为什么Akka Streams吞没我的例外？ [英] Why is Akka Streams swallowing my exceptions?

问题描述

为什么

中的例外是

  import akka.actor.ActorSystem 
 import akka.stream.ActorMaterializer 
 import akka.stream.scaladsl.Source 
 
对象TestExceptionHandling {
 def main（args：Array [String]）：Unit = {
 implicit val actorSystem = ActorSystem（） 
隐式val物质= ActorMaterializer（）（defaultActorSystem）
 
源（列表（1，2，3））。map {i => 
 if（i == 2）{
 throw new RuntimeException（请不要吞下我！）
} else {
i 
} 
} .runForeach {i => 
 println（sReceived $ i）
} 
} 
} 
  

默认忽略？我可以看到，在打印收到1 之后，流被停止，但没有记录。请注意，问题不在于一般的日志配置，因为我在 akka.log-config-on-start = on 在我的 application.conf file。

解决方案

我正在使用自定义 Supervision.Decider ，确保正常记录了异常，可以这样设置：

  val decider：Supervision.Decider = {e => 
 logger.error（未处理的异常流，e）
 Supervision.Stop 
} 
 
隐式val actorSystem = ActorSystem（）
 val materializerSettings = ActorMaterializerSettings（actorSystem）.withSupervisionStrategy（decider）
 implicit val materializer = ActorMaterializer（materializerSettings）（actorSystem）
  

另外，正如维柯巴生所指出的，在上面给出的例子中，例外情况也可以通过

  Source（List（1，2，3））抓住map {i => 
 if（i == 2）{
 throw new RuntimeException（请不要吞下我！）
} else {
i 
} 
} .runForeach {i => 
 println（sReceived $ i）
} .onComplete {
 case Success（_）=> 
 println（Done）
 case Failure（e）=> 
 println（sFailed with $ e）
} 
  

，这种方法不会帮助你使用

  Source（List（1，2，3））。map {i = > 
 if（i == 2）{
 throw new RuntimeException（请不要吞下我！）
} else {
i 
} 
} .to（Sink.foreach {i => 
 println（sReceived $ i）
}）。run（）
   run（）返回单位。 
Why is the exception in
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")
    }
  }
}
silently ignored? I can see that the stream gets stopped after printing Received 1, but nothing is logged. Note that the problem is not the logging configuration in general, as I see a lot of output if I set akka.log-config-on-start = on in my application.conf file.
解决方案
I'm now using a custom Supervision.Decider that makes sure exceptions are properly logged, that can be set up like this:
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)
Also, as has been pointed out by Vikor Klang, in the example given above, the exception could also be "caught" via
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")
}
Note however, that this approach won't help you with
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()
since run() returns Unit.

                        
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