Merge pull request #45 from eapache/breaker/get-state

Add breaker.GetState() method to inspect state

Author: eapache

breaker/breaker.go

@@ -12,10 +12,13 @@ import (
 // because the breaker is currently open.
 var ErrBreakerOpen = errors.New("circuit breaker is open")
 
+// State is a type representing the possible states of a circuit breaker.
+type State uint32
+
 const (
-	closed uint32 = iota
-	open
-	halfOpen
+	Closed State = iota
+	Open
+	HalfOpen
 )
 
 // Breaker implements the circuit-breaker resiliency pattern
@@ -24,7 +27,7 @@ type Breaker struct {
 	timeout                          time.Duration
 
 	lock              sync.Mutex
-	state             uint32
+	state             State
 	errors, successes int
 	lastError         time.Time
 }
@@ -46,9 +49,9 @@ func New(errorThreshold, successThreshold int, timeout time.Duration) *Breaker {
 // already open, or it will run the given function and pass along its return
 // value. It is safe to call Run concurrently on the same Breaker.
 func (b *Breaker) Run(work func() error) error {
-	state := atomic.LoadUint32(&b.state)
+	state := b.GetState()
 
-	if state == open {
+	if state == Open {
 		return ErrBreakerOpen
 	}
 
@@ -61,9 +64,9 @@ func (b *Breaker) Run(work func() error) error {
 // the return value of the function. It is safe to call Go concurrently on the
 // same Breaker.
 func (b *Breaker) Go(work func() error) error {
-	state := atomic.LoadUint32(&b.state)
+	state := b.GetState()
 
-	if state == open {
+	if state == Open {
 		return ErrBreakerOpen
 	}
 
@@ -75,7 +78,13 @@ func (b *Breaker) Go(work func() error) error {
 	return nil
 }
 
-func (b *Breaker) doWork(state uint32, work func() error) error {
+// GetState returns the current State of the circuit-breaker at the moment
+// that it is called.
+func (b *Breaker) GetState() State {
+	return (State)(atomic.LoadUint32((*uint32)(&b.state)))
+}
+
+func (b *Breaker) doWork(state State, work func() error) error {
 	var panicValue interface{}
 
 	result := func() error {
@@ -85,7 +94,7 @@ func (b *Breaker) doWork(state uint32, work func() error) error {
 		return work()
 	}()
 
-	if result == nil && panicValue == nil && state == closed {
+	if result == nil && panicValue == nil && state == Closed {
 		// short-circuit the normal, success path without contending
 		// on the lock
 		return nil
@@ -108,7 +117,7 @@ func (b *Breaker) processResult(result error, panicValue interface{}) {
 	defer b.lock.Unlock()
 
 	if result == nil && panicValue == nil {
-		if b.state == halfOpen {
+		if b.state == HalfOpen {
 			b.successes++
 			if b.successes == b.successThreshold {
 				b.closeBreaker()
@@ -123,26 +132,26 @@ func (b *Breaker) processResult(result error, panicValue interface{}) {
 		}
 
 		switch b.state {
-		case closed:
+		case Closed:
 			b.errors++
 			if b.errors == b.errorThreshold {
 				b.openBreaker()
 			} else {
 				b.lastError = time.Now()
 			}
-		case halfOpen:
+		case HalfOpen:
 			b.openBreaker()
 		}
 	}
 }
 
 func (b *Breaker) openBreaker() {
-	b.changeState(open)
+	b.changeState(Open)
 	go b.timer()
 }
 
 func (b *Breaker) closeBreaker() {
-	b.changeState(closed)
+	b.changeState(Closed)
 }
 
 func (b *Breaker) timer() {
@@ -151,11 +160,11 @@ func (b *Breaker) timer() {
 	b.lock.Lock()
 	defer b.lock.Unlock()
 
