MongoDB query resets socket connection to Node.js server

Question

Executing a find query to my MongoDB DB seems to reset the connection and make the node server crash.

My server handles socket events like this:

io.sockets.on('connection', function(socket) {

MongoClient.connect(url, function(err, db) {
    if (err)
        console.log('Error');

    console.log('Connection established to', url);

    var collection = db.collection('spedizioni');

    socket.on('adminReq', function() {
        handlers.handleAdmin(collection, socket);
    });
});
});

the handleAdmin function is:

function handleAdmin(collection, socket) {
console.log('Admin event');
collection.find(null, function(err, raw) {
    console.log('Find function');
    console.log(raw);

    if (err){ 
        socket.emit('err');
        console.log('Error function');

    }
    if (raw) {
        socket.emit('adminRes', raw);
        console.log('Response function');

    } else {
        socket.emit('adminNull');
        console.log('Null function');

    }
});
}

I want the query to return all items on the database; as per the MongoDB manual, I do that by executing a find query without a parameter.

I tried omitting null or using {} as first parameter but nothing changes.

Upon pressing the button to generate the adminReq event, the 'Connection to DB' string is printed on console and the firefox console signals a NEW connection to socket was estabilished; my client script connects at document.load once.

Below is the node console output after that; as you can see the query is executed; looking at the 'raw' output it seems failed attempts were made. err is null and there is nothing else to output.

Looking at other answers about the 'maximum call stack' exceeded it seems it is caused by a recursive function usually, but it's not the case here.

http://pastebin.com/0xv1qcHn

Why is this the output and not the query result? Why is the connection reset?

A very similar function is working fine and the syntax for returning the whole DB seems correct, feels I am missing something very obvious...

hereandnow78 hereandnow78 · Accepted Answer · 2015-09-15T21:31:41

not sure if you should can use null, but i think an empty object should work

you need to convert your result into an array

collection.find({}).toArray(function(err, raw) {
  console.log('Find function');
  console.log(raw);

  if (err){ 
    socket.emit('err');
    console.log('Error function');

  }
  if (raw) {
    socket.emit('adminRes', raw);
    console.log('Response function');

  } else {
    socket.emit('adminNull');
    console.log('Null function');

  }
});

MongoDB query resets socket connection to Node.js server

1 Answers