Akka-streams - 如何访问流的物化值

Question

我正在学习使用 Akka 流，并且非常喜欢它，但是具体化部分对我来说仍然有些神秘。

引用自http://doc.akka.io/docs/akka-stream-and-http-experimental/snapshot/scala/http/client-side/host-level.html#host-level-api

... trigger the immediate shutdown of a specific pool by calling shutdown() on the HostConnectionPool instance that the pool client flow materializes into

如何获取 HostConnectionPool 实例？

更重要的是，我想大致了解如何访问物化值并执行某些操作或从中检索信息。

提前感谢您提供任何文档指示或解释。

Answer 1

这是通过您问题中提供的 Source.viaMat function. Extending the code example from the link 完成的：

import akka.http.scaladsl.Http.HostConnectionPool
import akka.stream.scaladsl.Keep
import akka.stream.scaladsl.RunnableGraph

val poolClientFlow = Http().cachedHostConnectionPool[Int]("akka.io")

val graph: RunnableGraph[(HostConnectionPool, Future[(Try[HttpResponse], Int)])]  =
  Source.single(HttpRequest(uri = "/") -> 42)
        .viaMat(poolClientFlow)(Keep.right)
        .toMat(Sink.head)(Keep.both)

val (pool, fut) = graph.run()

pool.shutdown()

由于 Source.single 实体化为 Unit，因此 Keep.right 表示要保留 poolClientFlow 实体化的 HostConnectionPool。在 .toMat 函数中，Keep.both 表示让左侧池远离流，右侧 Future 来自 Sink.

Akka-streams - 如何访问流的物化值

Akka-streams - how to access the materialized value of the stream

scala

akka-stream

akka-http