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Add breaker.GetState() method to inspect state #45

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Jan 14, 2024
Merged

Add breaker.GetState() method to inspect state #45

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45 changes: 27 additions & 18 deletions breaker/breaker.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -24,7 +27,7 @@ type Breaker struct {
timeout time.Duration

lock sync.Mutex
state uint32
state State
errors, successes int
lastError time.Time
}
Expand All @@ -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
}

Expand All @@ -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
}

Expand All @@ -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 {
Expand All @@ -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
Expand All @@ -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()
Expand All @@ -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() {
Expand All @@ -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))
}
36 changes: 36 additions & 0 deletions breaker/breaker_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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++ {
Expand All @@ -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)
Expand All @@ -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++ {
Expand All @@ -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)
Expand All @@ -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)
Expand All @@ -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)
}
Expand Down