node.js application suddenly loads CPU at 100% and hangs

Question

I have simple application on node.js running on linux virtual machine. It listens for tcp messages and sending them to the clients using socket.io library. And after some time of low CPU usage it suddenly starts to load CPU higher and higher until application hangs up. The script is simple and I can not understand what's wrong with it.

var net = require('net');
var io = require('socket.io').listen(socketPort);

net.createServer(function (socket) {
    socket.setEncoding("utf8");
    socket.on('data', function (dataStr) {
        console.log("TCP dataStr " + dataStr);
        var data = JSON.parse(dataStr);
        io.sockets.in(data.room).emit('publish', data);
    });
}).listen(tcpPort);

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

    socket.on('subscribe', function (room) {
        console.log('subscribe room ' + room);
        if (Array.isArray(room)) {
            var i;
            for (i = 0; i < room.length; i++) {
                console.log('subscribe join room ' + room[i]);
                socket.join(room[i]);
            }
        } else if (typeof room === 'string') {
            console.log('subscribe join room ' + room);
            socket.join(room);
        }
    });

    socket.on('unsubscribe', function (room) {
        console.log('unsubscribe room ' + room);

        if (Array.isArray(room)) {
            var i;
            for (i = 0; i < room.length; i++) {
                console.log('unsubscribe leave room ' + room[i]);
                socket.leave(room[i]);
            }
        } else if (typeof room === 'string') {
            console.log('unsubscribe leave room ' + room);
            socket.leave(room);
        }

    });

});

Also with cluster module I tried to run multiple workers that communicate with clients. And every worker after some time hangs own CPU core at 100% with time difference in about a minute.

UPD: Client code (run in browser):

    socketObj = new function() {
        var that = this;
        that.socket;

        that.init = function(nodeServerUrl, rooms, onPublishFunc) {
            that.socket = io.connect(nodeServerUrl);
            that.socket.emit('subscribe', rooms);

            that.socket.on('publish', function(data) {
                        onPublishFunc(data);
            });
        };
        that.subscribe = function(room) {
            that.socket.emit('subscribe', room);
        };
        that.unsubscribe = function(room) {
            that.socket.emit('unsubscribe', room);
        };
    }

    ...

    try {
        socketObj.init('application url', ["room1", "room2"], nodeJsCallback);
    } catch(err) {
    }

    ...

    nodeJsCallback = function(jsonData) {
        //Only updates data on UI, no subscribing, unsubscribing, emitting etc.
        ...
    }

UPD2: I tried to reproduce the problem with synthetic tests on production machine and on my local Windows machine. I have done some stress testing:

1. Multiple client socket connections
2. Multiple static data downloads (socket.io script for browser)
3. Increased frequence of tcp updates.

After few hours of testing I failed to reproduce. But when it is running on production with real users, it is hanging up earlier or later.

I'm starting to think this is either environment or specific message problem. Probably next things I'll try are:

1. Update Node.js to current version
2. Try to log all data transfer and replay it later hoping hanging will reproduce

Answer 1

Changed Nodejs from version v0.10.4(Stable) to v0.11.2(Unstable). All woking good so far, consuming 1-2% CPU. Now we are testing on v0.10.8(Stable).

UPD On v0.10.8 application is stable too.

Even though the problem dissapeared on v0.10.4(Stable), it is still very strange and discouraging.