Question

I’m a big Node.js and Mongo newbie, so please be gentle.

So here’s my Node.js app:

var mongo = require('mongodb');
var Server = mongo.Server;
var Db = mongo.Db;

var server = new Server('hostname.mongolab.com', 666, {auto_reconnect : true}, {w:0, native_parser: false});
var db = new Db('dbName', server, {safe:true});

db.open(function(err, client) {
  if(err) { return console.dir(err); }
  client.authenticate('mongolabUser', 'mongolabUserPassword', function(authErr, success) {
    if(authErr) { return console.dir(authErr); }
    var stream  = client.collection('myCollection').find({}).stream();
    stream.on('data', function(item) {console.log("Do something with item"); });
    stream.on('end', function() {console.log("Empty!");});
  });
  db.close();
});

Through prodigious use of debugger statements, I’ve come to the conclusion that the client.authenticate doesn’t seem to be run. It looks like it’s about to execute that line, but then just leapfrogs over it and goes straight to db.close().

But that’s just the first of my problems. At some point prior, I was able to connect in to the database and authenticate, but my user was no retrieving anything in the find({}) command. I tried all sorts of ways, and streams are my latest attempt before deciding to give up on it for now.

Mongolab seems to be on v2.0.7, my mongo installation is v2.2.1. When I use the command line tool to log in as mongolabUser and execute a command like db.myCollection.find(), I get everything in my collection, so it can’t be an issue with permissions.

Any advice/suggestions?

Answer 1

client.authenticate() is asynchronous, so the line that calls it starts the authentication, but doesn’t wait for the server to respond before moving on to executing the next line, db.close(). So by the time the server responds the connection has been closed by the client.

Does moving the db.close() inside the event handler for stream.end help?

var mongo = require('mongodb');
var Server = mongo.Server;
var Db = mongo.Db;

var server = new Server('hostname.mongolab.com', 666, {auto_reconnect : true}, {w:0, native_parser: false});
var db = new Db('dbName', server, {safe:true});

db.open(function(err, client) {
  if(err) { return console.dir(err); }
  client.authenticate('mongolabUser', 'mongolabUserPassword', function(authErr, success) {
    if(authErr) { return console.dir(authErr); }
    var stream  = client.collection('myCollection').find({}).stream();
    stream.on('data', function(item) {console.log("Do something with item"); });
    stream.on('end', function() {
      console.log("Empty!");
      db.close();
    });
  });
});