Socket.IO Maximum call stack size exceeded - node.js

Question

I've written a small Socket.IO server, which works fine, I can connect to it, I can send/receive messages, so everything is working ok. Just the relevant part of the code is presented here:
var RedisStore = require('socket.io/lib/stores/redis');
const pub = redis.createClient('127.0.0.1', 6379);
const sub = redis.createClient('127.0.0.1', 6379);
const store = redis.createClient('127.0.0.1', 6379);
io.configure(function() {
io.set('store', new RedisStore({
redisPub : pub,
redisSub : sub,
redisClient : store
}));
});
io.sockets.on('connection', function(socket) {
socket.on('message', function(msg) {
pub.publish("lobby", msg);
});
/*
* Subscribe to the lobby and receive messages.
*/
var sub = redis.createClient('127.0.0.1', 6379);
sub.subscribe("lobby");
sub.on('message', function(channel, msg) {
socket.send(msg);
});
});
I've also written a script presented below that connects to the server and spawns connections in the setInterval function, which spawns a new connection each 10milisecons, so it's spawning quite a lot of connections.
#!/usr/bin/env node
var io = require('socket.io-client');
var reconn = {'force new connection': true};
var sockets = [];
var num = 1000;
function startSocket(i) {
sockets[i] = io.connect("http://127.0.0.1:8080", reconn);
sockets[i].on('connect', function() {
console.log("Socket["+i+"] connected.");
});
sockets[i].on('message', function(msg) {
console.log("Socket["+i+"] Message received: "+msg);
});
}
/*
* Start number of sockets.
*/
for(var i=0; i<num; i++) {
startSocket(i);
}
/*
* Send messages forever.
*/
setInterval(function() {
for(var i=0; i<num; i++) {
sockets[i].send("Hello from socket "+i+".");
}
}, 10);
This script is a benchmark tool spawning 1000 connections to the server, but when running for several minutes, the server dies with the following error message:
node.js:0 // Copyright Joyent, Inc. and other Node contributors. ^
RangeError: Maximum call stack size exceeded
I know that there's not enough stack space available so the exception occurs and the process is terminated, but even if I enlarge the stack with the --stack-size variable, this doesn't actually solve the problem, because I can always spawn more connections, which will eventually kill the server.
My question is: how can I prevent this. This is an effective DoS scenario, where anybody can hack together this little script and force the node server to terminate, but I would like to prevent this from happening. I would like Node server to never terminate, just process messages slowly.
Any ideas if this can be prevented. I'm not sure that I would like to block IPs, since I would also like mobile phones to login to the system, where many of them use the same IP, so the node server can mistakenly think a DoS is being in place by one mobile network operation and blocks its IP.
Thank you

Answer 1

If you would like your node server to run forever, no matter what, use https://github.com/nodejitsu/forever
As for the Exception - My hunch is that var sub = redis.createClient('127.0.0.1', 6379); may allocate a variable in the stack each time a connection is established.
I would first try to put var subs = [] in the global scope and
subs[socket.id] = redis.createClient('127.0.0.1', 6379);
Or something like socket.sub = redis.createClient('127.0.0.1', 6379); to piggyback the existing, hopefully heap based, socket.io data structures.
If not working, try to isolate the problem by removing the use of Redis...