Hi Viktor,
I looked at the Source.tick, but the issue is that `service.getItems` returns a
Future[Seq[Item]] that's why I'm using Source.unfoldAsync. How would this work
wrt Future[Seq[Item]]? BTW, considering it's late where you are, you don't need
to respond immediately ;)
- Drew
> On Dec 30, 2016, at 3:11 PM, Viktor Klang <viktor.kl...@gmail.com> wrote:
>
> How about something like this?
>
> Source.repeat(NotUsed).flatMapConcat { _ =>
> val items = service.getItems
> if (items.isEmpty)
> Source.tick(30.seconds, 1.second, Seq.empty[Item]).take(1).drop(1) // <--
> more than likely easier ways to do this, but it is late here.
> else
> Source.single(items)
> }
>
> On Fri, Dec 30, 2016 at 11:53 PM, Konrad Malawski
> <konrad.malaw...@lightbend.com <mailto:konrad.malaw...@lightbend.com>> wrote:
> Read the docs about GraphStage and custom stream processing elements. It had
> all the utilities needed for this. We also explained them on the Akka blog:
> Akka.io/blog so check that out :)
>
> On Dec 30, 2016 23:29, "Drew Kutcharian" <d...@venarc.com
> <mailto:d...@venarc.com>> wrote:
> Hi,
>
> I have a use case where I poll a datasource for items and as long as there
> are items present I process them as quickly as possible, but when there are
> no items, I would like to poll every X seconds. Is there a built-in construct
> in Akka Streams that I can use?
>
> I'm currently using `Source.unfoldAsync` to get the records from the data
> source. One "bad" option is to just call `Thread.sleep(XXX)` inside
> `Source.unfoldAsync` when the datasource returns no results (as demonstrated
> below), but I want to see if there's a better option.
>
> Source.unfoldAsync[NotUsed, Seq[Item]](NotUsed) { _ =>
> service.getItems flatMap { items =>
> if (items.isEmpty) {
> //TODO Fix this!!!
> Thread.sleep(30 * 1000) //30 seconds
> }
> Future.successful(Some((NotUsed, items)))
> }
> }
>
> I can probably improve on the `Thread.sleep(XXX)` by using having some
> "State" object and have smaller waits, but I feel like that's not going to be
> that much better.
>
> Any input is appreciated.
>
> Thanks,
>
> Drew
>
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