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/*
* Copyright (C) 2009-2020 Lightbend Inc.
*/
package akka.pattern
import java.util.Optional
import java.util.concurrent.{ Callable, CompletionStage, CopyOnWriteArrayList }
import java.util.concurrent.atomic.{ AtomicBoolean, AtomicInteger, AtomicLong }
import java.util.function.BiFunction
import java.util.function.Consumer
import scala.compat.java8.FutureConverters
import scala.concurrent.{ Await, ExecutionContext, Future, Promise }
import scala.concurrent.TimeoutException
import scala.concurrent.duration._
import scala.util.{ Failure, Success, Try }
import scala.util.control.NoStackTrace
import scala.util.control.NonFatal
import com.github.ghik.silencer.silent
import akka.AkkaException
import akka.actor.Scheduler
import akka.dispatch.ExecutionContexts.parasitic
import akka.util.JavaDurationConverters._
import akka.util.Unsafe
/**
* Companion object providing factory methods for Circuit Breaker which runs callbacks in caller's thread
*/
object CircuitBreaker {
/**
* Create a new CircuitBreaker.
*
* Callbacks run in caller's thread when using withSyncCircuitBreaker, and in same ExecutionContext as the passed
* in Future when using withCircuitBreaker. To use another ExecutionContext for the callbacks you can specify the
* executor in the constructor.
*
* @param scheduler Reference to Akka scheduler
* @param maxFailures Maximum number of failures before opening the circuit
* @param callTimeout [[scala.concurrent.duration.FiniteDuration]] of time after which to consider a call a failure
* @param resetTimeout [[scala.concurrent.duration.FiniteDuration]] of time after which to attempt to close the circuit
*/
def apply(
scheduler: Scheduler,
maxFailures: Int,
callTimeout: FiniteDuration,
resetTimeout: FiniteDuration): CircuitBreaker =
new CircuitBreaker(scheduler, maxFailures, callTimeout, resetTimeout)(parasitic)
/**
* Java API: Create a new CircuitBreaker.
*
* Callbacks run in caller's thread when using withSyncCircuitBreaker, and in same ExecutionContext as the passed
* in Future when using withCircuitBreaker. To use another ExecutionContext for the callbacks you can specify the
* executor in the constructor.
*
* @param scheduler Reference to Akka scheduler
* @param maxFailures Maximum number of failures before opening the circuit
* @param callTimeout [[scala.concurrent.duration.FiniteDuration]] of time after which to consider a call a failure
* @param resetTimeout [[scala.concurrent.duration.FiniteDuration]] of time after which to attempt to close the circuit
*/
@deprecated("Use the overloaded one which accepts java.time.Duration instead.", since = "2.5.12")
def create(
scheduler: Scheduler,
maxFailures: Int,
callTimeout: FiniteDuration,
resetTimeout: FiniteDuration): CircuitBreaker =
apply(scheduler, maxFailures, callTimeout, resetTimeout)
/**
* Java API: Create a new CircuitBreaker.
*
* Callbacks run in caller's thread when using withSyncCircuitBreaker, and in same ExecutionContext as the passed
* in Future when using withCircuitBreaker. To use another ExecutionContext for the callbacks you can specify the
* executor in the constructor.
*
* @param scheduler Reference to Akka scheduler
* @param maxFailures Maximum number of failures before opening the circuit
* @param callTimeout [[java.time.Duration]] of time after which to consider a call a failure
* @param resetTimeout [[java.time.Duration]] of time after which to attempt to close the circuit
*/
def create(
scheduler: Scheduler,
maxFailures: Int,
callTimeout: java.time.Duration,
resetTimeout: java.time.Duration): CircuitBreaker =
apply(scheduler, maxFailures, callTimeout.asScala, resetTimeout.asScala)
private val exceptionAsFailure: Try[_] => Boolean = {
case _: Success[_] => false
case _ => true
}
private def exceptionAsFailureJava[T]: BiFunction[Optional[T], Optional[Throwable], java.lang.Boolean] =
new BiFunction[Optional[T], Optional[Throwable], java.lang.Boolean] {
override def apply(t: Optional[T], err: Optional[Throwable]) = {
if (err.isPresent)
true
else
false
}
}
protected def convertJavaFailureFnToScala[T](
javaFn: BiFunction[Optional[T], Optional[Throwable], java.lang.Boolean]): Try[T] => Boolean = {
val failureFnInScala: Try[T] => Boolean = {
case Success(t) => javaFn(Optional.of(t), Optional.empty())
case Failure(err) => javaFn(Optional.empty(), Optional.of(err))
}
failureFnInScala
}
}
/**
* Provides circuit breaker functionality for stability when working with "dangerous" operations, e.g. calls to
* remote systems.
