const MongoClient = require('mongodb').MongoClient;

// Default replica set options 
var replSetOpts = { 
    ha: true, 
    haInterval: 500, 
    reconnectWait: 5000, 
    poolSize: 5, 
    retries: 10000000, 
    socketOptions: { 
      connectTimeoutMS: 20000, 
      keepAlive: 1, 
      noDelay: true 
    }
};

const url = "mongodb://<user>:<pass>@primary:secondary/<datasbase>?replicaSet=<rs>"

MongoClient.connect(url, replSetOpts, function(err, db) {
  if(err) {
    console.log('Error: %s', err)
    process.exit(1)
  } 

  console.log("Connected correctly to server");
  db.listCollections().toArray(function(err, items) {
    console.log(items);
    db.close();
  });
});