concurrent users.

If I have:

class ApplicationController < ActionController::Base
  before_filter RubyCAS::Filter
  before_filter :fetch_operator
  include SessionsHelper


  def fetch_operator
    @operator ||= session[:cas_user] && Operator.find_by_uid(session[:cas_user])
    log_out if @operator.nil?


@operator is available for all controllers of my application.
But If I run, for example, two instances of my application from
different locations.
In the first instance the user logs in as 'user1', later from another
location, another user logs in as 'user2', then in @operator now I
have 'user2'.
How can I do if my application is used by more than one user?

That shouldn't happen - each request has its own controller instance,
so setting @operator to one value for one request should have no
effect on its value for another request.