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 <
[email protected]> 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" <[email protected]> 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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>> urrent/additional/faq.html
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> --
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> current/additional/faq.html
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--
Cheers,
√
--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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