Question

I have been trying to implement a RESTFul API with NodeJS and I use Mongoose (MongoDB) as the database backend.

The following example code registers multiple users with the same username when requests are sent at the same time, which is not what I desire. Although I tried to add a check!

I know this happens because of the asynchronous nature of NodeJS, but I could not find a method to do this properly. It looks like “findOne” method immediately returns, causing registerUser to return and then another request is processed.

By the way, I don’t want to check for existing users with a separate API function, I need to check at the registration stage. Is there any way to do this?

Controller.prototype.registerUser = function (req, res) {
    Users.findOne({'user_name': req.body.user_name}, function(err, user) {
        if(!user) {
            new User({user_name: req.body.user_name}).save(function(err) {
                if(!err) {
                    res.send("User saved");
                } else {
                    res.send("DB Error: Could not save user!");
                }
            });
        } else {
            res.send("User exists");
        }
    });
}

Answer 1

You should consider setting the user_name to be unique in the Schema. That would ensure that the user_name stays unique even if simultaneous requests are made to set an identical user name.