How to limit an Akka Stream to execute and send down one message only once per second?

Question

I have an Akka Stream and I want the stream to send messages down stream approximately every second.

I tried two ways to solve this problem, the first way was to mak

Answer 1

You can either put your elements through the throttling flow, which will back pressure a fast source, or you can use combination of tick and zip.

The first solution would be like this:

val veryFastSource =
  Source.fromIterator(() => Iterator.continually(Random.nextLong() % 10000))

val throttlingFlow = Flow[Long].throttle(
  // how many elements do you allow
  elements = 1,
  // in what unit of time
  per = 1.second,
  maximumBurst = 0,
  // you can also set this to Enforcing, but then your
  // stream will collapse if exceeding the number of elements / s
  mode = ThrottleMode.Shaping
)

veryFastSource.via(throttlingFlow).runWith(Sink.foreach(println))

The second solution would be like this:

val veryFastSource =
  Source.fromIterator(() => Iterator.continually(Random.nextLong() % 10000))

val tickingSource = Source.tick(1.second, 1.second, 0) 

veryFastSource.zip(tickingSource).map(_._1).runWith(Sink.foreach(println))