*
* Transitions through three states:
* - In *Closed* state, calls pass through until the `maxFailures` count is reached. This causes the circuit breaker
* to open. Both exceptions and calls exceeding `callTimeout` are considered failures.
* - In *Open* state, calls fail-fast with an exception. After `resetTimeout`, circuit breaker transitions to
* half-open state.
* - In *Half-Open* state, the first call will be allowed through, if it succeeds the circuit breaker will reset to
* closed state. If it fails, the circuit breaker will re-open to open state. All calls beyond the first that
* execute while the first is running will fail-fast with an exception.
*
* @param scheduler Reference to Akka scheduler
* @param maxFailures Maximum number of failures before opening the circuit
* @param callTimeout [[scala.concurrent.duration.FiniteDuration]] of time after which to consider a call a failure
* @param resetTimeout [[scala.concurrent.duration.FiniteDuration]] of time after which to attempt to close the circuit
* @param executor [[scala.concurrent.ExecutionContext]] used for execution of state transition listeners
*/
class CircuitBreaker(
scheduler: Scheduler,
maxFailures: Int,
callTimeout: FiniteDuration,
val resetTimeout: FiniteDuration,
maxResetTimeout: FiniteDuration,
exponentialBackoffFactor: Double)(implicit executor: ExecutionContext)
extends AbstractCircuitBreaker {
require(exponentialBackoffFactor >= 1.0, "factor must be >= 1.0")
@deprecated("Use the overloaded one which accepts java.time.Duration instead.", since = "2.5.12")
def this(
executor: ExecutionContext,
scheduler: Scheduler,
maxFailures: Int,
callTimeout: FiniteDuration,
resetTimeout: FiniteDuration) = {
this(scheduler, maxFailures, callTimeout, resetTimeout, 36500.days, 1.0)(executor)
}
def this(
executor: ExecutionContext,
scheduler: Scheduler,
maxFailures: Int,
callTimeout: java.time.Duration,
resetTimeout: java.time.Duration) = {
this(scheduler, maxFailures, callTimeout.asScala, resetTimeout.asScala, 36500.days, 1.0)(executor)
}
// add the old constructor to make it binary compatible
def this(scheduler: Scheduler, maxFailures: Int, callTimeout: FiniteDuration, resetTimeout: FiniteDuration)(
implicit
executor: ExecutionContext) = {
this(scheduler, maxFailures, callTimeout, resetTimeout, 36500.days, 1.0)(executor)
}
/**
* The `resetTimeout` will be increased exponentially for each failed attempt to close the circuit.
* The default exponential backoff factor is 2.
*
* @param maxResetTimeout the upper bound of resetTimeout
*/
def withExponentialBackoff(maxResetTimeout: FiniteDuration): CircuitBreaker = {
new CircuitBreaker(scheduler, maxFailures, callTimeout, resetTimeout, maxResetTimeout, 2.0)(executor)
}
/**
* The `resetTimeout` will be increased exponentially for each failed attempt to close the circuit.
* The default exponential backoff factor is 2.
