Hi,
I'm using Akka Stream M5. I have always been a fan of delayed/lazy
execution, kind of like Akka Stream's source->flow->sink and then run(). So
I created an array to store functions called:
val actionStream: ArrayBuffer[(IntermediateResult) => IntermediateResult] =
ArrayBuffer.empty[(IntermediateResult) => IntermediateResult]
Then I want to use Akka Stream's mapAsync to execute those stored
functions on data, so I wrote this:
protected val source: Source[NormalRow, Unit] = Source(() => data.
dataIterator)
val printSink = Sink.foreach[IntermediateResult](e => save(combine(e._1, e.
_2)))
val sourceReady = if (actionStream.size == 1)
source
.via(Flow[NormalRow]
.mapAsync(e => {println("inside here"); applyHeadFlow(e, actionStream.head
)}))
else
actionStream.drop(1).foldLeft(source
.via(Flow[NormalRow]
.mapAsync(e =>applyHeadFlow(e, actionStream.head)))
){(source, action) =>
source.via(Flow[IntermediateResult].mapAsync(e => Future(action(e))))
}
sourceReady.runWith(printSink)
And as you might notice, there is a discrepancy between the first
action and the subsequent actions (the first works on NormalRow, but the
rest works on IntermediateResult), so I created a helper function:
def applyHeadFlow(row: NormalRow, action: (IntermediateResult) =>
IntermediateResult): Future[IntermediateResult] = Future {
action.apply(row, None)
}
I thought this is already and should be fine, but when I tried to
run it, there is no output generated. So I start putting "println()"
statements inside the mapAsync() or Sink function, but console did not
print anything as well.
Can anyone care to offer somehelp??
Sincerely,
Allen
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