app.js

require('pmx').init({
    http: true,
    network: true
});

var http = require('http');
var url = require('url');
var request = require('request');
var config = require('config');
var probe = require('pmx').probe();
var StatsD = require('node-statsd'),
    client = new StatsD();

http.createServer(onRequest).listen(80);

var counter = 0;
var statsd = 0;
var ips = config.get('ips');

console.log('Loading on IPs: ' + ips);

function onRequest(req, res) {

    var queryData = url.parse(req.url, true).query;

    var ip = ips[Math.floor(Math.random() * ips.length)];

    //console.log('Proxying on ip: ' + ip + ' -- ' + decodeURIComponent(req.url));

    if (queryData.url) {
        counter++;
        statsd++;

        var headers = Object.assign({}, config.get('headers')[0]);

        //console.log('Proxying on ip: ' + ip + ' -- ' + queryData.url);	
        if (req.headers && req.headers.authorization) {
            headers.authorization = req.headers.authorization;
        }
        if (req.headers['x-api-key']) {
            headers['x-api-key'] = req.headers['x-api-key'];
        }

        var internalRequest = request({
            url: queryData.url,
            family: 6,
            localAddress: ip,
            headers: headers,
            time: true
        });
        res.setHeader('Access-Control-Allow-Origin', '*');
        res.setHeader('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
        res.setHeader('Access-Control-Allow-Headers', 'Content-Type');

        internalRequest
            .on('error', function(e) {
                console.log('error: ' + e);
                res.statusCode = 500;
                res.end('error 500: ' + e);
            })
            .pipe(res);

    } else {
        //res.end('No url found');
        res.end('loaderio-1e4ac91768b2952d177a51207bc4e3ac');
    }
}

var metric = probe.metric({
    name: 'Requests',
    value: function() {
        return counter;
    }
});

var last = 0;
var timer = setInterval(function() {
    client.increment('proxy_request', statsd - last);
    last = statsd;
}, 1000);