mongodb 重复执行问题

var MongoClient = require('./node_modules/mongodb').MongoClient

var http = require('http'); var db = null;

MongoClient.connect('mongodb://127.0.0.1:27017/lbs', function(err, database) {

if(err) throw  err;
db = database;
server.listen(1234);

})

var server =http.createServer(function(req,res){ //console.log(db); db.eval('locate(118,24)',function(err,xx){ console.log("123"+xx); //res.write(xx); res.end(xx);

});

});

 console.log("123"+xx); 会打印两次，怎么回事