ironic.common.fsm module

class ironic.common.fsm.FSM[source]

Bases: automaton.machines.FiniteMachine

An ironic state-machine class with some ironic specific additions.

add_state(state, on_enter=None, on_exit=None, target=None, terminal=None, stable=False)[source]

Adds a given state to the state machine.

Parameters
  • stable – Use this to specify that this state is a stable/passive state. A state must have been previously defined as ‘stable’ before it can be used as a ‘target’

  • target – The target state for ‘state’ to go to. Before a state can be used as a target it must have been previously added and specified as ‘stable’

Further arguments are interpreted as for parent method add_state.

add_transition(start, end, event, replace=False)

Adds an allowed transition from start -> end for the given event.

Parameters
  • start – starting state

  • end – ending state

  • event – event that causes start state to transition to end state

  • replace – replace existing event instead of raising a Duplicate exception when the transition already exists.

initialize(start_state=None, target_state=None)[source]

Initialize the FSM.

Parameters
  • start_state – the FSM is initialized to start from this state

  • target_state – if specified, the FSM is initialized to this target state. Otherwise use the default target state

is_stable(state)[source]

Is the state stable?

Parameters

state – the state of interest

Raises

InvalidState if the state is invalid

Returns

True if it is a stable state; False otherwise

process_event(event, target_state=None)[source]

process the event.

Parameters
  • event – the event to be processed

  • target_state – if specified, the ‘final’ target state for the event. Otherwise, use the default target state

property target_state