Why does this request to Node server hang?

Question

I am very new to express and node. I was trying to upload an image using multiparty and code given here. I have put a check for file size. When I upload a file of size greater than the limit it lands in the "problem section". The problem is the server hangs and responds back only after request timeout. I have tried many solution on stack overflow but nothing seems to work. It works if the file size is below the limit. I am very sure that the code reaches the problem section and there is no problem with the upload logic. But it seems that I have to do something in the "problem section". Please tell me what am I missing.

I have replaced the code in the problem section with next(), res.send(), res.end(), next(err), return; but It does not work. It hangs no matter what.

Following is the code:

router.post("/image", function(req, res, next) {
  if(req.user) {
    upload.uploadToS3(req, S3_BUCKET, S3_PROFILE_IMAGE_FOLDER, function(result) {
      if(result.error != null && result.error === false) {
        models.Customer.update({
          orignalImage : result.fileLocation
        },{
          where : { mobileNumber : req.user.mobileNumber}
        }).then(function(customer) {
          if(customer) {
            res.send({
              url: result.fileLocation,
              error : false
            });
          } else {
            res.status(400);
            res.send({error : true,
              error_message : 'Image upload failed'});
          }
        });
      } else {
        //PROBLEM SECTION
        res.status(404);
        res.json({error : true, error_message : result.error_message});
      }
    });
  } else {
    res.status(403);
    res.send({message: "access denied"});
  }
});

response after timeout

Please tell me if you need more details I will upload it. var uploadToS3 = function(req, S3_BUCKET, folder, callback) { var s3Client = knox.createClient({ secure: false, key: awsConfig.accessKeyId, secret: awsConfig.secretAccessKey, bucket: S3_BUCKET, });

  var headers = {
    'x-amz-acl': 'public-read',
  };

  var form = new multiparty.Form();
  var batch = new Batch();

  batch.push(function(cb) {
    form.on('part', function(part) {
      var validity = validateFile({type : part.headers['content-type'], name : part.filename, length : part.byteCount});
      console.log(validity);
      if(validity.isValid) {
        cb(null, { filename : folder+"/"+generateFileName({name : part.filename}), part : part});  
      } else {
        cb({error : true, error_message : validity.reason, part:part }, "advra kedavra");
      }
    });
  });

  batch.end(function(err, results) {

    if (err) {
      console.log(err);
      err.statusCode = 200;
      callback(err);
    } else {
      form.removeListener('close', onEnd);
      var result = results[0];
      var part = result.part;
      var destPath = result.filename;
      var counter = new ByteCounter();
      part.pipe(counter); // need this until knox upgrades to streams2
      headers['Content-Length'] = part.byteCount;
      s3Client.putStream(part, destPath, headers, function(err, s3Response) {
        result = {};
        if(err) {
          console.log(err);
          result.error = true;
          result.error_message = "Problem in uploading!";
        } else {
          console.log(s3Response.req.url);
          result = {error: false, statusCode : s3Response.statusCode, message : "file upload successful.", fileLocation : s3Response.req.url};
        }   
        callback(result);
      });
      part.on('end', function() {
        console.log("File upload complete", counter.bytes);
      });
    }
  });
  function onEnd() {
    console.log("no uploaded file");
    callback({error:false, error_message:"no uploaded file."});
  }
  form.on('error', function(err) {
    console.log('Error parsing form: ' + err.stack);
  });
  form.on('close', onEnd);
  form.parse(req);
}

Answer 1

After a 3 day long search for the answer I found one answer. Express.js close response

The problem section should be the following :

res.status(400);
res.set("Connection", "close");
res.json({error:true, error_message : "<some - error message>"});

Answer 2

You should simply add a .end() after setting the status as: res.status(400).end();

See official docs

res.end([data] [, encoding])

Ends the response process. This method actually comes from Node core, specifically the response.end() method of http.ServerResponse.

Use to quickly end the response without any data. If you need to respond with data, instead use methods such as res.send() and res.json().

res.end();

res.status(404).end();

Answer 3

    res.status(400);
    res.set("Connection", "close");
    res.json({error:true, error_message : "<some - error message>"});

I am not sure that solves your issue. The 'problem section' is in your callback, which would only run after the upLoadToS3 function runs. The 'problem' is probably with that function. You might have to refactor that to handle large file uploads.