Resolving backpressure manually in node.js

gistfile1.js

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

var server = http.createServer(function(request, response) {
  var file = fs.createWriteStream('upload.jpg'),
      fileBytes = request.headers['content-length'],
      uploadedBytes = 0;
    
  request.on('data', function(chunk) {
    uploadedBytes += chunk.length;
    var progress = (uploadedBytes / fileBytes) * 100;
    response.write('progress: ' + parseInt(progress, 10) + '%\n');

    var bufferOK = file.write(chunk);

    if (!bufferOK) {
      request.pause();
    }
  });

  file.on('drain', function() {
    request.resume();
  });

  request.on('end', function() {
    response.end('upload complete\n');
  });

});

server.listen(8080);