nginx 1.3.14 + nginx-sticky-module = ws/xhr polling + round robin + sticky sessions

nginx.conf

http {
    upstream client_handler {
        sticky; # !important
        server 127.0.0.1:8000;
        server 127.0.0.1:8001;
        server 127.0.0.1:8002;
        server 127.0.0.1:8003;
    }

    map $http_upgrade $connection_upgrade {
            default upgrade;
            ''      close;
    }

    server {
        listen 80 default_server;
        #server_name alena3;
        
        location / {
            root /home/www/public;
            index index.html index.htm;
        } 

        location /engine.io/ {
                proxy_pass http://client_handler;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection $connection_upgrade;
        }       
    }
}