heronpy/api/state/stateful_component.py

#!/usr/bin/env python3
# -*- encoding: utf-8 -*-

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'''stateful_component.py'''
from abc import abstractmethod

class StatefulComponent(object):
  """Defines a component that saves its internal state using the State interface
  When running under effectively once semantics, the state is periodically checkpointed
  and is replayed when errors occur to a globally consistent checkpoint.
  """
  @abstractmethod
  def init_state(self, state):
    """Initializes the state of the function or operator to that of a previous checkpoint.
    This method is invoked when a component is executed as part of a recovery run. In case
    there was no prior state associated with the component, the state will be empty.
    Stateful Spouts/Bolts are expected to hold on to the state variable to save their
    internal state
    Note that init_state() is called before initialize()
    :param state: the previously saved state of the component.
    """
    pass

  @abstractmethod
  def pre_save(self):
    """This is a hook for the component to perform some actions just before the
    framework saves its state.
    """
    pass