Stop request during file upload in NodeJs - file-upload

Question

I'm write an image uploader, and I want to constrain the size of the image to under 3mb. On the server side, I can check the size of the image in the header, something like this (using express):
app.post('/upload', function(req, res) {
if (+req.headers['content-length'] > 3001000) { // About 3mb
// Do something to stop the result
return res.send({'error': 'some kind of error'});
}
// Stream in data here...
}
I tried to stop the req by (and permuations of)
req.shouldKeepAlive = false;
req.client.destroy();
res.writeHead(200, {'Connection': 'close'});
res.end()
None of them really "destroys" the request to prevent more data being uploaded.
req.client.destroy() seem to freeze the download, but the res.send({error... is not being sent back.
Help!

Answer 1

Throw an error and catch it. It will stop the file upload, allowing you to send a response.
try { throw new Error("Stopping file upload..."); }
catch (e) { res.end(e.toString()); }
It's a bit hackish, but it works...

Answer 2

Here is my solution:
var maxSize = 30 * 1024 * 1024; //30MB
app.post('/upload', function(req, res) {
var size = req.headers['content-length'];
if (size <= maxSize) {
form.parse(req, function(err, fields, files) {
console.log("File uploading");
if (files && files.upload) {
res.status(200).json({fields: fields, files: files});
fs.renameSync(files.upload[0].path, uploadDir + files.upload[0].originalFilename);
}
else {
res.send("Not uploading");
}
});
}
else {
res.send(413, "File to large");
}
And in case of wasting client's uploading time before get response, control it in the client javascript.
if (fileElement.files[0].size > maxSize) {
....
}