Poll the nextbus api and log entries into a mongodb database

poll_nextbus.js

var http = require('http');
var xml2js = require('xml2js');
var mongodb = require('mongodb')
   
// get mongdb handle 
var db = new mongodb.Db('test', new mongodb.Server("127.0.0.1", 27017, {}))

// keep track of the last time we got a response from nextbus
var lastTime = 0;

// setInterval callback
function createPollNextbusCallback(coll) {
  var pollNextbus = function(){
    var parser = new xml2js.Parser()

    var options = {
      host:'webservices.nextbus.com',
      path:'/service/publicXMLFeed?command=vehicleLocations&a=sf-muni&t='+lastTime
    }

    var req = http.request( options, function(res){
      var data = "";

      res.setEncoding('utf8');

      res.on('data', function (chunk) {
        data += chunk;
      });

      res.on('end', function () {
        try{
          parser.parseString( data, function( err, result ){

            if( !result || !result.hasOwnProperty('body') ){
              return;
            }

            lastTime = Number( result.body.lastTime[0].$.time );

            if( result.body.hasOwnProperty('vehicle') ){
              var vehicles = result.body.vehicle;
              console.log( vehicles.length + " vehicles" );

              for(var i=0; i<vehicles.length; i++){
                vehicle = vehicles[i].$;
                vehicle.time = lastTime;
                if( vehicle.hasOwnProperty('lat') && vehicle.hasOwnProperty('lon') ){
                  vehicle.loc = [Number(vehicle.lat),Number(vehicle.lon)];
                  vehicle.lat = Number(vehicle.lat);
                  vehicle.lon = Number(vehicle.lon);
                }

                coll.insert( vehicle );
              }
            }

            console.log( "lastTime: " + lastTime );
            console.log( "---" );
          });
        } catch( err ) {
          console.log( "exception caught: "+err );
        }

      });
    });

    req.end()

    req.on('error', function(e) {
      console.time( "something went wrong with the request: " + e.message );
    });
  }

  return pollNextbus
}

db.open( function( err, p_client ) {
  var coll = db.collection( "nextbus_geoms" );
  setInterval( createPollNextbusCallback(coll), 2000 );
});