Indicate progress of the client action.

    This function should be called periodically during client actions that do
    not finish instantly. It will notify the nanny that the action is not stuck
    and avoid the timeout and it will also check if the action has reached its
    cpu limit.

    Raises:
      CPUExceededError: CPU limit exceeded.

def Progress(self):
    """Indicate progress of the client action.

    This function should be called periodically during client actions that do
    not finish instantly. It will notify the nanny that the action is not stuck
    and avoid the timeout and it will also check if the action has reached its
    cpu limit.

    Raises:
      CPUExceededError: CPU limit exceeded.
    """
    now = time.time()
    if now - self.last_progress_time <= 2:
      return

    self.last_progress_time = now

    # Prevent the machine from sleeping while the action is running.
    client_utils.KeepAlive()

    self.grr_worker.Heartbeat()

    user_start = self.cpu_start.user
    system_start = self.cpu_start.system
    cpu_times = self.proc.cpu_times()
    user_end = cpu_times.user
    system_end = cpu_times.system

    used_cpu = user_end - user_start + system_end - system_start

    if used_cpu > self.cpu_limit:
      self.grr_worker.SendClientAlert("Cpu limit exceeded.")
      raise CPUExceededError("Action exceeded cpu limit.")