proxy_with_balance_file.js

var fs = require('fs'),
   sys = require('sys'),
  http = require('http');

http.createServer(function (req, res) {
  checkBalanceFile(req, res);
}).listen(8000);

function checkBalanceFile(req, res) {
  fs.stat("balance", function(err) {
    if (err) {
      setTimeout(function() {checkBalanceFile(req, res)}, 1000);
    } else {
      passThroughOriginalRequest(req, res);
    }
  });
}

function passThroughOriginalRequest(req, res) {
  var request = http.createClient(2000, "localhost").request("GET", req.url, {});
  request.addListener("response", function (response) {
    res.writeHeader(response.statusCode, response.headers);
    response.addListener("data", function (chunk) {
      res.write(chunk);
    });
    response.addListener("end", function () {
      res.close();
    });
  });
  request.close();
}

sys.puts('Server running at http://127.0.0.1:8000/');