*
* @param maxResetTimeout the upper bound of resetTimeout
*/
def withExponentialBackoff(maxResetTimeout: java.time.Duration): CircuitBreaker = {
withExponentialBackoff(maxResetTimeout.asScala)
}
/**
* Holds reference to current state of CircuitBreaker - *access only via helper methods*
*/
@volatile
@silent("never used")
private[this] var _currentStateDoNotCallMeDirectly: State = Closed
/**
* Holds reference to current resetTimeout of CircuitBreaker - *access only via helper methods*
*/
@volatile
@silent("never used")
private[this] var _currentResetTimeoutDoNotCallMeDirectly: FiniteDuration = resetTimeout
/**
* Helper method for access to underlying state via Unsafe
*
* @param oldState Previous state on transition
* @param newState Next state on transition
* @return Whether the previous state matched correctly
*/
@inline
private[this] def swapState(oldState: State, newState: State): Boolean =
Unsafe.instance.compareAndSwapObject(this, AbstractCircuitBreaker.stateOffset, oldState, newState)
/**
* Helper method for accessing underlying state via Unsafe
*
* @return Reference to current state
*/
@inline
private[this] def currentState: State =
Unsafe.instance.getObjectVolatile(this, AbstractCircuitBreaker.stateOffset).asInstanceOf[State]
/**
* Helper method for updating the underlying resetTimeout via Unsafe
*/
@inline
private[this] def swapResetTimeout(oldResetTimeout: FiniteDuration, newResetTimeout: FiniteDuration): Boolean =
Unsafe.instance.compareAndSwapObject(
this,
AbstractCircuitBreaker.resetTimeoutOffset,
oldResetTimeout,
newResetTimeout)
/**
* Helper method for accessing to the underlying resetTimeout via Unsafe
*/
@inline
private[this] def currentResetTimeout: FiniteDuration =
Unsafe.instance.getObjectVolatile(this, AbstractCircuitBreaker.resetTimeoutOffset).asInstanceOf[FiniteDuration]
/**
* Wraps invocations of asynchronous calls that need to be protected.
*
* @param body Call needing protected
* @param defineFailureFn function that define what should be consider failure and thus increase failure count
* @return [[scala.concurrent.Future]] containing the call result or a
* `scala.concurrent.TimeoutException` if the call timed out
*/
def withCircuitBreaker[T](body: => Future[T], defineFailureFn: Try[T] => Boolean): Future[T] =
currentState.invoke(body, defineFailureFn)
/**
* Wraps invocations of asynchronous calls that need to be protected.
*
* @param body Call needing protected
* @return [[scala.concurrent.Future]] containing the call result or a
* `scala.concurrent.TimeoutException` if the call timed out
*
*/
def withCircuitBreaker[T](body: => Future[T]): Future[T] =
currentState.invoke(body, CircuitBreaker.exceptionAsFailure)
/**
* Java API for [[#withCircuitBreaker]].
*
* @param body Call needing protected
* @return [[scala.concurrent.Future]] containing the call result or a
* `scala.concurrent.TimeoutException` if the call timed out
*/
def callWithCircuitBreaker[T](body: Callable[Future[T]]): Future[T] =
callWithCircuitBreaker(body, CircuitBreaker.exceptionAsFailureJava[T])
/**
* Java API for [[#withCircuitBreaker]].
*
* @param body Call needing protected
* @param defineFailureFn function that define what should be consider failure and thus increase failure count
* @return [[scala.concurrent.Future]] containing the call result or a
* `scala.concurrent.TimeoutException` if the call timed out
*/
def callWithCircuitBreaker[T](
body: Callable[Future[T]],
defineFailureFn: BiFunction[Optional[T], Optional[Throwable], java.lang.Boolean]): Future[T] = {
val failureFnInScala = CircuitBreaker.convertJavaFailureFnToScala(defineFailureFn)
withCircuitBreaker(body.call, failureFnInScala)
}
/**
* Java API (8) for [[#withCircuitBreaker]].
*
* @param body Call needing protected
* @return [[java.util.concurrent.CompletionStage]] containing the call result or a
* `scala.concurrent.TimeoutException` if the call timed out
*/
def callWithCircuitBreakerCS[T](body: Callable[CompletionStage[T]]): CompletionStage[T] =
callWithCircuitBreakerCS(body, CircuitBreaker.exceptionAsFailureJava)
/**
* Java API (8) for [[#withCircuitBreaker]].
