socket.io-stream write file to disc then when finished emit file path

Question

I have a problem using socket.io-stream, when I send file from client to server. I push file path to mongodb and then save the file to a file-folder. The problem is that while disc is writing the file, the file path is returned to the client before the writing has complete and then the img element paht is correct but the image does not render on the page.

The code belowe works as expected but im manually waiting 100ms and then returning the path to the client. Which does not garantee if image is too big this 100ms will do the trick. Any other solutions ?

Server side:

ss(socket).on('fileUpload', function(stream, data) {
        Chat.findByIdAndUpdate(data.roomId, {
            $push: {
                "messages": {
                    author: data.author,
                    date: Date.now(),
                    isFile: true,
                    extension: data.extension
                }
            }
        },{safe: true, new: true, upsert: true}, (err, message) => {
            if(err){
                console.log(err);
            }

            let msg = message.messages[message.messages.length - 1];
            let filename = path.join(__dirname, 'public/files' , `${msg._id}.${msg.extension}`);
            stream.pipe(fs.createWriteStream(filename));
            setTimeout(() => {
                io.sockets.to(data.roomId).emit('chat-connection', msg);
            },100);
        });
    });

Client Side:

function fileUpload(file) {

        let fileExtension = file.name.split('.').pop();
        let stream = ss.createStream();
        // upload a file to the server.
        ss(vm.socket).emit('fileUpload', stream,
            {
                size: file.size,
                extension: fileExtension,
                roomId:vm.chatInstance._id,
                author:$scope.user.fullName,
            });
        ss.createBlobReadStream(file).pipe(stream);
    }

Answer 1

You can check for the finish event on the stream you're writing to.

stream.on('finish', () => {
    io.sockets.to(data.roomId).emit('chat-connection', msg);
});
stream.pipe(fs.createWriteStream(filename));