Multer file upload error, request hanging

Question

I have never written a question before, because I have always found an answer here to my issues prior to asking. However I am struggling with a fileFilter function on a file upload POST route on express. I have used the multer upload function in the route, and also as middleware, with an error handling middleware following, and cannot get it to behave as I expect.

I am expecting the 'LIMIT_UNEXPECTED_FILE' error to trigger a flash message, and then a redirect to the same page where the file upload is being chosen. This happens sometimes, but is not consistent. If multiple upload attempts fail in a row during my testing, the third or fourth time the request will hang.

I know the fileFilter function is running, and outputs the correct error, because I have multiple console.logs in my upload function inside the post route, and it outputs the correct error. The problem is the req.flash and then res.redirect are not getting triggered.

When I was using the upload function as middleware in the post route, and then another middleware function after the post route to handle the error, I was also having issues with the res.redirect not triggering. Not sure what I'm missing here?

index.js


// set upload destination and filename for uploads
const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    cb(null, './public/uploads/');
  },
  filename: (req, file, cb) => {
    const {
      originalname
    } = file;
    cb(null, `${uuid()}-${originalname}`);
  },
});


// filter by file types uploaded
const fileFilter = (req, file, cb) => {
  console.log(file.mimetype);
  if (file.mimetype.split('/')[0] === 'image') {
    cb(null, true);
  } else {
    cb(new multer.MulterError('LIMIT_UNEXPECTED_FILE'), false);
  }
};

const upload = multer({
  storage,
  fileFilter,
  limits: {
    fileSize: 5 * 1024 * 1024
  }
}).single('document');


// Upload route - logged in
router.post('/app/admin/upload', function(req, res) {

  if (req.isAuthenticated()) {
    console.log('testing1');
    upload(req, res, (err) => {
      if (err) {
        console.log(err.code);
        if (err.code === 'LIMIT_FILE_SIZE') {
          req.flash('docError', 'File upload failed due to file size');
          res.redirect('back');
        } else if (err.code === 'LIMIT_FILE_COUNT') {
          req.flash('docError', 'File upload failed due to file count');
          res.redirect('back');
        } else if (err.code === 'LIMIT_UNEXPECTED_FILE') {
          console.log('testing2');
          req.flash('docError', 'File upload failed due to file type');
          res.redirect('back');
        } else {
          console.log(err.code);
          req.flash('docError', 'File upload failed due to unknown error');
          res.redirect('back');
        }
      } else {
        if (!req.file) {
          req.flash('docError', 'No file chosen to upload');
          res.redirect('back');
        } else {
          req.flash('docSuccess', 'File uploaded successfully');
          res.redirect('back');
        }
      }
    });

  } else {
    res.redirect('/');
  }
});

Server console output when triggering upload post route

[nodemon] restarting due to changes...
[nodemon] starting `node ./bin/www`
listening on port 3000
testing12345
application/x-msdownload
LIMIT_UNEXPECTED_FILE
testing 23456

Multer file upload error, request hanging

0 Answers