使用Akka Streams testkit时出现零星的超时故障

时间：2017-08-10 08:16:30

标签： scala concurrency akka akka-stream

每当我尝试使用Akka的Streams测试包时，我都会看到一些奇怪的行为。

我确实定义了以下自定义：

trait PauseFilter[T] {

  def shouldPause(message: T): Boolean
}

trait MessagePauser[T] {

  def pause(message: T): Unit
}

trait MessageUnPauser[T] {

  def unPause: Option[T]
}

object PausableFlow {

  def pausableFlow[T](filter: PauseFilter[T], pauser: MessagePauser[T], unpauser: MessageUnPauser[T]): Flow[T, T, _] =

    Flow.fromGraph(
      GraphDSL.create() { implicit builder: GraphDSL.Builder[NotUsed] =>
        import GraphDSL.Implicits._

        val initialMessagesIn = builder.add(Flow[T])
        val finalMessagesOut = builder.add(Flow[T])
        val unPauserIterator = () => Iterator.continually(unpauser.unPause)
        val unpausedMessages = Source.fromIterator(unPauserIterator).collect { case Some(m) => m }
        val pausedMessagesSink = Sink.foreach(pauser.pause)
        val determineIfPaused = builder.add(Partition[T](2, message => if (filter.shouldPause(message)) 1 else 0))
        val merge = builder.add(Merge[T](2))

        unpausedMessages    ~>    merge
        initialMessagesIn   ~>    merge   ~>    determineIfPaused
                                                determineIfPaused.out(1)    ~>    pausedMessagesSink
                                                determineIfPaused.out(0)    ~>    finalMessagesOut

        FlowShape(initialMessagesIn.in, finalMessagesOut.out)
      }
    )
}

除此之外，我还在流程规范中定义了以下健全性检查测试：

test("a pauser that pauses half the messages should propagate only half the messages and pause the other half") {
  val filter = new PauseFilter[Int] {
    override def shouldPause(m: Int): Boolean = if (m % 2 == 0) true else false
  }

  val unpauser = mock[MessageUnPauser[Int]]
  Mockito.when(unpauser.unPause).thenReturn(None)

  val pauser = mock[MessagePauser[Int]]

  val (pub, sub) = getTestHandles(PausableFlow.pausableFlow[Int](filter, pauser, unpauser))

  sub.request(200)
  1 to 100 foreach pub.sendNext
  1 to 100 filter (m => m % 2 == 1) foreach sub.expectNext
  1 to 100 filter (m => m % 2 == 0) foreach Mockito.verify(pauser, Mockito.times(1)).pause
}

private def getTestHandles[T](flow: Flow[T, T, _]) = 
  TestSource.probe[T]
    .via(flow)
    .toMat(TestSink.probe[T])(Keep.both)
    .run()

