scala - 为什么 Akka Streams 会吞下我的异常？

Question

为什么在

import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.stream.scaladsl.Source

object TestExceptionHandling {
  def main(args: Array[String]): Unit = {
    implicit val actorSystem = ActorSystem()
    implicit val materializer = ActorMaterializer()(defaultActorSystem)

    Source(List(1, 2, 3)).map { i =>
      if (i == 2) {
        throw new RuntimeException("Please, don't swallow me!")
      } else {
        i
      }
    }.runForeach { i =>
      println(s"Received $i")
    }
  }
}

默默无视？我可以看到流在打印后停止了 Received 1 ，但没有记录任何内容。请注意，问题通常不是日志配置，因为如果我设置 akka.log-config-on-start = on，我会看到很多输出。在我的 application.conf文件。

Answer 1

我现在使用自定义 Supervision.Decider确保正确记录异常，可以这样设置:

val decider: Supervision.Decider = { e =>
  logger.error("Unhandled exception in stream", e)
  Supervision.Stop
}

implicit val actorSystem = ActorSystem()
val materializerSettings = ActorMaterializerSettings(actorSystem).withSupervisionStrategy(decider)
implicit val materializer = ActorMaterializer(materializerSettings)(actorSystem)

此外，正如 Vikor Klang 所指出的那样，在上面给出的示例中，异常也可以通过“捕获”

Source(List(1, 2, 3)).map { i =>
  if (i == 2) {
    throw new RuntimeException("Please, don't swallow me!")
  } else {
    i
  }
}.runForeach { i =>
  println(s"Received $i")
}.onComplete {
  case Success(_) =>
    println("Done")
  case Failure(e) =>
    println(s"Failed with $e")
}

但是请注意，这种方法不会帮助您

Source(List(1, 2, 3)).map { i =>
  if (i == 2) {
    throw new RuntimeException("Please, don't swallow me!")
  } else {
    i
  }
}.to(Sink.foreach { i =>
  println(s"Received $i")
}).run()

自从 run()返回 Unit .