如何启用Source.Queue背压

本文介绍了如何启用Source.Queue背压的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在使用带有队列的主机级API 。

私有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）}））（保持左） .run（）

我有很多要求争夺连接池，但出现以下错误：

java.lang.IllegalStateException：您必须等待以前的报价被解析为在akka.stream.impl.QueueSource $$ anon $ 1.akka $ stream $ impl $ QueueSource $$ anon $$ bufferElem（QueueSource.scala：84）发送另一个请求akka.stream.impl .QueueSource $$ anon $ 1 $$ anonfun $ 1.apply（QueueSource.scala：94）在akka.stream.impl.QueueSource $$ anon $ 1 $$ anonfun $ 1.apply（QueueSource.scala：91 ）在akka.stream.impl.fusing.GraphInterpreter.runAsyncInput（GraphInterpreter.scala：447）在akka.stream.impl.fusing.GraphInterpreterShell $ AsyncInput.execute（ActorGraphInterpreter.scala：464）在akka.stream.impl.fusing.GraphInterpreterShell.processEvent（ActorGraphInterpreter.scala：559）在akka.stream.impl.fusing.ActorGraphInterpreter.akka $ stream $ impl $ fusing $ ActorGraphInterpreter $$ processEvent（ ActorGraphInterpreter.scala：741）在akka.stream.impl.fusing.ActorGraphInterpreter $$ anonfun $ receive $ 1.applyOrElse（ActorGraphInterpreter.scala：756）在akka.actor.Actor $ class.aroundReceive（ Actor.scala：517）在akka.stream.impl.fusing.ActorGraphInterpreter.aroundReceive（ActorGraphInterpreter.scala：666）在akka.actor.ActorCell.receiveMessage（ActorCell.scala：527）在akka.actor.ActorCell.invoke（ActorCell.scala：496）在akka.dispatch.Mailbox.processMailbox（Mailbox.scala：257）在akka.dispatch.Mailbox.run（Mailbox .s cala：224）在akka.dispatch.Mailbox.exec（Mailbox.scala：234）在akka.dispatch.forkjoin.ForkJoinTask.doExec（ForkJoinTask.java:260）在akka .dispatch.forkjoin.ForkJoinPool $ WorkQueue.runTask（ForkJoinPool.java:1339）在akka.dispatch.forkjoin.ForkJoinPool.runWorker（ForkJoinPool.java:1979）在akka.dispatch.forkjoin.ForkJoinWorkerThread .run（ForkJoinWorkerThread.java:107）

我尝试添加.async，但反压力仍然没有解决上面的错误是什么意思，以及如何进行问题研究？

解决方案

您已经在构建 Source 和 Source.queue 对象方法，因此我认为不可能直接对任何功能调用施加反压力 queue.offer 。但是，您的问题可能会以其他方式解决。

不同的 OverflowStrategy

您可以将策略更改为 OverflowStrategy.dropHead 或 OverflowStrategy.dropTail 。如果与 queue.offer 调用的速率相比，您的 queueSize 足够大，则可能会满足您的需求。 / p>

I'm using 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()

I have a lot of request racing for connections in the connection pool but I get the following error:

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)

I tried adding .async but back pressure still does not kick in. What does the error above mean and how to go about investigating the problem?

解决方案

You are already constructing a Source with the Source.queue object method so I don't think it is possible to directly apply back pressure to whatever functionality is calling queue.offer. However, your problem can likely be solved in a different way.

Different OverflowStrategy

You could change the strategy to something like OverflowStrategy.dropHead or OverflowStrategy.dropTail. If your queueSize is large enough compared to the rate of queue.offer invocations then this will probably suite your needs.