NodeJS、ExpressJS、Mongoose 4.4、Nonce用于并发和Document.update

我有以下组合:NodeJS、Express、MongoDB和Mongoose。我用mongoose promises实现了一个nonce,允许并发编辑。请参见以下内容:

//schema
var item_schema = {
    //_id: {type: Schema.ObjectId, required: true},
    name: {type: String, required: true, index: { unique: true }},
    code: {type: String, required: true, index: { unique: true }},
    date_time_created: {type: Date, required: true},
    date_time_updated: {type: Date, required: true},
    nonce: {type: Schema.ObjectId}
};

//model
var item_model = mongoose.model('item', schema);

//update
var concurrency_update = function(req, res, retries) {

    var promise = model.findById(req.params.id).exec();

    var updated_nonce = mongoose.Types.ObjectId();

    promise.then(function(document){ //find document response

        if(!document) {
            res.status = 404;
            return Promise.reject( { "message" : req.params.id + ' document does not exist' } );
        }
        var now = new Date();
        if(req.body.code) {
            document.code = req.body.code;
            document.date_time_updated = now;
        }
        if(req.body.name) {
            document.name = req.body.name;
            document.date_time_updated = now;
        }
        if(!document.nonce) {
            document.nonce = updated_nonce;
            var old_nonce = document.nonce;
        }
        else {
            var old_nonce = document.nonce;
            document.nonce = updated_nonce;
        }
        return document.update({ "_id" : req.params.id, "nonce" : old_nonce }).exec();

    }).then(function(raw){ //update response

        var number_affected = raw.n;
        console.log(raw);
        if(!number_affected && retries < 10){
            //we weren't able to update the doc because someone else modified it first, retry
            console.log("Unable to update, retrying ", retries);
            //retry with a little delay
            setTimeout(function(){
                concurrency_update(req, res, (retries + 1));
            }, 20);
        } else if (retries >= 10){
            //there is probably something wrong, just return an error
            return Promise.reject({ "message" : "Couldn't update document after 10 retries in update"});
        } else {
            res.json({"message": req.params.id + ' document was update'});
        }

    }).catch(function(err){
        res.send(err.message);
    });

并发更新基于以下内容: http://www.mattpalmerlee.com/2014/03/22/a-pattern-for-handling-concurrent/

阅读猫鼬文档,更新就是基于此。 http://mongoosejs.com/docs/api.html#document_Document-update

然而,当代码进入final.then(//更新响应)时,我看到了原始的。n(numberAffected)=1但数据库从未更新?

答案可能很接近,但我错过了。 我错过了什么?