Ruby on Rails Global Class Variable not updating when changed

I want to add a slight extension to a class in a ruby gem.

The gem I am using is private_pub : http://ift.tt/YP8RT3 and the class I am overriding is : http://ift.tt/21VnBlr

I am have placed my implementation in a new file in config/initializers called faye_extension.rb. The piece I have added to the code is @@clients and the get_list_of_subscribers class method. The code in faye_extension.rb is as follows:

PrivatePub::FayeExtension
module PrivatePub
  # This class is an extension for the Faye::RackAdapter.
  # It is used inside of PrivatePub.faye_app.
  class FayeExtension
    # Callback to handle incoming Faye messages. This authenticates both
    # subscribe and publish calls.

#####  MY NEW BIT
    @@clients = 0
    def self.get_list_of_subscribers
      @@clients
    end

####


    def incoming(message, callback)
    @@clients = @@clients + 1
      if message["channel"] == "/meta/subscribe"
        authenticate_subscribe(message)
      elsif message["channel"] !~ %r{^/meta/}
        authenticate_publish(message)
      end
      callback.call(message)
    end

  private

    # Ensure the subscription signature is correct and that it has not expired.
    def authenticate_subscribe(message)
      subscription = PrivatePub.subscription(:channel => message["subscription"], :timestamp => message["ext"]["private_pub_timestamp"])
      if message["ext"]["private_pub_signature"] != subscription[:signature]
        message["error"] = "Incorrect signature."
      elsif PrivatePub.signature_expired? message["ext"]["private_pub_timestamp"].to_i
        message["error"] = "Signature has expired."
      end
    end

    # Ensures the secret token is correct before publishing.
    def authenticate_publish(message)
      if PrivatePub.config[:secret_token].nil?
        raise Error, "No secret_token config set, ensure private_pub.yml is loaded properly."
      elsif message["ext"]["private_pub_token"] != PrivatePub.config[:secret_token]
        message["error"] = "Incorrect token."
      else
        message["ext"]["private_pub_token"] = nil
      end
    end
  end
end

When deployed into my application, the incoming() method of the FayeExtension code is called multiple times, however if in a view somewhere I use the following line of code:

<h3><%= PrivatePub::FayeExtension.get_list_of_subscribers.to_s %></h3>

to call my get_list_of_subscribers class method, it always returns 0, despite me calling incoming() 5 times, where I would expect it to output 5. So it seems my @@clients = @@clients +1 code inside of incoming() is not referencing or updating correctly my global variable.

How can I alter the code to achieve this?