Question

I am new to nodejs but I did get something to work last night with mongodb on a IIS server with iisnode. 🙂

But I am wondering over one thing which seems to be a refresh bug or something.
When I go to “http://localhost/mongo.js” in my browser the results will just be “[]” the first time. If I hit refresh the results will be what I expected (an json array with persons). Dosen’t this seems wrong?

Let’s say now I do it with a query, “http://localhost/mongo.js?name=Daniel”, and get all Persons with the name Daniel. The response the first time will be “all the persons” because that’s what we asked for above, and when I hit refresh the results will be all the Persons named Daniel. Why is this happening?
It seems that the server cached the query’s i’ve made, and I don’t want to hit refresh everytime to get the correct results.

This is my code I am using: (also available here http://pastebin.com/PnVfrQmh)

/* GLOBALS
----------------------------------------------------------------------*/
var rdata = [];

/* SERVER SETTINGS
----------------------------------------------------------------------*/

//load http module to ceate an http server. 
var http = require('http');
var url  = require('url');

//configure to respond http server with message
http.createServer(function (request, response) {

    //request name parameter
    var url_parts = url.parse(request.url, true);
    var query = url_parts.query;

    //do the mongo
    var mongo = require('mongodb');
    var db = new mongo.Db('nodedb', new mongo.Server('localhost', 27017, {}), {});

    db.open(function() {

        db.collection('Persons', function(err, collection) {

            var cursor = collection.find(query);

            cursor.each(function(err, doc) {

                if(doc) {

                    rdata.push(doc);

                }

            });

        });

    });

    //write what type of response
    response.writeHead(200, {'Content-Type': 'application/json;charset=utf-8'});

    //return data json array
    response.end(JSON.stringify(rdata));

    //clear rdata
    rdata = [];

}).listen(process.env.PORT); 

Answer 1

You have to remember that you are always in an async world with node.js. This caught me out as well coming from a more sync background.

What is happening here is your response is returning before the logic is run. This is because when you call db.open(function() { this goes on the event loop and returns. This is non-blocking so the next line of code that runs is response.writeHead(200, {'Content-Type': 'application/json;charset=utf-8'});. Then the callback for db.open is called, sometime in the future.

In order to correct this. return the response after the cursor.each(function(err, doc) { loop is finished.

Hope this helps.