const url = 'mongodb://localhost:31000/test?replicaSet=rs';

MongoClient.connect(url, (err, client) => {
  if (err) return console.dir(err);

  let db = client.db();
  let cursor = db.collection('test').find({});
  let time = new Date().getTime();
  cursor.count((err, result) => {
    let stream = client.db().collection('test').watch([], { fullDocument: 'updateLookup' });
    console.log('watching...');
    stream.on('change', change => console.dir(change));
    stream.on('error', err => {
      let errTime = new Date().getTime();
      console.log(`error occured at: ${(new Date()).toISOString()}, in: ${errTime - time}ms`);
      console.dir(err);
      client.close();
    });
  });
});