Transaction auto-monitoring on MongoDB not working with promises

Description

When using callbacks, transaction times are correctly reported on MongoDB operations, but these are not shown when using the promise implementation.

Either of these is working:

function withMongoose() {
    return mongoose.model(x).find(query).lean();
}

function withCallbacks() {
    return new Promise((resolve, result) => {
        mongo.db.collection('x').find(query).toArray((err, res) => {
            if (err) {
                reject(err);
                return;
            }
            resolve(res);
        });
    });
}

However this is not working:

function withPromises() {
    return mongo.db.collection('x').find(query).toArray();
}

Here’s what it looks like when we switched from mongoose (withMongoose) to native driver promises (withPromises):

Expected Behavior

I expect the same result with the three methods above.

Steps to Reproduce

See code snippets.

Your Environment

NewRelic: 7.5.1 MongoDB (driver): 3.6.4 Mongoose: 5.11.17 Node: 14.16.0

[bizob2828]

Ok I think I have a fix. This looks better

I will open a PR and get it reviewed by the team

[bizob2828]

Thanks for the code snippet @richardgarnier! I can reproduce. I’m still new on the Node.js agent team but I think the issue is that the mongodb instrumentation isn’t built to support toArray not having a callback. I will start working on a fix later today and open a PR against this. Thanks for submitting the issue and bringing it to our attention! If you can keep the code snippet where you wrap the call in a native Promise that would be a good workaround for the moment.