Thanks Endre and Roland! Yes, when I add a buffer just before zip.in0, both tests pass:
unzip.out0.buffer(10, OverflowStrategy.backpressure) ~> zip.in0 So, adding the buffer is enabling the parallelism. However, why does not the first test (the one without zip/unzip) need a buffer to enable parallelism (e.g., just before merge)? Thanks, Anil On Wed, Dec 21, 2016 at 2:40 AM, Endre Varga <endre.va...@lightbend.com> wrote: > Yes, that might be the case. > > On Wed, Dec 21, 2016 at 9:39 AM, Roland Kuhn <goo...@rkuhn.info> wrote: > >> I think what is happening here is that zip does not pull until the >> delayed element has come out, meaning that the second (less delayed) >> element will not overtake it. mapAsync is effectively a buffer, so you'll >> need a buffer in front of zip.in0 as well to enable parallelism. >> >> Regards, Roland >> >> Sent from my iPhone >> >> On 21 Dec 2016, at 09:34, Endre Varga <endre.va...@lightbend.com> wrote: >> >> >> >> On Tue, Dec 20, 2016 at 11:34 PM, Anil Gursel <anilgur...@gmail.com> >> wrote: >> >>> I see that unzip does not pull the next element when fusing is on. I >>> understand that when fusing is on, a message goes through the entire stream >>> and then the next message goes through. >>> >> >> This is not true, messages are handled concurrently even in fused >> islands, it is just that they are not parallel. I.e. same thread, but event >> order is unspecified. In fact, fused islands are fair in that even in the >> case of long-running cycles other parts of the graph can still progress >> (which would not be true if what you said would be true) >> >> >>> However, is it still the case when `mapAsyncUnordered` is used? >>> >> >> mapAsync wait on asynchronous events, so that needs to wait until those >> are ready. In the meantime the rest of the graph can progress. >> >> >>> >>> Please see the two tests at https://gist.github.com/ani >>> lgursel/aa70497a9431fc8b498c599d9d469e2b. The two tests are identical >>> except the second one does an unzip then a zip. The first one succeeds and >>> the second one fails. The first one succeeding means that when >>> `mapAsyncUnordered` is used, it is not actually waiting for the previous >>> message to go through the entire stream. >>> >> >> Again, there is no "previous message go through the entire stream". That >> would lead to starving scenarios that you describe. What fusing changes is >> that it removes buffers and hence prefetches. Try out higher delays and see >> what happens. >> >> -Endre >> >> >> >>> >>> I will appreciate if you can shed some light on what's going on in this >>> samples. >>> >>> Thanks, >>> Anil >>> >>> -- >>> >>>>>>>>>> Read the docs: http://akka.io/docs/ >>> >>>>>>>>>> Check the FAQ: http://doc.akka.io/docs/akka/c >>> urrent/additional/faq.html >>> >>>>>>>>>> Search the archives: https://groups.google.com/grou >>> p/akka-user >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Akka User List" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to akka-user+unsubscr...@googlegroups.com. >>> To post to this group, send email to akka-user@googlegroups.com. >>> Visit this group at https://groups.google.com/group/akka-user. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- >> >>>>>>>>>> Read the docs: http://akka.io/docs/ >> >>>>>>>>>> Check the FAQ: http://doc.akka.io/docs/akka/c >> urrent/additional/faq.html >> >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user >> --- >> You received this message because you are subscribed to the Google Groups >> "Akka User List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to akka-user+unsubscr...@googlegroups.com. >> To post to this group, send email to akka-user@googlegroups.com. >> Visit this group at https://groups.google.com/group/akka-user. >> For more options, visit https://groups.google.com/d/optout. >> >> -- >> >>>>>>>>>> Read the docs: http://akka.io/docs/ >> >>>>>>>>>> Check the FAQ: http://doc.akka.io/docs/akka/c >> urrent/additional/faq.html >> >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user >> --- >> You received this message because you are subscribed to the Google Groups >> "Akka User List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to akka-user+unsubscr...@googlegroups.com. >> To post to this group, send email to akka-user@googlegroups.com. >> Visit this group at https://groups.google.com/group/akka-user. >> For more options, visit https://groups.google.com/d/optout. >> > > -- > >>>>>>>>>> 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 > --- > You received this message because you are subscribed to the Google Groups > "Akka User List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to akka-user+unsubscr...@googlegroups.com. > To post to this group, send email to akka-user@googlegroups.com. > Visit this group at https://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/d/optout. > -- >>>>>>>>>> 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 --- You received this message because you are subscribed to the Google Groups "Akka User List" group. 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