Monix：InputStreamObservable 不支持多个订阅者

Question

我正在尝试将 (String, Date) 的 Observable 拆分为两个不同的 Observable，并将它们压缩在一起，如下所示

import monix.execution.Scheduler.Implicits.global
val x = Observable.fromIterator((0 to 10).map(i => (s"a $i", s"b $i")).toIterator)

val y = Observable.toReactive(x)

val fileStream = Observable.fromReactivePublisher(y).mapAsync(5)(a => Task{println(a._1); a._1})
val dateStream = Observable.fromReactivePublisher(y).mapAsync(5)(a => Task{println(a._2); a._2})

fileStream.zip(dateStream)
  .map(println)
  .subscribe()

但我收到以下异常

monix.reactive.exceptions.MultipleSubscribersException: InputStreamObservable does not support multiple subscribers
    at monix.reactive.exceptions.MultipleSubscribersException$.build(MultipleSubscribersException.scala:51)
    at monix.reactive.internal.builders.IteratorAsObservable.unsafeSubscribeFn(IteratorAsObservable.scala:42)
    at monix.reactive.Observable$$anon.subscribe(Observable.scala:155)
    at monix.reactive.internal.builders.ReactiveObservable.unsafeSubscribeFn(ReactiveObservable.scala:38)
    at monix.reactive.internal.operators.MapAsyncParallelObservable.unsafeSubscribeFn(MapAsyncParallelObservable.scala:60)
    at monix.reactive.internal.builders.Zip2Observable.unsafeSubscribeFn(Zip2Observable.scala:158)
    at monix.reactive.Observable$$anon.unsafeSubscribeFn(Observable.scala:139)
    at monix.reactive.Observable$class.subscribe(Observable.scala:71)
    at monix.reactive.Observable$$anon.subscribe(Observable.scala:136)
    at monix.reactive.Observable$class.subscribe(Observable.scala:90)
    at monix.reactive.Observable$$anon.subscribe(Observable.scala:136)
    at monix.reactive.Observable$class.subscribe(Observable.scala:120)
    at monix.reactive.Observable$$anon.subscribe(Observable.scala:136)
    at monix.reactive.Observable$class.subscribe(Observable.scala:112)
    at monix.reactive.Observable$$anon.subscribe(Observable.scala:136)

Answer 1

转换 to/from 反应式是强制性的吗？

修复它的一种方法是 val x = Observable.fromIterable((0 to 10).map(i => (s"a $i", s"b $i")))，但是对于无限流它会出现 OutOfMemoryError。

另一种方法是使用.multicast(Pipe.publish[])然后obs.connect()下代码：

import monix.execution.Scheduler.Implicits.global
val x = Observable.fromIterator((0 to 10).map(i => (s"a $i", s"b $i")).iterator)

val y = Observable.toReactive(x)
val obsY = Observable.fromReactivePublisher(y)
val connectY = obsY.multicast(Pipe.publish[(String, String)])

val fileStream = connectY.mapAsync(5)(a => Task{println(a._1); a._1})
val dateStream = connectY.mapAsync(5)(a => Task{println(a._2); a._2})

fileStream.zip(dateStream)
  .map(println)
  .subscribe()

connectY.connect()

Thread.sleep(5000)

Answer 2

除了 sergei-shubin 的回答之外，还可以暂时将 Observable 转换为 "hot" 可观察对象，可以使用 publishSelector 将其拆分为多个流，而无需手动处理一个multicast。这看起来像：

val x = Observable.fromIterator((0 to 10).map(i => (s"a $i", s"b $i")).toIterator)

val zipped = x.publishSelector { o =>
  val fileStream = o.mapParallelUnordered(5)(a => Task{println(a._1); a._1})
  val dateStream = o.mapParallelUnordered(5)(a => Task{println(a._2); a._2})

  fileStream.zip(dateStream)
}

zipped
  .map(println)
  .subscribe()

Monix：InputStreamObservable 不支持多个订阅者

Monix : InputStreamObservable does not support multiple subscribers

scala

reactive-programming

monix