*
* @param body Call needing protected
* @param defineFailureFn function that define what should be consider failure and thus increase failure count
* @return [[java.util.concurrent.CompletionStage]] containing the call result or a
* `scala.concurrent.TimeoutException` if the call timed out
*/
def callWithCircuitBreakerCS[T](
body: Callable[CompletionStage[T]],
defineFailureFn: BiFunction[Optional[T], Optional[Throwable], java.lang.Boolean]): CompletionStage[T] =
FutureConverters.toJava[T](callWithCircuitBreaker(new Callable[Future[T]] {
override def call(): Future[T] = FutureConverters.toScala(body.call())
}, defineFailureFn))
/**
* Wraps invocations of synchronous calls that need to be protected.
*
* Calls are run in the caller's thread. Because of the synchronous nature of
* this call, the `scala.concurrent.TimeoutException` will only be thrown
* after the body has completed.
*
* Throws java.util.concurrent.TimeoutException if the call timed out.
*
* @param body Call needing protected
* @return The result of the call
*/
def withSyncCircuitBreaker[T](body: => T): T =
withSyncCircuitBreaker(body, CircuitBreaker.exceptionAsFailure)
/**
* Wraps invocations of synchronous calls that need to be protected.
*
* Calls are run in caller's thread. Because of the synchronous nature of
* this call the `scala.concurrent.TimeoutException` will only be thrown
* after the body has completed.
*
* Throws java.util.concurrent.TimeoutException if the call timed out.
*
* @param body Call needing protected
* @param defineFailureFn function that define what should be consider failure and thus increase failure count
* @return The result of the call
*/
def withSyncCircuitBreaker[T](body: => T, defineFailureFn: Try[T] => Boolean): T =
Await.result(
withCircuitBreaker(
try Future.successful(body)
catch { case NonFatal(t) => Future.failed(t) },
defineFailureFn),
callTimeout)
/**
* Java API for [[#withSyncCircuitBreaker]]. Throws [[java.util.concurrent.TimeoutException]] if the call timed out.
*
* @param body Call needing protected
* @return The result of the call
*/
def callWithSyncCircuitBreaker[T](body: Callable[T]): T =
callWithSyncCircuitBreaker(body, CircuitBreaker.exceptionAsFailureJava[T])
/**
* Java API for [[#withSyncCircuitBreaker]]. Throws [[java.util.concurrent.TimeoutException]] if the call timed out.
*
* @param body Call needing protected
* @param defineFailureFn function that define what should be consider failure and thus increase failure count
* @return The result of the call
*/
def callWithSyncCircuitBreaker[T](
body: Callable[T],
defineFailureFn: BiFunction[Optional[T], Optional[Throwable], java.lang.Boolean]): T = {
val failureFnInScala = CircuitBreaker.convertJavaFailureFnToScala(defineFailureFn)
withSyncCircuitBreaker(body.call, failureFnInScala)
}
/**
* Mark a successful call through CircuitBreaker. Sometimes the callee of CircuitBreaker sends back a message to the
* caller Actor. In such a case, it is convenient to mark a successful call instead of using Future
* via [[withCircuitBreaker]]
*/
def succeed(): Unit = {
currentState.callSucceeds()
}
/**
* Mark a failed call through CircuitBreaker. Sometimes the callee of CircuitBreaker sends back a message to the
* caller Actor. In such a case, it is convenient to mark a failed call instead of using Future
* via [[withCircuitBreaker]]
*/
def fail(): Unit = {
currentState.callFails()
}
/**
* Return true if the internal state is Closed. WARNING: It is a "power API" call which you should use with care.
* Ordinal use cases of CircuitBreaker expects a remote call to return Future, as in withCircuitBreaker.
* So, if you check the state by yourself, and make a remote call outside CircuitBreaker, you should
* manage the state yourself.
*/
def isClosed: Boolean = {
currentState == Closed
}
/**
* Return true if the internal state is Open. WARNING: It is a "power API" call which you should use with care.
* Ordinal use cases of CircuitBreaker expects a remote call to return Future, as in withCircuitBreaker.
* So, if you check the state by yourself, and make a remote call outside CircuitBreaker, you should
* manage the state yourself.
*/
def isOpen: Boolean = {
currentState == Open
}
/**
* Return true if the internal state is HalfOpen. WARNING: It is a "power API" call which you should use with care.
* Ordinal use cases of CircuitBreaker expects a remote call to return Future, as in withCircuitBreaker.
