Operating State

class ska_control_model.OpStateModel(logger, callback=None, state_machine_factory=None)

This class implements the state model for operational state (“opState”).

The model supports the following states, represented as values of the tango.DevState enum.

  • INIT: the control system is initialising.

  • DISABLE: the control system has been told not to monitor the system under control.

  • UNKNOWN: the control system is monitoring (or at least trying to monitor) the system under control, but is unable to determine its state.

  • OFF: the control system is monitoring the system under control, which is powered off.

  • STANDBY: the control system is monitoring the system under control, which is in low-power standby mode.

  • ON: the control system is monitoring the system under control, which is turned on.

  • FAULT: the control system is monitoring the system under control, which has failed or is in an inconsistent state.

The actions supported are:

  • init_invoked: the control system has started initialising.

  • init_completed: the control system has finished initialising.

  • component_disconnected: the control system his disconnected from the system under control (for example because admin mode was set to OFFLINE). Note, this action indicates a deliberate, control-system-initiated, disconnect; a lost connection would be indicated by a “component_unknown” action.

  • component_unknown: the control system is unable to determine the state of the system under control.

  • component_off: the system under control has been switched off

  • component_standby: the system under control has switched to low-power standby mode

  • component_on: the system under control has been switched on.

  • component_fault: the system under control has experienced a fault.

  • component_no_fault: the system under control has stopped experiencing a fault.

A diagram of the operational state model, as implemented, is shown below.

INIT: The Tango device is initialising. UNKNOWN: The Tango device cannot determine\nthe state of its telescope component. DISABLE: The Tango device is not monitoring\nits telescope component. OFF: The telescope component is turned off STANDBY: The telescope component is standing by ON: The telescope component is turned on FAULT: The telescope component has faulted INIT --down--> DISABLE INIT --down--> UNKNOWN INIT --down--> OFF INIT --down--> STANDBY INIT --down--> ON INIT --down--> FAULT DISABLE -> UNKNOWN DISABLE -> OFF DISABLE -> STANDBY DISABLE -> ON DISABLE -> FAULT UNKNOWN -> DISABLE UNKNOWN -> OFF UNKNOWN -> STANDBY UNKNOWN -> ON UNKNOWN -> FAULT OFF -> DISABLE OFF -> UNKNOWN OFF -> STANDBY OFF -> ON OFF -> FAULT STANDBY -> DISABLE STANDBY -> UNKNOWN STANDBY -> OFF STANDBY -> ON STANDBY -> FAULT ON -> DISABLE ON -> UNKNOWN ON -> OFF ON -> STANDBY ON -> FAULT FAULT -> DISABLE FAULT -> UNKNOWN FAULT -> OFF FAULT -> STANDBY FAULT -> ON

Diagram of the operational state model

The following hierarchical diagram is more explanatory; however note that the implementation does not use a hierarchical state machine.

INIT: The Tango device is initialising. UNKNOWN: The Tango device cannot determine\nthe state of its telescope component. DISABLE: The Tango device is not monitoring\nits telescope component. INIT -right-> DISABLE INIT -right-> MONITORING INIT -right-> UNKNOWN DISABLE -down-> UNKNOWN DISABLE -down-> MONITORING UNKNOWN -up-> DISABLE UNKNOWN -down-> MONITORING MONITORING -up-> DISABLE MONITORING -up-> UNKNOWN state "[monitoring]" as MONITORING { MONITORING: The Tango device is monitoring the telescope component. OFF: The telescope component is turned off STANDBY: The telescope component is standing by ON: The telescope component is turned on FAULT: The telescope component has faulted OFF -right-> STANDBY OFF -right-> FAULT OFF -right-> ON STANDBY -left-> OFF STANDBY -down-> ON STANDBY -down-> FAULT ON -left-> OFF ON -up-> STANDBY ON -down-> FAULT FAULT -left-> OFF FAULT -up-> STANDBY FAULT -up-> ON }

Diagram of the operational state model

__init__(logger, callback=None, state_machine_factory=None)

Initialise the operational state model.

Parameters:

  • logger (Logger) – the logger to be used by this state model.

  • callback (Optional[Callable[[Optional[DevState]], None]]) – A callback to be called when the state machine for op_state reports a change of state

  • state_machine_factory (Optional[Callable[..., LockedMachine]]) – a callable that returns a state machine for this model to use

__weakref__

list of weak references to the object (if defined)

is_action_allowed(action, raise_if_disallowed=False)

Return whether a given action is allowed in the current state.

Parameters:

  • action (str) – an action, as given in the transitions table

  • raise_if_disallowed (bool) – whether to raise an exception if the action is disallowed, or merely return False (optional, defaults to False)

Raises:

StateModelError – if the action is unknown to the state machine

Return type:

bool

Returns:

whether the action is allowed in the current state

property op_state: tango.DevState

Return the op state.

Returns:

the op state of this state model

perform_action(action)

Perform an action on the state model.

Parameters:

action (str) – an action, as given in the transitions table

Return type:

None