[akka-stream] How to emit the newest element every n seconds?

[Dominykas Mostauskis]

In Akka Stream, I'd like a stream with a timer that emits an element every n seconds. The timer should emit from a 1 element buffer that drops head on overflow (meaning only keeps the newest element). So essentially emit the newest element in intervals of n seconds. How can this be done?

My attempts could not get me further than a stream that emits the newest element with a lag of n seconds, meaning the current timer's cycle doesn't sample new elements. It looked something like `in ~> buffer.drophead ~> throttle(1 element/per second)`.

[Martynas Mickevičius]

Hi. You were quite close. Instead of buffer.drophead use conflate which is a rate detached operation. That allows upstream before conflate progress faster than downstream after the conflate.

Source

  .unfold(0) { e => Some((e + 1, e)) }

  .conflate[Int] { case (_, e) => e }

  .throttle(1, 1.second, 1, ThrottleMode.Shaping)

  .runForeach(println)

On Fri, Jul 29, 2016 at 4:27 PM, Dominykas Mostauskis <dominykas....@gmail.com> wrote:

In Akka Stream, I'd like a stream with a timer that emits an element every n seconds. The timer should emit from a 1 element buffer that drops head on overflow (meaning only keeps the newest element). So essentially emit the newest element in intervals of n seconds. How can this be done?

My attempts could not get me further than a stream that emits the newest element with a lag of n seconds, meaning the current timer's cycle doesn't sample new elements. It looked something like `in ~> buffer.drophead ~> throttle(1 element/per second)`.

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