我是akka-streams的新手,不知道如何解决这个问题。
我有3个源流按序列ID排序。我想将具有相同ID的值组合在一起。每个流中的值可能丢失或重复。如果一个流是比其他流更快的生产者,它应该得到反压。
( [A-Z])
答案 0 :(得分:0)
这个问题很老,但是我试图找到一个解决方案,但我只遇到了lightbend forum上的难题,但没有遇到可用的用例。因此,我决定实施并在此处发布示例。
我创建了3个来源sourceA
,sourceB
和sourceC
,它们使用.throttle()
以不同的速度发出事件。然后,我创建了一个RunnableGraph
,在其中我使用Merge
合并了源,并根据事件数量的滑动窗口将输出输出到了WindowGroupEventFlow
Flow
上。这是图形:
sourceA ~> mergeShape.in(0)
sourceB ~> mergeShape.in(1)
sourceC ~> mergeShape.in(2)
mergeShape.out ~> windowFlowShape ~> sinkShape
我在源代码中使用的类是这些:
object Domain {
sealed abstract class Z(val id: Int, val value: String)
case class A(override val id: Int, override val value: String = "A") extends Z(id, value)
case class B(override val id: Int, override val value: String = "B") extends Z(id, value)
case class C(override val id: Int, override val value: String = "C") extends Z(id, value)
case class ABC(override val id: Int, override val value: String) extends Z(id, value)
}
这是我创建的用于对事件进行分组的WindowGroupEventFlow
Flow
:
// step 0: define the shape
class WindowGroupEventFlow(maxBatchSize: Int) extends GraphStage[FlowShape[Domain.Z, Domain.Z]] {
// step 1: define the ports and the component-specific members
val in = Inlet[Domain.Z]("WindowGroupEventFlow.in")
val out = Outlet[Domain.Z]("WindowGroupEventFlow.out")
// step 3: create the logic
override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new GraphStageLogic(shape) {
// mutable state
val batch = new mutable.Queue[Domain.Z]
var count = 0
// var result = ""
// step 4: define mutable state implement my logic here
setHandler(in, new InHandler {
override def onPush(): Unit = {
try {
val nextElement = grab(in)
batch.enqueue(nextElement)
count += 1
// If window finished we have to dequeue all elements
if (count >= maxBatchSize) {
println("************ window finished - dequeuing elements ************")
var result = Map[Int, Domain.Z]()
val list = batch.dequeueAll(_ => true).to[collection.immutable.Iterable]
list.foreach { tuple =>
if (result.contains(tuple.id)) {
val abc = result.get(tuple.id)
val value = abc.get.value + tuple.value
val z: Domain.Z = Domain.ABC(tuple.id, value)
result += (tuple.id -> z)
} else {
val z: Domain.Z = Domain.ABC(tuple.id, tuple.value)
result += (tuple.id -> z)
}
}
val finalResult: collection.immutable.Iterable[Domain.Z] = result.map(p => p._2)
emitMultiple(out, finalResult)
count = 0
} else {
pull(in) // send demand upstream signal, asking for another element
}
} catch {
case e: Throwable => failStage(e)
}
}
})
setHandler(out, new OutHandler {
override def onPull(): Unit = {
pull(in)
}
})
}
// step 2: construct a new shape
override def shape: FlowShape[Domain.Z, Domain.Z] = FlowShape[Domain.Z, Domain.Z](in, out)
}
这就是我运行所有内容的方式:
object WindowGroupEventFlow {
def main(args: Array[String]): Unit = {
run()
}
def run() = {
implicit val system = ActorSystem("WindowGroupEventFlow")
import Domain._
val sourceA = Source(List(A(1), A(2), A(3), A(1), A(2), A(3), A(1), A(2), A(3), A(1))).throttle(3, 1 second)
val sourceB = Source(List(B(1), B(2), B(1), B(2), B(1), B(2), B(1), B(2), B(1), B(2))).throttle(2, 1 second)
val sourceC = Source(List(C(1), C(2), C(3), C(4))).throttle(1, 1 second)
// Step 1 - setting up the fundamental for a stream graph
val windowRunnableGraph = RunnableGraph.fromGraph(
GraphDSL.create() { implicit builder =>
import GraphDSL.Implicits._
// Step 2 - create shapes
val mergeShape = builder.add(Merge[Domain.Z](3))
val windowEventFlow = Flow.fromGraph(new WindowGroupEventFlow(5))
val windowFlowShape = builder.add(windowEventFlow)
val sinkShape = builder.add(Sink.foreach[Domain.Z](x => println(s"sink: $x")))
// Step 3 - tying up the components
sourceA ~> mergeShape.in(0)
sourceB ~> mergeShape.in(1)
sourceC ~> mergeShape.in(2)
mergeShape.out ~> windowFlowShape ~> sinkShape
// Step 4 - return the shape
ClosedShape
}
)
// run the graph and materialize it
val graph = windowRunnableGraph.run()
}
}
您可以在输出中看到我如何对具有相同ID的元素进行分组:
sink: ABC(1,ABC)
sink: ABC(2,AB)
************ window finished - dequeuing elements ************
sink: ABC(3,A)
sink: ABC(1,BA)
sink: ABC(2,CA)
************ window finished - dequeuing elements ************
sink: ABC(2,B)
sink: ABC(3,AC)
sink: ABC(1,BA)
************ window finished - dequeuing elements ************
sink: ABC(2,AB)
sink: ABC(3,A)
sink: ABC(1,BA)