如果您使用的是 active_record_store 用于会话，您可以尝试类似以下操作：

If you are using the active_record_store for your sessions, you can try something like this:

sessions = CGI::Session::ActiveRecordStore::Session.find(:all, :conditions => ["updated_at >= ?", 15.minutes.ago], :order => "created_at ASC")
sessions.each do |session|
  if session.data[:user]
    online_users << User.find(session.data[:user])
  end
end