CircuitBreakerState Class Reference

#include <CircuitBreakerState.h>

Inheritance diagram for CircuitBreakerState:

Collaboration diagram for CircuitBreakerState:

Public Types
enum class	State { Closed , Open , HalfOpen }
using	Action = std::function< bool()>
Public Types inherited from QGCAbstractState
using	EntryCallback = std::function< void()>
using	ExitCallback = std::function< void()>
using	EventHandler = std::function< bool(QEvent *)>

Signals
void	tripped ()
	Emitted when the circuit trips (too many failures)
void	circuitReset ()
	Emitted when the circuit resets (after successful half-open test)
void	succeeded ()
	Emitted when action succeeds.
void	failed ()
	Emitted when action fails (or circuit is open)
Signals inherited from QGCAbstractState
void	advance ()
void	error ()

Public Member Functions
	CircuitBreakerState (const QString &stateName, QState *parent, Action action, int failureThreshold=5, int resetTimeoutMsecs=30000)
State	circuitState () const
	Get the current circuit state.
int	failureCount () const
	Get the current failure count.
int	failureThreshold () const
	Get the failure threshold.
void	reset ()
	Manually reset the circuit breaker.
bool	isTripped () const
	Check if the circuit is currently tripped (open)
Public Member Functions inherited from QGCState
	QGCState (const QString &stateName, QState *parentState)
template<typename PointerToMemberFunction >
QSignalTransition *	addThisTransition (PointerToMemberFunction signal, QAbstractState *target)
	Simpler version of QState::addTransition which assumes the sender is this.
void	setLocalErrorState (QAbstractState *errorState)
QAbstractState *	localErrorState () const
	Get the per-state error state (nullptr if using global)
void	setProperty (QObject *object, const char *name, const QVariant &value)
void	setEnabled (QObject *object, bool enabled)
	Convenience overload for setting enabled state on widgets/controls.
void	setVisible (QObject *object, bool visible)
	Convenience overload for setting visible state on widgets/controls.
Public Member Functions inherited from QGCAbstractState
	QGCAbstractState (const QString &stateName, QState *parent)
QGCStateMachine *	machine () const
Vehicle *	vehicle () const
QString	stateName () const
class StateContext *	context () const
void	setOnEntry (EntryCallback callback)
	Set a callback to be invoked when the state is entered.
void	setOnExit (ExitCallback callback)
	Set a callback to be invoked when the state is exited.
void	setCallbacks (EntryCallback onEntry, ExitCallback onExit=nullptr)
	Set both entry and exit callbacks.
void	setEventHandler (EventHandler handler)
	Set a custom event handler for this state.

Protected Member Functions
void	onEnter () override
	Override to perform actions on state entry.
Protected Member Functions inherited from QGCAbstractState
virtual void	onLeave ()
	Override to perform actions on state exit.
void	onEntry (QEvent *event) override
void	onExit (QEvent *event) override
bool	event (QEvent *event) override

Detailed Description

A state that implements the circuit breaker pattern.

After a threshold of failures, the circuit "trips" and immediately fails without attempting the action for a reset timeout period. This prevents cascading failures when an external service is down.

States:

• Closed: Normal operation, action is attempted
• Open: Tripped, immediately fails without trying
• Half-Open: After reset timeout, allows one attempt to test recovery

Example usage:

auto* state = new CircuitBreakerState("ExternalAPI", &machine,
    []() { return callExternalApi(); },
    5,      // Failure threshold
    30000   // Reset timeout (ms)
);
 
state->addTransition(state, &CircuitBreakerState::advance, successState);
state->addTransition(state, &CircuitBreakerState::error, errorState);

Definition at line 31 of file CircuitBreakerState.h.

Member Typedef Documentation

Action

using CircuitBreakerState::Action = std::function<bool()>

Definition at line 37 of file CircuitBreakerState.h.

Member Enumeration Documentation

State

enum class CircuitBreakerState::State

strong

Enumerator
Closed	Normal operation.
Open	Tripped, failing fast.
HalfOpen	Testing if service recovered.

Definition at line 39 of file CircuitBreakerState.h.

Constructor & Destructor Documentation

CircuitBreakerState()

CircuitBreakerState::CircuitBreakerState	(	const QString &	stateName,
		QState *	parent,
		Action	action,
		int	failureThreshold = 5,
		int	resetTimeoutMsecs = 30000
	)

Parameters

stateName	Name for logging
parent	Parent state
action	Action to execute (returns true on success)
failureThreshold	Number of failures before tripping
resetTimeoutMsecs	Time before attempting recovery

Definition at line 4 of file CircuitBreakerState.cc.

Member Function Documentation

circuitReset

void CircuitBreakerState::circuitReset ( )

signal

Emitted when the circuit resets (after successful half-open test)

Referenced by reset().

circuitState()

State CircuitBreakerState::circuitState ( ) const

inline

Get the current circuit state.

Definition at line 56 of file CircuitBreakerState.h.

failed

void CircuitBreakerState::failed ( )

signal

Emitted when action fails (or circuit is open)

Referenced by onEnter().

failureCount()

int CircuitBreakerState::failureCount ( ) const

inline

Get the current failure count.

Definition at line 59 of file CircuitBreakerState.h.

failureThreshold()

int CircuitBreakerState::failureThreshold ( ) const

inline

Get the failure threshold.

Definition at line 62 of file CircuitBreakerState.h.

isTripped()

bool CircuitBreakerState::isTripped ( ) const

inline

Check if the circuit is currently tripped (open)

Definition at line 68 of file CircuitBreakerState.h.

References Open.

onEnter()

void CircuitBreakerState::onEnter ( )

overrideprotectedvirtual

Override to perform actions on state entry.

Reimplemented from QGCAbstractState.

Definition at line 22 of file CircuitBreakerState.cc.

References QGCAbstractState::advance(), QGCAbstractState::error(), failed(), HalfOpen, Open, reset(), QGCAbstractState::stateName(), succeeded(), and tripped().

reset()

void CircuitBreakerState::reset

(

)

Manually reset the circuit breaker.

Definition at line 14 of file CircuitBreakerState.cc.

References circuitReset(), Closed, and QGCAbstractState::stateName().

Referenced by onEnter().

succeeded

void CircuitBreakerState::succeeded ( )

signal

Emitted when action succeeds.

Referenced by onEnter().

tripped

void CircuitBreakerState::tripped ( )

signal

Emitted when the circuit trips (too many failures)

Referenced by onEnter().

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The documentation for this class was generated from the following files:

• src/Utilities/StateMachine/States/CircuitBreakerState.h
• src/Utilities/StateMachine/States/CircuitBreakerState.cc