Node.js net module remoteAddress is undefined - node.js

Question

I have a Node app running on AWS Elastic Beanstalk (so Node running behind Nginx). I am running socket IO with redis as the memory store and have Node running clustered using the cluster module. Generally everything works great but every now and then I get a user trying to connect that throws an undefined error on the connection.remoteAddress. My code looks like this for the connections:
if (cluster.isMaster) {
/*
------------------------------------------------------------------------------------
This stores our workers. We need to keep them to be able to reference
them based on source IP address. It's also useful for auto-restart
We also setup a message listener to every worker in order to blast AND FILTER
socket io updates to all nodes.
------------------------------------------------------------------------------------
*/
var workers = [];
var messageRelay = function(msg) {
for(var i = 0; i < workers.length; i++) {
workers[i].send(msg);
}
};
var spawn = function(i) {
workers[i] = cluster.fork();
console.log("Hello from worker %s",workers[i].process.pid);
workers[i].on('message', messageRelay);
/*
----------------------------------------
Restart worker if it gets destroyed
----------------------------------------
*/
workers[i].on('disconnect', function(worker) {
console.log('Worker disconnected');
});
workers[i].on('exit', function(worker, code, signal) {
console.log('respawning worker', i);
spawn(i);
});
};
for (var i = 0; i < cpuCount; i++) {
spawn(i);
}
/*
--------------------------------------------------------------------------------------------
Helper function for getting a worker index based on IP address (supports IPv4 AND IPv6)
This is a hot path so it should be really fast. The way it works
is by converting the IP address to a number by removing the dots (for IPv4) and removing
the :: for IPv6, then compressing it to the number of slots we have.
Compared against "real" hashing (from the sticky-session code) and
"real" IP number conversion, this function is on par in terms of
worker index distribution only much faster.
--------------------------------------------------------------------------------------------
*/
var workerIndex = function (ip, len) {
var _ip = ip.split(/['.'|':']/),
arr = [];
for (el in _ip) {
if (_ip[el] == '') {
arr.push(0);
}
else {
arr.push(parseInt(_ip[el], 16));
}
}
return Number(arr.join('')) % len;
}
/*
------------------------------------------------------------------------------------
Create the outside facing server listening on our port.
------------------------------------------------------------------------------------
*/
var server = net.createServer({ pauseOnConnect: true }, function(connection) {
/*
------------------------------------------------------------------------------------
We received a connection and need to pass it to the appropriate
worker. Get the worker for this connection's source IP and pass
it the connection.
------------------------------------------------------------------------------------
*/
if(connection.remoteAddress === undefined) {
console.log("BLEH: %o ", connection.remoteAddress);
return;
}
else {
var worker = workers[workerIndex(connection.remoteAddress, cpuCount)];
worker.send('sticky-session:connection', connection);
}
}).listen(port, function() {
console.log("Spun up worker %s", process.pid);
console.log('Server listening on *:' + port);
});
}
else {
var sio = require('socket.io');
var redis = require('socket.io-redis');
var ioEvents = require(__base + 'lib/ioEvents');
var app = new express();
/*
------------------------------------------------------------------------------------
Note we don't use a port here because the master listens on it for us.
------------------------------------------------------------------------------------
*/
var server = app.listen(0, 'localhost'),
io = sio(server);
/*
----------------------------------------------------------------------------------------------
Using Redis as the store instead of memory. This allows us to blast socket updates
to all processes (unfiltered). For example, we can do io.sockets.emit("message")
and it will be distributed to all node processes.
We cannot filter these messages to specific socket connections or specific configurations
(e.g. updateSquares(socket)), in order to do that we must blast an update to all workers
and let each process filter the request individually.
----------------------------------------------------------------------------------------------
*/
io.adapter(redis({host:'localhost', port: portRedis}));
/*
------------------------------------------------------------------------------------
Setup the socket listeners
------------------------------------------------------------------------------------
*/
ioEvents.incoming(io);
/*
------------------------------------------------------------------------------------
Listen to master for worker process updates
------------------------------------------------------------------------------------
*/
process.on('message', function(message, connection) {
/*
------------------------------------------------------------------------------------
Listen for special updates to all nodes
------------------------------------------------------------------------------------
*/
if(message.squareUpdate) {
console.log("worker %s received message %o", process.pid, message.squareUpdate);
ioEvents.squaresForceUpdate(message.squareUpdate);
}
/*
------------------------------------------------------------------------------------
If it's not a special message, then check to make sure it's just a sticky-session
Otherwise, just bail, no need to do anything else
------------------------------------------------------------------------------------
*/
if (message !== 'sticky-session:connection') {
return;
}
/*
------------------------------------------------------------------------------------
| Emulate a connection event on the server by emitting the
| event with the connection the master sent us.
------------------------------------------------------------------------------------
*/
server.emit('connection', connection);
connection.resume();
});
So the problem lies in the section above with the "BLEH" log. For some reason, remoteAddress is undefined...but only SOMETIMES. Most of the connections look just fine, but randomly I'll get a user trying to connect that throws that error. I'd like to understand what is going on here. I've read that I cannot do IP stuff when there is a proxy involved (something between Node and the User)...but 98% of the time, the connections to workers are fine and everything works as expected. Any help here is really appreciated.