Why response is closed and not finished?

Question

I have the following code in node.js in a function readFile:

      res.setHeader("content-type", 'application/octet-stream');
      res.setHeader("Content-Disposition", 'attachment; filename="' + 'original' + '"' + "; filename*=UTF-8''" + 'original' + "");
      var readStream;
      var exists = fs.existsSync(fullPath);
           if (exists) {
                callback(true);
                readStream = fs.createReadStream(fullPath);
                readStream.pipe(res);
           } else {
                callback(false);
                return;
           }
              res.on('finish', function(){
                        logger.info('response ending');
                        readStream.close();
               })
              res.on('close', function(){
                        logger.info('response close');
                        readStream.close();
              })
              res.on('error', function(error){
                        logger.info(error);
                        readStream.close();
              })

For some reason, some requests are emitted the close event, while other the finish. As I understand, close is emitted when something get wrong.

The close event can fired between 2 sec and up to 2 min. In rare cases, no close and no finish events are emitted and all, and the request is "stuck", waiting for a response.

What can be the reason that some requests will success, and other not?

EDIT

How can I know why a close event has emitted? Is it a client issue or a bug in my application?

Answer 1

if there is a finish then it is all normal, but if there is a close then it could be because of anything. I tried following code following to your event declarations, before the pipe was completed.

1. `res.emit('close');`  And
2. `readStream.close();`

Now the first one here explicitly emits the close event, and the second one closes the readStream which was piped. both of these statements cause to trigger the res.on('close'), But I couldn't really find the reason for close.

I can not be sure if it is a server bug or client bug , but there could be following reasons:

1. res.emit('close'); explicitly emitted the close event.

2. something went wrong with source of pipe. (ex. in above case #2 the readStream was closed) in this case it would take a little longer than the rest of the reasons.

3. Network went down after the response sending was started

4. client can also cause the close event to trigger , if it requested the data and then afterwards client wasn't present to receive the data.

the reason could be anything, which made the response not to complete.

Answer 2

i think this comes from the HTTP protocol itself. there is a option for keep-alive. if this is used then the connection can be reused for different requests.

you shut disable it with res.set("Connection", "close"); ant test it again.

Answer 3

i would prefer ending your response when the close and finish event is called rather than closing the readStream.

  res.setHeader("content-type", 'application/octet-stream');
  res.setHeader("Content-Disposition", 'attachment; filename="' + 'original' + '"' + "; filename*=UTF-8''" + 'original' + "");
  var readStream;
  var exists = fs.existsSync(fullPath);
       if (exists) {
            callback(true);
            readStream = fs.createReadStream(fullPath);
            readStream.pipe(res);
       } else {
            callback(false);
            return;
       }
          res.on('finish', function(){
                    logger.info('response ending');
                    readStream.close(); // This closes the readStream not the response
                    res.end('FINISHED');  // Ends the response with the message FINISHED

           })
          res.on('close', function(){
                    logger.info('response close');
                    readStream.close(); // This closes the readStream not the response
                    res.end('CLOSED'); // Ends the response with the message CLOSED

          })
          res.on('error', function(error){
                    logger.info(error);
                    readStream.close(); // This closes the readStream not the response
                    res.end(error); // Ends the response with ERROR
          })

The response is not closed since you close the readStream which closes the readStream alone and not the response. To finish or end the response use res.end().

Reference: http://nodejs.org/api/http.html#http_event_close_1 http://nodejs.org/api/http.html#http_response_end_data_encoding

Hope this helps.