如何使用Akka HTTP从多个actor / web处理程序正确调用单个服务器？ [英] How to properly call a single server from multiple actors / web handlers using Akka HTTP?

问题描述

我有一个服务（让我们称之为服务A），它使用Akka Server HTTP来处理传入的请求。
此外，我还有第三方应用程序（服务B），它提供了多种Web服务。
服务A的目的是转换客户端请求，调用服务B的一个或多个Web服务，合并/转换结果并将其提供给客户端。

I have a service (let's call it Service A) which uses Akka Server HTTP to handle incoming requests. Also I have 3rd party application (Service B) which provides several web services. The purpose of service A is to transform client requests, call one or multiple web services of service B, merge/transform results and serve it back to a client.

我在某些部分使用Actors，而在其他部分使用Future。
要拨打服务B，我使用Akka HTTP客户端。

I am using Actors for some parts, and just Future for other. To make a call to Service B, I use Akka HTTP client.

Http.get(actorSystem).singleRequest(HttpRequest.create()
        .withUri("http://127.0.0.1:8082/test"), materializer)
        .onComplete(...)

问题是，每个Service A请求都会创建一个新流，如果有多个并发连接，则会产生 akka.stream.OverflowStrategy $ Fail $ BufferOverflowException：超出配置的max-open-请求值[32]错误

The issue is, a new flow is created per each Service A request, and if there are multiple concurrent connections, it results in akka.stream.OverflowStrategy$Fail$BufferOverflowException: Exceeded configured max-open-requests value of [32] error

我已经问过这个问题，并建议使用单个流如何正确调用Akka HTTP客户端多个（10k - 100k）请求？

I already asked this question and got a suggestion to use a single Flow How to properly call Akka HTTP client for multiple (10k - 100k) requests?

虽然它适用于来自一个地方的一批请求，但我不知道如何使用来自我所有并发的单个流请求处理程序。

While it works for a batch of requests coming from a single place, I don't know how to use a single Flow from all my concurrent request handlers.

这样做的正确Akka-way是什么？

What is the correct "Akka-way" to do it?

推荐答案

我认为您可以使用 Source.queue 来缓冲您的请求。下面的代码假设您需要从第三方服务获得答案，因此非常欢迎拥有 Future [HttpResponse] 。这样你也可以提供溢出策略来防止资源匮乏。

I think you could use Source.queue to buffer your requests. The code below assume that you need to get the answer from 3rd party service, so having a Future[HttpResponse] is very welcomed. This way you could also provide an overflow strategy to prevent resource starvation.

import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.model.{HttpRequest, HttpResponse}
import akka.stream.scaladsl.{Keep, Sink, Source}
import akka.stream.{ActorMaterializer, OverflowStrategy}

import scala.concurrent.duration._
import scala.concurrent.{Await, Future, Promise}
import scala.util.{Failure, Success}

import scala.concurrent.ExecutionContext.Implicits.global

implicit val system = ActorSystem("main")
implicit val materializer = ActorMaterializer()
val pool = Http().cachedHostConnectionPool[Promise[HttpResponse]](host = "google.com", port = 80)
val queue = Source.queue[(HttpRequest, Promise[HttpResponse])](10, OverflowStrategy.dropNew)
  .via(pool)
  .toMat(Sink.foreach({
    case ((Success(resp), p)) => p.success(resp)
    case ((Failure(e), p)) => p.failure(e)
  }))(Keep.left)
  .run
val promise = Promise[HttpResponse]
val request = HttpRequest(uri = "/") -> promise

val response = queue.offer(request).flatMap(buffered => {
  if (buffered) promise.future
  else Future.failed(new RuntimeException())
})

Await.ready(response, 3 seconds)

（从我的博客文章）

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