NodeJS Listening to RethinkDB changes

rethink_geo_app.js

var r = require('rethinkdb'),
    _ = require('lodash');

var debug = process.env.DEBUG || false;

var dbConfig = {
    host: process.env.RDB_HOST || 'localhost',
    port: parseInt(process.env.RDB_PORT) || 28015,
    db  : process.env.RDB_DB || 'geo',
    tables: {
        'locations': 'id'
    }
};

var connection = null;
var connected = r.connect(dbConfig);

connected
    .then(function(conn) {
        connection = conn;
        listen_changes();
    })
    .error(function(error) {
        console.log(error);
    })
;


var listen_changes = function() {
    r.table('locations').changes().run(connection, function(err, cursor) {
        if (err) throw err;
        cursor.each(function(err, row) {
            if (err) throw err;

            var new_pos = true;
            var device_location = row.new_val;
            if(!_.isUndefined(row.old_val)) {
                new_pos = row.old_val.latitude != device_location.latitude ||  row.old_val.longitude != device_location.longitude
            }


            if(new_pos) {
                console.log(device_location.id +': '+ device_location.protocol +
                    ' lat:' + device_location.latitude +
                    ' lon:' + device_location.longitude +
                    ' address: ' + device_location.address

                );
            }

            if(debug) {
                console.log(JSON.stringify(row, null, 2));
            }
        });
    });
};