socket.io / engine.io load balancing with stickyness using nginx hash

client.js

// Same random hash will be used during the whole session
var hash = Math.random().toString(36).slice(2, 10)
// Get absolute uri
var uri = document.createElement('a')
uri.href = '/engine.io/?hash=' + hash
var socket = eio(uri.href)

nginx.conf

http {
  upstream eio {
    hash $arg_hash consistent;
    server localhost:3001;
    server localhost:3002;
  }

  server {
    listen 3000;

    location /engine.io {
      proxy_pass              http://eio;
      proxy_http_version      1.1;
      proxy_next_upstream     error timeout invalid_header;
      proxy_connect_timeout   2;

      proxy_set_header        Host $host;
      proxy_set_header        Upgrade $http_upgrade;
      proxy_set_header        Connection "upgrade";
    }
  }
}