class ActiveSupport::Cache::FileStore

def increment(name, amount = 1, options = nil)
  file_name = key_file_path(namespaced_key(name, options))
  lock_file(file_name) do
    options = merged_options(options)
    if num = read(name, options)
      num = num.to_i + amount
      write(name, num, options)
      num
    else
      nil
    end
  end
end