我想围绕Pubsub主题构建流程
\-----------------------------------------------------\
\ ------------------ ------------ ------------- \
> > wrapWithPublish > > toPubsub | | fromPubsub > >
/ ------------------ ------------ ------------- /
/-----------------------------------------------------/
这是我到目前为止编写的代码
def mediatorFlow[In, Out](mediator: ActorRef, topic: String): Flow[In, Out, Unit] = {
val source =
Source
.actorRef[Out](10, OverflowStrategy.dropHead)
.mapMaterializedValue { ref => mediator ! DistributedPubSubMediator.Subscribe(topic, ref); ref }
val wrapWithPublish =
Flow[In].map(DistributedPubSubMediator.Publish(topic, _))
val unsubscribe = DistributedPubSubMediator.Unsubscribe(topic, ref???)
val toPubsub =
Sink.actorRef[DistributedPubSubMediator.Publish](mediator, unsubscribe)
Flow.fromSinkAndSource(wrapWithPublish to toPubsub, source)
}
问题在于的定义unsubscribe
,我想DistributedPubSubMediator.Subscribe
在流的末尾发送a ,它指定aref
应该是source
上面定义的物化值。
我知道,当Pubsub在流的末尾死亡时,它将自动取消订阅Actor。但是我很好奇无论如何如何解决问题。
为了实现这一点,您将需要构建一个比紧密结合的Flow fromSinkAndSource
,您将需要使用GraphDSL:
val source = ... // as above
Flow.fromGraph(GraphDSL.create(source) { implicit b =>
src =>
import GraphDSL.Implicits._
val concat = b.add(Concat[Any](2))
val wrapWithPublish = b.add(Flow[In].map(DistributedPubSubMediator.Publish(topic, _)))
val toPubSub = b.add(Sink.actorRef[Any](mediator, unsubscribe))
wrapWithPublish ~> concat ~> toPubSub
b.materializedValue.map(DistributedPubSubMediator.Unsubscribe(topic, _)) ~> concat
FlowShape(wrapWithPublish.in, src.out)
})
这样,您可以将其中一部分的物化值注入到流元素的级别中,以使其易于发送给pubsub介体。
本文收集自互联网,转载请注明来源。
如有侵权,请联系[email protected] 删除。
我来说两句