正在发生的事情是，我遇到了零星的失败，但有以下异常：

assertion failed: timeout (3 seconds) during expectMsg: 
java.lang.AssertionError: assertion failed: timeout (3 seconds) during expectMsg: 
  at scala.Predef$.assert(Predef.scala:170)
  at akka.testkit.TestKitBase$class.expectMsgPF(TestKit.scala:405)
  at akka.testkit.TestKit.expectMsgPF(TestKit.scala:814)
  at akka.stream.testkit.StreamTestKit$PublisherProbeSubscription.expectRequest(StreamTestKit.scala:716)
  at akka.stream.testkit.TestPublisher$Probe.sendNext(StreamTestKit.scala:173)
  at com.company.stream.pausable.PausableFlowSpec$$anonfun$3$$anonfun$apply$mcV$sp$5.apply(PausableFlowSpec.scala:70)
  at com.company.stream.pausable.PausableFlowSpec$$anonfun$3$$anonfun$apply$mcV$sp$5.apply(PausableFlowSpec.scala:70)
  at scala.collection.immutable.Range.foreach(Range.scala:160)
  at com.company.stream.pausable.PausableFlowSpec$$anonfun$3.apply$mcV$sp(PausableFlowSpec.scala:70)
  at com.company.stream.pausable.PausableFlowSpec$$anonfun$3.apply(PausableFlowSpec.scala:57)
  at com.company.stream.pausable.PausableFlowSpec$$anonfun$3.apply(PausableFlowSpec.scala:57)
  at org.scalatest.Transformer$$anonfun$apply$1.apply$mcV$sp(Transformer.scala:22)
  at org.scalatest.OutcomeOf$class.outcomeOf(OutcomeOf.scala:85)
  at org.scalatest.OutcomeOf$.outcomeOf(OutcomeOf.scala:104)
  at org.scalatest.Transformer.apply(Transformer.scala:22)
  at org.scalatest.Transformer.apply(Transformer.scala:20)
  at org.scalatest.FunSuiteLike$$anon$1.apply(FunSuiteLike.scala:166)
  at org.scalatest.Suite$class.withFixture(Suite.scala:1122)
  at org.scalatest.FunSuite.withFixture(FunSuite.scala:1555)
  at org.scalatest.FunSuiteLike$class.invokeWithFixture$1(FunSuiteLike.scala:163)
  at org.scalatest.FunSuiteLike$$anonfun$runTest$1.apply(FunSuiteLike.scala:175)
  at org.scalatest.FunSuiteLike$$anonfun$runTest$1.apply(FunSuiteLike.scala:175)
  at org.scalatest.SuperEngine.runTestImpl(Engine.scala:306)
  at org.scalatest.FunSuiteLike$class.runTest(FunSuiteLike.scala:175)
  at org.scalatest.FunSuite.runTest(FunSuite.scala:1555)
  at org.scalatest.FunSuiteLike$$anonfun$runTests$1.apply(FunSuiteLike.scala:208)
  at org.scalatest.FunSuiteLike$$anonfun$runTests$1.apply(FunSuiteLike.scala:208)
  at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:413)
  at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:401)
  at scala.collection.immutable.List.foreach(List.scala:392)
  at org.scalatest.SuperEngine.traverseSubNodes$1(Engine.scala:401)
  at org.scalatest.SuperEngine.org$scalatest$SuperEngine$$runTestsInBranch(Engine.scala:396)
  at org.scalatest.SuperEngine.runTestsImpl(Engine.scala:483)
  at org.scalatest.FunSuiteLike$class.runTests(FunSuiteLike.scala:208)
  at org.scalatest.FunSuite.runTests(FunSuite.scala:1555)
  at org.scalatest.Suite$class.run(Suite.scala:1424)
  at org.scalatest.FunSuite.org$scalatest$FunSuiteLike$$super$run(FunSuite.scala:1555)
  at org.scalatest.FunSuiteLike$$anonfun$run$1.apply(FunSuiteLike.scala:212)
  at org.scalatest.FunSuiteLike$$anonfun$run$1.apply(FunSuiteLike.scala:212)
  at org.scalatest.SuperEngine.runImpl(Engine.scala:545)
  at org.scalatest.FunSuiteLike$class.run(FunSuiteLike.scala:212)
  at com.company.stream.pausable.PausableFlowSpec.org$scalatest$BeforeAndAfterAll$$super$run(PausableFlowSpec.scala:16)
  at org.scalatest.BeforeAndAfterAll$class.liftedTree1$1(BeforeAndAfterAll.scala:257)
  at org.scalatest.BeforeAndAfterAll$class.run(BeforeAndAfterAll.scala:256)
  at com.company.stream.pausable.PausableFlowSpec.run(PausableFlowSpec.scala:16)
  at org.scalatest.tools.SuiteRunner.run(SuiteRunner.scala:55)
  at org.scalatest.tools.Runner$$anonfun$doRunRunRunDaDoRunRun$3.apply(Runner.scala:2563)
  at org.scalatest.tools.Runner$$anonfun$doRunRunRunDaDoRunRun$3.apply(Runner.scala:2557)
  at scala.collection.immutable.List.foreach(List.scala:392)
  at org.scalatest.tools.Runner$.doRunRunRunDaDoRunRun(Runner.scala:2557)
  at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1044)
  at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1043)
  at org.scalatest.tools.Runner$.withClassLoaderAndDispatchReporter(Runner.scala:2722)
  at org.scalatest.tools.Runner$.runOptionallyWithPassFailReporter(Runner.scala:1043)
  at org.scalatest.tools.Runner$.run(Runner.scala:883)
  at org.scalatest.tools.Runner.run(Runner.scala)
  at org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.runScalaTest2(ScalaTestRunner.java:138)
  at org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.main(ScalaTestRunner.java:28)

我已经留下了一些代码，只是为了给你一个参考点，这样你就可以将异常与实际代码联系起来了。调用1 to 100 foreach pub.sendNext时抛出异常。我很困惑为什么会发生这种情况，因为没有什么东西会导致这种行为如此耗费时间。也许我在这里遗漏了一些东西。很高兴得到你的意见。

1 个答案:

答案 0 :(得分：0)

问题在于unPausedMessages - 这会导致（表现明智）流。考虑使用以下方法来驯服此调用：

val unpausedMessages = Source
  .tick(FiniteDuration(0, "ms"), FiniteDuration(100, "ms"), unpauser.unPause)
  .collect { case Some(m) => m }

或同等的。

发生的其他事情是，您尝试将许多项目推送到流中而不消耗。 考虑在同时向消费者执行的1 to 100 foreach pub.sendNext内运行Future。

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