* So, if you check the state by yourself, and make a remote call outside CircuitBreaker, you should
* manage the state yourself.
*/
def isHalfOpen: Boolean = {
currentState == HalfOpen
}
/**
* Adds a callback to execute when circuit breaker opens
*
* The callback is run in the [[scala.concurrent.ExecutionContext]] supplied in the constructor.
*
* @param callback Handler to be invoked on state change
* @return CircuitBreaker for fluent usage
*/
def onOpen(callback: => Unit): CircuitBreaker = addOnOpenListener(new Runnable { def run = callback })
/**
* Java API for onOpen
*
* @param callback Handler to be invoked on state change
* @return CircuitBreaker for fluent usage
*/
def addOnOpenListener(callback: Runnable): CircuitBreaker = {
Open.addListener(callback)
this
}
/**
* Adds a callback to execute when circuit breaker transitions to half-open
* The callback is run in the [[scala.concurrent.ExecutionContext]] supplied in the constructor.
*
* @param callback Handler to be invoked on state change
* @return CircuitBreaker for fluent usage
*/
def onHalfOpen(callback: => Unit): CircuitBreaker = addOnHalfOpenListener(new Runnable { def run = callback })
/**
* JavaAPI for onHalfOpen
*
* @param callback Handler to be invoked on state change
* @return CircuitBreaker for fluent usage
*/
def addOnHalfOpenListener(callback: Runnable): CircuitBreaker = {
HalfOpen.addListener(callback)
this
}
/**
* Adds a callback to execute when circuit breaker state closes
*
* The callback is run in the [[scala.concurrent.ExecutionContext]] supplied in the constructor.
*
* @param callback Handler to be invoked on state change
* @return CircuitBreaker for fluent usage
*/
def onClose(callback: => Unit): CircuitBreaker = addOnCloseListener(new Runnable { def run = callback })
/**
* JavaAPI for onClose
*
* @param callback Handler to be invoked on state change
* @return CircuitBreaker for fluent usage
*/
def addOnCloseListener(callback: Runnable): CircuitBreaker = {
Closed.addListener(callback)
this
}
/**
* Adds a callback to execute when call finished with success.
*
* The callback is run in the [[scala.concurrent.ExecutionContext]] supplied in the constructor.
*
* @param callback Handler to be invoked on successful call, where passed value is elapsed time in nanoseconds.
* @return CircuitBreaker for fluent usage
*/
def onCallSuccess(callback: Long => Unit): CircuitBreaker =
addOnCallSuccessListener(new Consumer[Long] {
def accept(result: Long): Unit = callback(result)
})
/**
* JavaAPI for onCallSuccess
*
* @param callback Handler to be invoked on successful call, where passed value is elapsed time in nanoseconds.
* @return CircuitBreaker for fluent usage
*/
def addOnCallSuccessListener(callback: Consumer[Long]): CircuitBreaker = {
successListeners.add(callback)
this
}
/**
* Adds a callback to execute if the call finished with failure.
*
* The callback is run in the [[scala.concurrent.ExecutionContext]] supplied in the constructor.
*
* @param callback Handler to be invoked on failed call, where passed value is elapsed time in nanoseconds.
* @return CircuitBreaker for fluent usage
*/
def onCallFailure(callback: Long => Unit): CircuitBreaker =
addOnCallFailureListener(new Consumer[Long] {
def accept(result: Long): Unit = callback(result)
})
/**
* JavaAPI for onCallFailure.
*
* @param callback Handler to be invoked on failed call, where passed value is elapsed time in nanoseconds.
* @return CircuitBreaker for fluent usage
*/
def addOnCallFailureListener(callback: Consumer[Long]): CircuitBreaker = {
callFailureListeners.add(callback)
this
}
/**
* Adds a callback to execute if a call finished with timeout.
*
* The callback is run in the [[scala.concurrent.ExecutionContext]] supplied in the constructor.
*
* @param callback Handler to be invoked on call finished with timeout, where passed value is elapsed time in nanoseconds.
* @return CircuitBreaker for fluent usage
*/
def onCallTimeout(callback: Long => Unit): CircuitBreaker =
addOnCallTimeoutListener(new Consumer[Long] {
def accept(result: Long): Unit = callback(result)
})
/**
* JavaAPI for onCallTimeout.
