node.js, callback on the end of an http-proxy request? - node.js

Question

I'm trying to learn node.js, and my context is the http-proxy module from nodejitsu.
I'd like to get access to the end of the proxy event, so that I can log how long the target server took to respond. However, I can't out how to create the appropriate callback or event handler. I've looked at the source for http-proxy, and it doesn't seem to take the conventional callback method.
Here's a sample, I'm sure its a simple fix to someone that breaths Node:
/* demonstrate a basic proxy server that can log the time
it takes to execute a given hit on the destination server
*/
var http = require('http'),
httpProxy = require('http-proxy');
// Create the proxy server
httpProxy.createServer(function (req, res, proxy) {
var startTime = ( new Date()).getTime();
// NEED HELP HERE.
// something like this should do it?
proxy.addListener("end",function() {
var endTime = (new Date()).getTime();
console.log("request took " + (endTime - startTime) + "ms");
});
proxy.proxyRequest(req, res, {
host: 'localhost',
port: 9000
});
}).listen(8000);
// the destination server
http.createServer(function (req, res) {
res.writeHead(200, { 'Content-Type': 'text/plain' });
res.write('request successfully proxied: ' + req.url +'\n' + JSON.stringify(req.headers, true, 2));
// make the hit slow by pausing the end()
setTimeout(function() {
res.end();
},2000);
}).listen(9000);

Answer 1

One approach is to intercept the res.end() call. I have like 3 days of express experience, so I don't know what this will screw up:
var proxy = new httpProxy.RoutingProxy();
app.get("/foo", function (req, res) {
var realEnd = res.end;
var start = +new Date();
res.end = function () {
var elapsed = +new Date() - start;
console.log("elapsed", elapsed);
realEnd.apply(res);
}
proxy.proxyRequest(req, res, {
host: 'localhost',
port: 9000
});
});