Mongodb Aggregation Cursor With Nodejs Driver

I am using MongoDB v3.2 and I'm using the native nodejs driver v2.1. When running the aggregation pipeline on large data sets(1mil+ documents), I am encountering the following erro

Solution 1:

Ok I figured it out. It was not working because I was passing in a callback function as the last parameter in the aggregate method. By passing null, it allowed the stream to work as expected. Changes shown below:

var cursor = eventCollection.aggregate([
            {
                $match: {
                    event_type_id: {$eq: 89012}
                }
            },
            {
                $group: {
                    _id: "$user_id",
                    score: {$sum: "$points"}
                }
            },
            {
                $sort: {
                    score: -1
                }
            }
        ],
        {
            cursor: {
                batchSize: 500
            },
            allowDiskUse: true,
            explain: false
        }, null);