Node Mongoose MongoDb and asynchronicity

Question

I've hopefully a quick question for someone with a bit more knowledge than I.

If I have code in a Node api implementation which basically creates an entity and saves it directly to MongoDB using Mongoose, do I need to wrap all that in an promise library to get it as asynchronous as possible? Or will the implementation of the Mongoose/MongoDB Node libraries already do their work in an async fashion, so that my only overhead on the message pump is the object creation.

The code below is what we have in the API, it creates the promise below and executes it, I'm just wondering if the overhead of the promise is actually worth it if the Mongoose/MongoDB libraries are async anyway.

Hope all that makes sense.

function action(promise) {
    var date = new Date(),
    taskWorkQueue = new TaskWorkQueueModel({
            "TaskId": taskid,
            "metadata": metadata,
            "State": 0,
            "TaskType": taskType,
            "ApplicationName" : token.ApplicationName ,
            "dateEntered": date});
    taskWorkQueue.save(function (err) {
        if (err)
        {
            promise.reject(err);
        }
        else
        {
            promise.resolve(taskWorkQueue);
        }

    });

Timothy Strimple · Accepted Answer · 2014-10-09 14:27:42Z

3

That is not the reason to wrap these things in a promise. All of the good node libraries (like Mongoose) are already asynchronous. Using a promise just gives you an alternative way to write your code instead of using callbacks.

Take a look at the documentation for q, they show an example of what kind of difference in coding style you can expect from promises versus callbacks.

step1(function (value1) {
    step2(value1, function(value2) {
        step3(value2, function(value3) {
            step4(value3, function(value4) {
                // Do something with value4
            });
        });
    });
});

versus

Q.fcall(promisedStep1)
.then(promisedStep2)
.then(promisedStep3)
.then(promisedStep4)
.then(function (value4) {
    // Do something with value4
})
.catch(function (error) {
    // Handle any error from all above steps
})
.done();

It's also worth mentioning that mongoose already supports promises via mpromise, and you shouldn't need to wrap them yourself. There are also libraries available which use other promise frameworks around mongoose like mongoose-q.

answered Oct 9, 2014 at 14:27

Timothy Strimple

23.1k6 gold badges73 silver badges76 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Bigtoe Over a year ago

Thanks Timothy, coming from C# async I made the mistake thinking that a promise actually runs as a separate (thread/fibre/something). I see now it is basically syntactic sugar over callbacks, giving something that looks like async based task continuations in C#. Thanks for the clarification, much appreciated.

Collectives™ on Stack Overflow

Node Mongoose MongoDb and asynchronicity

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related