-	b.changeState(halfOpen)
+	b.changeState(HalfOpen)
 }
 
-func (b *Breaker) changeState(newState uint32) {
+func (b *Breaker) changeState(newState State) {
 	b.errors = 0
 	b.successes = 0
-	atomic.StoreUint32(&b.state, newState)
+	atomic.StoreUint32((*uint32)(&b.state), (uint32)(newState))
 }

breaker/breaker_test.go

@@ -22,24 +22,36 @@ func returnsSuccess() error {
 
 func TestBreakerErrorExpiry(t *testing.T) {
 	breaker := New(2, 1, 10*time.Millisecond)
+	if breaker.GetState() != Closed {
+		t.Error("incorrect state")
+	}
 
 	for i := 0; i < 3; i++ {
 		if err := breaker.Run(returnsError); err != errSomeError {
 			t.Error(err)
 		}
 		time.Sleep(10 * time.Millisecond)
 	}
+	if breaker.GetState() != Closed {
+		t.Error("incorrect state")
+	}
 
 	for i := 0; i < 3; i++ {
 		if err := breaker.Go(returnsError); err != nil {
 			t.Error(err)
 		}
 		time.Sleep(10 * time.Millisecond)
 	}
+	if breaker.GetState() != Closed {
+		t.Error("incorrect state")
+	}
 }
 
 func TestBreakerPanicsCountAsErrors(t *testing.T) {
 	breaker := New(3, 2, 1*time.Second)
+	if breaker.GetState() != Closed {
+		t.Error("incorrect state")
+	}
 
 	// three errors opens the breaker
 	for i := 0; i < 3; i++ {
@@ -58,6 +70,9 @@ func TestBreakerPanicsCountAsErrors(t *testing.T) {
 	}
 
 	// breaker is open
+	if breaker.GetState() != Open {
+		t.Error("incorrect state")
+	}
 	for i := 0; i < 5; i++ {
 		if err := breaker.Run(returnsError); err != ErrBreakerOpen {
 			t.Error(err)
@@ -67,6 +82,9 @@ func TestBreakerPanicsCountAsErrors(t *testing.T) {
 
 func TestBreakerStateTransitions(t *testing.T) {
 	breaker := New(3, 2, 10*time.Millisecond)
+	if breaker.GetState() != Closed {
+		t.Error("incorrect state")
+	}
 
 	// three errors opens the breaker
 	for i := 0; i < 3; i++ {
@@ -76,6 +94,9 @@ func TestBreakerStateTransitions(t *testing.T) {
 	}
 
 	// breaker is open
+	if breaker.GetState() != Open {
+		t.Error("incorrect state")
+	}
 	for i := 0; i < 5; i++ {
 		if err := breaker.Run(returnsError); err != ErrBreakerOpen {
 			t.Error(err)
@@ -84,6 +105,9 @@ func TestBreakerStateTransitions(t *testing.T) {
 
 	// wait for it to half-close
 	time.Sleep(20 * time.Millisecond)
+	if breaker.GetState() != HalfOpen {
+		t.Error("incorrect state")
+	}
 	// one success works, but is not enough to fully close
 	if err := breaker.Run(returnsSuccess); err != nil {
 		t.Error(err)
@@ -93,23 +117,35 @@ func TestBreakerStateTransitions(t *testing.T) {
 		t.Error(err)
 	}
 	// breaker is open
+	if breaker.GetState() != Open {
+		t.Error("incorrect state")
+	}
 	if err := breaker.Run(returnsError); err != ErrBreakerOpen {
 		t.Error(err)
 	}
 
 	// wait for it to half-close
 	time.Sleep(20 * time.Millisecond)
+	if breaker.GetState() != HalfOpen {
+		t.Error("incorrect state")
+	}
 	// two successes is enough to close it for good
 	for i := 0; i < 2; i++ {
 		if err := breaker.Run(returnsSuccess); err != nil {
 			t.Error(err)
 		}
 	}
+	if breaker.GetState() != Closed {
+		t.Error("incorrect state")
+	}
 	// error works
 	if err := breaker.Run(returnsError); err != errSomeError {
 		t.Error(err)
 	}
 	// breaker is still closed
+	if breaker.GetState() != Closed {
+		t.Error("incorrect state")
+	}
 	if err := breaker.Run(returnsSuccess); err != nil {
 		t.Error(err)
 	}