var mongodb = require("mongodb");

var url = 'mongodb://localhost:27017'

var instrumenter = mongodb.instrument();

var db;
var adminDb;
var cursor;
var cursorCountBefore;
var cursorCountAfter;

mongodb.MongoClient.connect(url)
  .then(connection => {
    db = connection;
    admindb = db.admin();
    collection = db.collection('MyCollection');

    // make sure collection has records (more than 2)
    return collection.insertMany([
      {a : 1}, {a : 2}, {a : 3}
    ]);
  })
  .then(() => {
    // get number of cursors before
    return admindb.serverStatus();
  })
  .then(result => {
    cursorCountBefore = result.cursors.clientCursors_size;

    cursor = collection.find({}).limit(2);

    // the issue is not there without the limit call
    // cursor = collection.find({})

    return cursor.toArray();
  })
  .then(arr => {
    return cursor.close();
  })
  .then(() => {
    // get number of cursors after
    return admindb.serverStatus();
  })
  .then(result => {
    cursorCountAfter = result.cursors.clientCursors_size;

    console.log(cursorCountBefore);
    console.log(cursorCountAfter);
  })
  .catch(err => {
    console.log('error: ' + err);
  })