CODEWITHSUNDEEP
node.jsasynchronouspromisesettimeoutcancellation
boss
boss

Reputation: 1606

Async Method Timeout in Nodejs

I am downloading a file and sometimes file size can be big and timeout is not enough. when timeout, I would like to cancel download process because even I get a timeout error, it continues to process the file and give the following exception

_http_outgoing.js:470 throw new ERR_HTTP_HEADERS_SENT('set'); ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client at ServerResponse.setHeader (_http_outgoing.js:470:11)

here is my async method

router.get('/api/files/GetFile', urlencodedParser, (req, res) => { 

 return new Promise(function (resolve, reject) {    
    (async function () {
      try {

        var folderName = "File_" + moment().format('DD-MM-YYYY HH_mm_ss');
        await routerFile.CreatePdfZip(req.query.VoucherCodes, req.query.AppNames, folderName);

        var fullzipPath = './FilesToDownload/' + folderName + '.zip';

        zipFolder('./FilesToDownload/' + folderName, './FilesToDownload/' + folderName + '.zip', function (err) {
          if (err) {
            return reject(err);
          } else {

            console.log('zip created');
            rimraf('./FilesToDownload/' + folderName, function () {
              console.log("folder has been deleted");
            });

            fs.readFile(fullzipPath, (err2, zipData) => {
              if (err2) reject(err2);

              const base64 = zipData.toString('base64');
              res.setHeader('Content-type', 'application/zip');
              res.type('zip');
              res.end(base64, 'binary');
              console.log('EXCELLENT');
            });
          }
        });       
      } catch (error) {    
        return reject(error);
      }
    })();
    }).catch(error => {
      console.log(error);
      res.send(error);
   });
});

The error occurs in the line res.setHeader('Content-type', 'application/zip');

PS: router variable comesfrom const router = express.Router();

and here is the timeout set

const app = express();
app.use(timeout('2s'));
app.use(bodyParser());
app.use(haltOnTimedout);
app.use(cookieParser());
app.use(haltOnTimedout);

function haltOnTimedout(req, res, next) {
  if (!req.timedout)
    next();
  else {
    console.log('TIMEOUT.----------------------------------------------');    
  }
}

What am I doing wrong here? Or is there better way to set a timeout and cancel the downloading process

PS: CreatePdfZip method takes time.

Upvotes: 0

Views: 317

Answers (1)

Sagar Chilukuri
Sagar Chilukuri

Reputation: 1448

To avoid this error, you can check if the response is already sent and sent the response only if not sent (But does not really solve/cancel download processing)

...
fs.readFile(fullzipPath, (err2, zipData) => {
    if (err2) reject(err2);

    if (!res.headersSent) {
        const base64 = zipData.toString('base64');
        res.setHeader('Content-type', 'application/zip');
        res.type('zip');
        res.end(base64, 'binary');
        console.log('EXCELLENT');
    }
});
...

Doc Link

Upvotes: 1

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