Akka Streams 拆分 Stream 以进行错误处理

Question

我正在使用 akka http 和流来满足 API 请求。当请求无效时，我想 return 一个 400，如果它有效，我想继续计算，然后 return 结果。我面临的问题是，我从 POST 请求收到的有效负载是一个源，我无法将其转换为 2 个流（一个用于有效输入数据，一个用于无效输入数据）并正确完成请求.

path("alarms")(
  post(entity(asSourceOf[String]) { message =>
    val flow = message.via(Flow[String].map((it) => 
         Try(if valid(it) then it else throw Exception("Wrong input"))
    ))
    complete(repository.create(flow).run) // <-- here I only want to pass all events that are valid. For the other events complete(HttpResponse(NotFound, entity = "Invalid input")) should be used
  })
)
/// The signature of the repository.create looks like that
def create(message: Source[String, NotUsed]): RunnableGraph[Future[Done]]

Answer 1

你可以使用 akka-http handleExceptions 指令，像这样：

val exceptionHandler = ExceptionHandler {
 case ex: RuntimeException =>
   complete(HttpResponse(NotFound, entity = "Invalid input"))
}

path("alarms")(
  handleExceptions(exceptionHandler) {
    post(entity(asSourceOf[String]) { message =>
      val flow = message.via(Flow[String].map((it) =>
        Try(if valid(it) then it else throw new RuntimeException("Invalid input"))
      ))
      complete(repository.create(flow).run)
  })
  }
)

文档：

https://doc.akka.io/docs/akka-http/current/routing-dsl/directives/execution-directives/handleExceptions.html

https://doc.akka.io/docs/akka-http/current/routing-dsl/exception-handling.html

还有 handleRejections 指令可以进行更多控制 - 请参阅 https://doc.akka.io/docs/akka-http/current/routing-dsl/directives/execution-directives/handleRejections.html

Akka Streams 拆分 Stream 以进行错误处理

Akka Streams split Stream for Error handling

scala

akka

reactive-programming

akka-stream

akka-http