https://github.com/nodejs/io.js/issues/2308

memory-leak.js

var http = require('http');
var streamifier = require('streamifier');
var Busboy = require('busboy');
var FormData = require('form-data');
var PORT = 6666;
var data = new Buffer(100 * 1024 * 1024);

http.createServer(function(req, res) {
  var busboy = new Busboy({headers: req.headers});
  busboy.on('file', function() {
    console.log('uploaded:', mb(data.length),' - memory used:', mb(process.memoryUsage().rss));
    setTimeout(upload, 1000);
  });
  req.pipe(busboy);
}).listen(PORT, '127.0.0.1', upload);

function upload() {
  var form = new FormData();
  form.append('file', streamifier.createReadStream(data), {
    filename: 'upload',
    contentType: 'application/octet-stream',
    knownLength: data.length
  });
  form.submit('http://127.0.0.1:' + PORT);
}

function mb(val) {
  return Math.round(val / (1024 * 1024)) + " MB";
}

Should fix it, or?

busboy.on('file', function(fieldname, stream) {
    stream.resume();
    console.log('uploaded:', mb(data.length),' - memory used:', mb(process.memoryUsage().rss));
    setTimeout(upload, 1000);
  });

@skomsi: Good find, it seems to solve the leak. It's kind of obvious now that the data is lost in that unconsumed stream, thanks!