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I'm getting the expected image with this code but it does not display in my pug template, instead it displays in the browser devtools console (i hope that makes sense), and it appears that I'm trying to set headers twice. My code produces [ERR_HTTP_HEADERS_SENT] as shown below.

I've read through numerous StackOverflow questions on this, including this thorough breakdown of the issue:

Error: Can't set headers after they are sent to the client

and I think what is actually happening is that I'm not correctly handling a callback, but I'm not sure.

I've really struggled with this and could use a little help pointing out where I'm going wrong.

route.js:

router.get('/issue/filedisplay/:id', issue_controller.file_display);

controller.js:

// controller.js
    exports.file_display = function(req, res) {
      gfs.files.findOne(
        { _id: mongoose.Types.ObjectId(req.params.id) },
        (err, file) => {
          //res.contentType(file.contentType);
          // Check if file
          if (!file || file.length === 0) {
            return res.status(404).json({
              err: 'No file exists',
            });
          }
          const readstream = gfs.createReadStream(file._id);
          readstream.pipe(res);
          readstream.on('close', () => {
            res.render('filedisplay', {
              title: 'Display Image',
              file: file._id,
            });
          });
          //return res.json(file);
          //return res;
        }
      );
    };

Pug Template:

//-filedisplay.pug
extends layout

block content
  h1= title
    p Display Image
    div
      img.image(src="/list/issue/filedisplay/" + file alt="")

The error:

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:482:11)
    at ServerResponse.header (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/response.js:771:10)
    at ServerResponse.send (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/response.js:170:12)
    at done (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/response.js:1008:10)
    at Object.exports.renderFile (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/pug/lib/index.js:421:12)
    at View.exports.__express [as engine] (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/pug/lib/index.js:464:11)
    at View.render (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/view.js:135:8)
    at tryRender (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/application.js:640:10)
    at Function.render (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/application.js:592:3)
    at ServerResponse.render (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/response.js:1012:7)
    at /home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/app.js:82:7
    at Layer.handle_error (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/router/layer.js:71:5)
    at trim_prefix (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/router/index.js:315:13)
    at /home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/router/index.js:335:12)
    at next (/home/don/dev/sandbox/fileupload-ex/file-upload-gridfs/node_modules/express/lib/router/index.js:275:10)
dlw
  • 19
  • 5

1 Answers1

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This issue is closed. It is not resolved and the code is still broken. Of the above controller code, all I really needed was everything down to:

readstream.pipe(res);

That works because I added target="_blank" to the referring link causing the rendered image to open in a new browser window, which was what I was actually going for. So rendering the image in a new pug template was an unnecessary step, and it is that rendering code inside the "on" method that was causing the problem.

dlw
  • 19
  • 5