*
* @param callback Handler to be invoked on call finished with timeout, where passed value is elapsed time in nanoseconds.
* @return CircuitBreaker for fluent usage
*/
def addOnCallTimeoutListener(callback: Consumer[Long]): CircuitBreaker = {
callTimeoutListeners.add(callback)
this
}
/**
* Adds a callback to execute if call was failed due to open breaker.
*
* The callback is run in the [[scala.concurrent.ExecutionContext]] supplied in the constructor.
*
* @param callback Handler to be invoked on call failed due to open breaker.
* @return CircuitBreaker for fluent usage
*/
def onCallBreakerOpen(callback: => Unit): CircuitBreaker =
addOnCallBreakerOpenListener(new Runnable { def run = callback })
/**
* JavaAPI for onCallBreakerOpen.
*
* @param callback Handler to be invoked on call failed due to open breaker.
* @return CircuitBreaker for fluent usage
*/
def addOnCallBreakerOpenListener(callback: Runnable): CircuitBreaker = {
callBreakerOpenListeners.add(callback)
this
}
/**
* Retrieves current failure count.
*
* @return count
*/
private[akka] def currentFailureCount: Int = Closed.get
/**
* Implements consistent transition between states. Throws IllegalStateException if an invalid transition is attempted.
*
* @param fromState State being transitioning from
* @param toState State being transitioning from
*/
private def transition(fromState: State, toState: State): Unit = {
if (swapState(fromState, toState))
toState.enter()
// else some other thread already swapped state
}
/**
* Trips breaker to an open state. This is valid from Closed or Half-Open states.
*
* @param fromState State we're coming from (Closed or Half-Open)
*/
private def tripBreaker(fromState: State): Unit = transition(fromState, Open)
/**
* Resets breaker to a closed state. This is valid from an Half-Open state only.
*/
private def resetBreaker(): Unit = transition(HalfOpen, Closed)
/**
* Invokes all onSuccess callback handlers.
*
* @param start time in nanoseconds of call invocation
*/
private def notifyCallSuccessListeners(start: Long): Unit = if (!successListeners.isEmpty) {
val elapsed = System.nanoTime() - start
val iterator = successListeners.iterator()
while (iterator.hasNext) {
val listener = iterator.next()
executor.execute(new Runnable {
def run() = listener.accept(elapsed)
})
}
}
/**
* Invokes all onCallFailure callback handlers.
*
* @param start time in nanoseconds of call invocation
*/
private def notifyCallFailureListeners(start: Long): Unit = if (!callFailureListeners.isEmpty) {
val elapsed = System.nanoTime() - start
val iterator = callFailureListeners.iterator()
while (iterator.hasNext) {
val listener = iterator.next()
executor.execute(new Runnable {
def run() = listener.accept(elapsed)
})
}
}
/**
* Invokes all onCallTimeout callback handlers.
*
* @param start time in nanoseconds of call invocation
*/
private def notifyCallTimeoutListeners(start: Long): Unit = if (!callTimeoutListeners.isEmpty) {
val elapsed = System.nanoTime() - start
val iterator = callTimeoutListeners.iterator()
while (iterator.hasNext) {
val listener = iterator.next()
executor.execute(new Runnable {
def run() = listener.accept(elapsed)
})
}
}
/**
* Invokes all onCallBreakerOpen callback handlers.
*/
private def notifyCallBreakerOpenListeners(): Unit = if (!callBreakerOpenListeners.isEmpty) {
val iterator = callBreakerOpenListeners.iterator()
while (iterator.hasNext) {
val listener = iterator.next()
executor.execute(listener)
}
}
/**
* Attempts to reset breaker by transitioning to a half-open state. This is valid from an Open state only.
