You should be able to allow a faster upstream to continue, while emitting 
the latest value whenever downstream is read with conflate like so:

Source(0 to 1000) 
  .throttle(10, 1.second, 1, ThrottleMode.shaping) // fast upstream
  .conflate((in, prev) => in) // keep the latest value
  .throttle(2, 1.second, 1, ThrottleMode.shaping) // slow downstream 
  .runForeach(println)


--

Johan

Akka Team


On Wednesday, February 7, 2018 at 1:56:11 PM UTC+1, Arnout Engelen wrote:
>
> Hello Saloni,
>
> I think it would be helpful to have a more realistic example than doing 
> "Thread.sleep(1000)" in the sink.
>
> Could we unpack what this sleep is intended to mimic in your 'real' 
> application? Is it for example doing CPU-intensive data parsing or perhaps 
> some kind of IO?
>
>
> Kind regards,
>
> Arnout
>
> On Thu, Jan 25, 2018 at 7:27 AM, <salo...@thoughtworks.com> wrote:
>
>> Hello,
>>
>> We are having a requirement that if a consumer is slower than producer 
>> then discard all the elements that cannot be consumed and whenever the 
>> consumer gets ready, feed the latest element from producer.
>>
>> We tried an approach as follows:
>>
>> Source.actorRef(0, OverflowStrategy.dropHead)       // actor receives 
>>> data at every 10 milliseconds
>>
>> .runWith {
>>>    println("data received")
>>>    Thread.sleep(1000)               // mimic consumer processing data in 
>>> every 1 second
>>> }
>>
>>
>> We shrank the buffer size to 1 (minimal possible) with following settings
>>
>> private val actorMaterializerSettings = ActorMaterializerSettings(
>>> actorSystem).withInputBuffer(1, 1)
>>
>>
>> With this buffer size, Sink pulls data 1 to consume and data 2 to put in 
>> buffer at initialization.
>>
>> While data 1 is getting processed we are dropping data from producer.
>>
>> When data 1 gets processed after 1000 milliseconds (1 second) ideally I 
>> should receive data 10 (and drop 2 - 9 as consumer is slow) but instead I 
>> receive data 2 from the buffer. data 2 in our domain is extremely useless 
>> as it is stale.
>>
>> Is there a way to disable buffer at Sink totally and always pull latest 
>> data from Source ?
>>
>>
>> -- 
>> >>>>>>>>>> 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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>>
>
>
>
> -- 
> Arnout Engelen
> *Senior Software Engineer*
> E: arnout.enge...@lightbend.com
> T: https://twitter.com/raboofje
>
>
>

-- 
>>>>>>>>>>      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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