Multer: Multer silent crash on uploading

[Saishy]

When trying to upload a file of 143KB I receive the following error:

Bad Gateway

The proxy server received an invalid response from an upstream server.
Apache/2.4.10 (Debian) Server at 50.116.34.26 Port 80

When trying to upload a file of 4KB I receive one of the two, randomly:

Proxy Error

The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request POST /grimoireworks/admin/uploads/uploadimage.

Reason: Error reading from remote server

or

Service Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.
Apache/2.4.10 (Debian) Server at 50.116.34.26 Port 80

this is the code I'm using on the route:

app.post('/admin/uploads/uploadimage',
    ajaxAdminLoggedIn,
    upload.single('image_file'),
    function(req, res, next) {
        console.log("start of upload");

        req.socket.setTimeout(10000);

        var supportedTypes = ['image/jpeg', 'image/png', 'image/gif'];
        var type = req.file.mimetype;//mime.lookup(req.files.image_file.path);

        console.log("before supportedTypes check");

        if (supportedTypes.indexOf(type) == -1) {
            fs.unlink(req.file.path);
            return res.send(415, 'Supported image formats: jpeg, jpg, jpe, gif, png.');
        }

        console.log("before targetPath");

        var targetPath = __dirname + '/public/images/';
        if (req.body.image_type == "wizard") {
            targetPath += 'classes/';
        } else if (req.body.image_type == "spell") {
            targetPath += 'spells/';
        } else {
            fs.unlink(req.file.path);
            return res.send(415, 'Invalid image type.');
        }

        console.log("before tempPath");

        var tempPath = req.file.path;

        console.log("before createReadStream");

        var source = fs.createReadStream(tempPath);
        var dest = fs.createWriteStream(targetPath + req.file.originalname);

        console.log(tempPath);
        console.log(targetPath + req.file.originalname);

        source.pipe(dest);

        console.log("after pipe");

        source.on('error', function(err) {
            if (err) {
                return res.send(500, 'Something went wrong');
            }
        });

        source.on('end', function() {
            //delete file from temp folder
            fs.unlink(tempPath, function(err) {
                if (err) {
                    return res.send(500, 'Something went wrong');
                }

                res.redirect('back');
            }); //#end - unlink
        }); //#end - on.end
    }
);

This is the form

<form action="<%= relativePath %>/admin/uploads/uploadimage" method="post" enctype="multipart/form-data">
                            <div class="form-group">
                                <p>Select the type of the image:</p>
                                <label>
                                    <input type="radio" name="image_type" id="image_type_wizard" value="wizard" checked>
                                    Wizard
                                </label>
                                <br>
                                <label>
                                    <input type="radio" name="image_type" id="image_type_spell" value="spell">
                                    Spell
                                </label>
                            </div>
                            <div class="form-group">
                                <label for="image_file">Select your image:</label>
                                <input type="file" name="image_file" id="image_file" />
                                <p class="help-block">Supported files: jpg, jpeg, gif, png.</p>
                            </div>
                            <div class="text-right">
                                <button type="submit" class="btn btn-success">Submit</button>
                            </div>
                        </form>

Besides this multer is just using this:

var bodyParser = require( 'body-parser' );
var multer  = require('multer');

No logs appear anywhere, the node application restarts when trying to upload a file.

Apache just shows:

[Sun Apr 16 22:40:11.299511 2017] [proxy_http:error] [pid 29899] (20014)Internal error: [client 189.35.245.253:7512] AH01102: error reading status line from remote server 127.0.0.1:6161, referer: http://50.116.34.26/grimoireworks/admin/uploads
[Sun Apr 16 22:40:11.527747 2017] [proxy:error] [pid 29900] (111)Connection refused: AH00957: HTTP: attempt to connect to 127.0.0.1:6161 (127.0.0.1) failed
[Sun Apr 16 22:40:11.527800 2017] [proxy:error] [pid 29900] AH00959: ap_proxy_connect_backend disabling worker for (127.0.0.1) for 60s
[Sun Apr 16 22:40:11.527806 2017] [proxy_http:error] [pid 29900] [client 189.35.245.253:7519] AH01114: HTTP: failed to make connection to backend: 127.0.0.1, referer: http://50.116.34.26/grimoireworks/admin/uploads

[sahandnayebaziz]

Currently debugging the same thing. Thought it had something to do with cors initially, but seeing the same failure when deployed on AWS Elastic Beanstalk with and without cors.

[jdhollander]

I too have the same thing, using nginx proxy and getting a 502 error each time.

EDIT: Nope, nothing to do with multer. I was getting an error elsewhere and PM2 was restarting the app without recording the error, thus making it look like a silent failure.

[iLyxa3D]

PM2 was restarting the app without recording the error, thus making it look like a silent failure.

Same problem..

[sahandnayebaziz]

For the record, my problem was in my nginx config! Not an issue with express for me. Maybe something you can check in Apache config?

[iLyxa3D]

For the record, turns out, there was no crash :) PM2 watched the changes in the folder and rebuild the application automatically - looks like crash restarting without error log.
Excluding the download folder from the list of the watch (pm2 ... --ignore-watch "folder_name") stoped restarting.

[LinusU]

It seems like this is quite common, and it has happened to me as well. Be sure to take care when using nodemon, pm2, etc.

@Saishy feel free to reopen if you think that the problem was not nodemon/pm2/etc.

[ayanth]

@iLyxa3D Thank you so much! Been digging around to resolve this issue for a while. So many technologies.. so many different possiblities.

But in the end it was all from watch.

Thank you again!

[josser]

@sahandnayebaziz Got same error, only when running multer behind nginx revers proxy. Can you please share what was the reason for you?

[ineeve]

Multer stopped working when I added an nginx reverse proxy. Can you please share your nginx configuration?

[sk1nzz]

@iLyxa3D
Big thanks! The fix was so simple… I thought the issue was caused by nginx but not PM2.