*/
private def attemptReset(): Unit = transition(Open, HalfOpen)
private val timeoutEx = new TimeoutException("Circuit Breaker Timed out.") with NoStackTrace
private val callFailureListeners = new CopyOnWriteArrayList[Consumer[Long]]
private val callTimeoutListeners = new CopyOnWriteArrayList[Consumer[Long]]
private val callBreakerOpenListeners = new CopyOnWriteArrayList[Runnable]
private val successListeners = new CopyOnWriteArrayList[Consumer[Long]]
/**
* Internal state abstraction
*/
private sealed trait State {
private val listeners = new CopyOnWriteArrayList[Runnable]
/**
* Add a listener function which is invoked on state entry
*
* @param listener listener implementation
*/
def addListener(listener: Runnable): Unit = listeners.add(listener)
/**
* Test for whether listeners exist
*
* @return whether listeners exist
*/
private def hasListeners: Boolean = !listeners.isEmpty
/**
* Notifies the listeners of the transition event via a Future executed in implicit parameter ExecutionContext
*
* @return Promise which executes listener in supplied [[scala.concurrent.ExecutionContext]]
*/
protected def notifyTransitionListeners(): Unit = {
if (hasListeners) {
val iterator = listeners.iterator
while (iterator.hasNext) {
val listener = iterator.next
executor.execute(listener)
}
}
}
/**
* Shared implementation of call across all states. Thrown exception or execution of the call beyond the allowed
* call timeout is counted as a failed call, otherwise a successful call
*
* @param body Implementation of the call
* @param defineFailureFn function that define what should be consider failure and thus increase failure count
* @return Future containing the result of the call
*/
def callThrough[T](body: => Future[T], defineFailureFn: Try[T] => Boolean): Future[T] = {
def materialize[U](value: => Future[U]): Future[U] =
try value
catch { case NonFatal(t) => Future.failed(t) }
if (callTimeout == Duration.Zero) {
val start = System.nanoTime()
val f = materialize(body)
f.onComplete {
case _: Success[_] =>
notifyCallSuccessListeners(start)
callSucceeds()
case Failure(_) =>
notifyCallFailureListeners(start)
callFails()
}
f
} else {
val start = System.nanoTime()
val p = Promise[T]()
p.future.onComplete { fResult =>
if (defineFailureFn(fResult)) {
callFails()
} else {
notifyCallSuccessListeners(start)
callSucceeds()
}
}(parasitic)
val timeout = scheduler.scheduleOnce(callTimeout) {
if (p.tryFailure(timeoutEx)) {
notifyCallTimeoutListeners(start)
}
}(parasitic)
materialize(body).onComplete {
case Success(result) =>
p.trySuccess(result)
timeout.cancel()
case Failure(ex) =>
if (p.tryFailure(ex)) {
notifyCallFailureListeners(start)
}
timeout.cancel()
}(parasitic)
p.future
}
}
/**
* Shared implementation of call across all states. Thrown exception or execution of the call beyond the allowed
* call timeout is counted as a failed call, otherwise a successful call
*
* @param body Implementation of the call
* @return Future containing the result of the call
*/
def callThrough[T](body: => Future[T]): Future[T] = callThrough(body, CircuitBreaker.exceptionAsFailure)
/**
* Abstract entry point for all states
*
* @param body Implementation of the call that needs protected
* @param defineFailureFn function that define what should be consider failure and thus increase failure count
* @return Future containing result of protected call
*/
def invoke[T](body: => Future[T], defineFailureFn: Try[T] => Boolean): Future[T]
/**
* Abstract entry point for all states
*
* @param body Implementation of the call that needs protected
* @return Future containing result of protected call
*/
def invoke[T](body: => Future[T]): Future[T] = invoke(body, CircuitBreaker.exceptionAsFailure)
/**
* Invoked when call succeeds
*
*/
def callSucceeds(): Unit
/**
* Invoked when call fails
*
*/
def callFails(): Unit
/**
* Invoked on the transitioned-to state during transition. Notifies listeners after invoking subclass template
* method _enter
*
*/
final def enter(): Unit = {
_enter()
notifyTransitionListeners()
}
/**
* Template method for concrete traits
*
*/
def _enter(): Unit
}
/**
* Concrete implementation of Closed state
*/
private object Closed extends AtomicInteger with State {
/**
* Implementation of invoke, which simply attempts the call
*
* @param body Implementation of the call that needs protected
* @return Future containing result of protected call
*/
override def invoke[T](body: => Future[T], defineFailureFn: Try[T] => Boolean): Future[T] =
callThrough(body, defineFailureFn)
/**
* On successful call, the failure count is reset to 0
*
* @return
*/
override def callSucceeds(): Unit = set(0)
/**
* On failed call, the failure count is incremented. The count is checked against the configured maxFailures, and
* the breaker is tripped if we have reached maxFailures.
