Question

我正在使用host-level API with a queue。

  private val (queueSource, connectionPool) = Source.queue[(HttpRequest, Promise[HttpResponse])](queueSize, OverflowStrategy.backpressure).async
    .viaMat(poolFlow)(Keep.both)
    .toMat(
      Sink.foreach({
        case ((Success(resp), p)) =>
          p.success(resp)
        case ((Failure(e), p)) => p.failure(e)
      })
    )(Keep.left)
    .run()

我有很多请求争夺连接池中的连接，但是我收到以下错误：

 java.lang.IllegalStateException: You have to wait for previous offer to be resolved to send another request
    at akka.stream.impl.QueueSource$$anon$1.akka$stream$impl$QueueSource$$anon$$bufferElem(QueueSource.scala:84)
    at akka.stream.impl.QueueSource$$anon$1$$anonfun$1.apply(QueueSource.scala:94)
    at akka.stream.impl.QueueSource$$anon$1$$anonfun$1.apply(QueueSource.scala:91)
    at akka.stream.impl.fusing.GraphInterpreter.runAsyncInput(GraphInterpreter.scala:447)
    at akka.stream.impl.fusing.GraphInterpreterShell$AsyncInput.execute(ActorGraphInterpreter.scala:464)
    at akka.stream.impl.fusing.GraphInterpreterShell.processEvent(ActorGraphInterpreter.scala:559)
    at akka.stream.impl.fusing.ActorGraphInterpreter.akka$stream$impl$fusing$ActorGraphInterpreter$$processEvent(ActorGraphInterpreter.scala:741)
    at akka.stream.impl.fusing.ActorGraphInterpreter$$anonfun$receive$1.applyOrElse(ActorGraphInterpreter.scala:756)
    at akka.actor.Actor$class.aroundReceive(Actor.scala:517)
    at akka.stream.impl.fusing.ActorGraphInterpreter.aroundReceive(ActorGraphInterpreter.scala:666)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:527)
    at akka.actor.ActorCell.invoke(ActorCell.scala:496)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)
    at akka.dispatch.Mailbox.run(Mailbox.scala:224)
    at akka.dispatch.Mailbox.exec(Mailbox.scala:234)
    at akka.dispatch.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at akka.dispatch.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at akka.dispatch.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at akka.dispatch.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

我尝试添加.async但背压仍未启动。上述错误意味着什么以及如何调查此问题？

Answer 1

您已经使用Source对象方法构建Source.queue，因此我不认为可以直接将反压应用于调用queue.offer的任何功能。但是，您的问题可能会以不同的方式解决。

不同的OverflowStrategy

您可以将策略更改为OverflowStrategy.dropHead或OverflowStrategy.dropTail。如果queueSize与queue.offer次调用的比率相比足够大，那么这可能会满足您的需求。

如何启用Source.Queue Backpressure

1 个答案: