php

<?php
include './app/Mage.php';

try {
    Mage::app();
    // echo gethostname();
    echo $_SERVER["SERVER_ADDR"]; // local IP, for instances behind ELB
} Catch (Exception $e) {
    header("HTTP/1.0 503 Service Unavailable");
}