*
* @return
*/
override def callFails(): Unit = if (incrementAndGet() == maxFailures) tripBreaker(Closed)
/**
* On entry of this state, failure count and resetTimeout is reset.
*
* @return
*/
override def _enter(): Unit = {
set(0)
swapResetTimeout(currentResetTimeout, resetTimeout)
}
/**
* Override for more descriptive toString
*
* @return
*/
override def toString: String = "Closed with failure count = " + get()
}
/**
* Concrete implementation of half-open state
*/
private object HalfOpen extends AtomicBoolean(true) with State {
/**
* Allows a single call through, during which all other callers fail-fast. If the call fails, the breaker reopens.
* If the call succeeds the breaker closes.
*
* @param body Implementation of the call that needs protected
* @return Future containing result of protected call
*/
override def invoke[T](body: => Future[T], defineFailureFn: Try[T] => Boolean): Future[T] =
if (compareAndSet(true, false))
callThrough(body, defineFailureFn)
else {
notifyCallBreakerOpenListeners()
Future.failed[T](new CircuitBreakerOpenException(0.seconds))
}
/**
* Reset breaker on successful call.
*
* @return
*/
override def callSucceeds(): Unit = resetBreaker()
/**
* Reopen breaker on failed call.
*
* @return
*/
override def callFails(): Unit = tripBreaker(HalfOpen)
/**
* On entry, guard should be reset for that first call to get in
*
* @return
*/
override def _enter(): Unit = set(true)
/**
* Override for more descriptive toString
*
* @return
*/
override def toString: String = "Half-Open currently testing call for success = " + get()
}
/**
* Concrete implementation of Open state
*/
private object Open extends AtomicLong with State {
/**
* Fail-fast on any invocation
*
* @param body Implementation of the call that needs protected
* @return Future containing result of protected call
*/
override def invoke[T](body: => Future[T], defineFailureFn: Try[T] => Boolean): Future[T] = {
notifyCallBreakerOpenListeners()
Future.failed(new CircuitBreakerOpenException(remainingDuration()))
}
/**
* Calculate remaining duration until reset to inform the caller in case a backoff algorithm is useful
*
* @return duration to when the breaker will attempt a reset by transitioning to half-open
*/
private def remainingDuration(): FiniteDuration = {
val fromOpened = System.nanoTime() - get
val diff = currentResetTimeout.toNanos - fromOpened
if (diff <= 0L) Duration.Zero
else diff.nanos
}
/**
* No-op for open, calls are never executed so cannot succeed or fail
*
* @return
*/
override def callSucceeds(): Unit = ()
/**
* No-op for open, calls are never executed so cannot succeed or fail
*
* @return
*/
override def callFails(): Unit = ()
/**
* On entering this state, schedule an attempted reset via [[akka.actor.Scheduler]] and store the entry time to
* calculate remaining time before attempted reset.
*
* @return
*/
override def _enter(): Unit = {
set(System.nanoTime())
scheduler.scheduleOnce(currentResetTimeout) {
attemptReset()
}
val nextResetTimeout = currentResetTimeout * exponentialBackoffFactor match {
case f: FiniteDuration => f
case _ => currentResetTimeout
}
if (nextResetTimeout < maxResetTimeout)
swapResetTimeout(currentResetTimeout, nextResetTimeout)
}
/**
* Override for more descriptive toString
*
* @return
*/
override def toString: String = "Open"
}
}
/**
* Exception thrown when Circuit Breaker is open.
*
* @param remainingDuration Stores remaining time before attempting a reset. Zero duration means the breaker is
* currently in half-open state.
* @param message Defaults to "Circuit Breaker is open; calls are failing fast"
*/
class CircuitBreakerOpenException(
val remainingDuration: FiniteDuration,
message: String = "Circuit Breaker is open; calls are failing fast")
extends AkkaException(message)
with NoStackTrace
