Scala 和 akka-http 休息服务的断路器

Question

我目前正在使用 Akka-HTTP 实现断路器，如下所示：

 def sendMail(entity: MyEntity): ToResponseMarshallable = {

      Thread.sleep(5 * 1000)
      validateEntity(entity).map[ToResponseMarshallable] {
        case (body, subject) if !isEmpty(body, subject) => {
          val mailResponse = sendMail(body, subject)
          OK -> ProcessedEmailMessage(mailResponse)
        }
        case _ =>
          BadRequest -> s"error: for $entity".toJson
      }
    } catch {
      case e: DeserializationException => HttpResponse(BadRequest).withEntity(HttpEntity(s"error:${e.msg}").withContentType(ContentTypes.`application/json`))
    }
  }

  val maxFailures: Int = 2
  val callTimeout: FiniteDuration = 1 second
  val resetTimeout: FiniteDuration = 30 seconds

  def open: Unit = {
    logger.info("Circuit Breaker is open")
  }

  def close: Unit = {
    logger.info("Circuit Breaker is closed")
  }

  def halfopen: Unit = {
    logger.info("Circuit Breaker is half-open, next message goes through")

  private lazy val breaker = CircuitBreaker(
    system.scheduler,
    maxFailures,
    callTimeout,
    resetTimeout
  ).onOpen(open).onClose(close).onHalfOpen(halfopen)

  def routes: Route = {
    logRequestResult("email-service_aggregator_email") {
      pathPrefix("v1") {
        path("sendmail") {
          post {
            entity(as[EmailMessage]) { entity =>
              complete {
                breaker.withCircuitBreaker(Future(sendMail(entity)))
              }
            }
          }
        }
      }
    }
  }

我的问题是，如果我使用 breaker.withCircuitBreaker(Future(sendMail(entity)))，断路器会进入打开状态，但其余响应 returns There was an internal server error 作为响应

如果我改为使用 breaker.withSyncCircuitBreaker(Future(sendMail(entity)))，则断路器永远不会进入打开状态，但它 return 是预期的 HttpResponse

关于如何解决这个问题以触发断路器和 return 正确的 HTTP 响应有什么想法吗？

Answer 1

entity(as[EmailMessage]) { entity => ctx =>
  val withBreaker = breaker.withCircuitBreaker(Future(sendMail(entity)))
  val withErrorHandling = withBreaker.recover {
      case _: CircuitBreakerOpenException => 
        HttpResponse(TooManyRequests).withEntity("Server Busy")
  }
  ctx.complete(withErrorHandling)
}

Answer 2

我将提供另一种可能的解决方案，因为我相信 onComplete 是完成路线时处理 Future 结果的惯用方式：

entity(as[EmailMessage]) { entity =>
  val withBreaker = breaker.withCircuitBreaker(Future(sendMail(entity)))

  onComplete(withBreaker){
    case Success(trm) => 
      complete(trm)

    //Circuit breaker opened handling
    case Failure(ex:CircuitBreakerOpenException) => 
      complete(HttpResponse(TooManyRequests).withEntity("Server Busy"))

    //General exception handling
    case Failure(ex) =>
      complete(InternalServerError)
  }
}

Scala 和 akka-http 休息服务的断路器

Circuit breaker for Scala and akka-http rest service

scala

reactive-programming

akka

akka-http