> there is no reference to PowerPoint in my email, what are you referring to?
I was referring to the following statement from your previous email: Agreed, they don't come with the proper power level labelling at the moment. If on the other hand you want to dive deep into Streams... I do want to understand the nuts and bolts. I read the design concepts behind Akka Streams and other than backpressure, it didn't feel very unfamiliar. Cascading for example, that builds on Hadoop, not unlike Akka Streams builds on Akka actors, has remarkably similar design, including the plumbing and data flow analogy. Regards On Monday, October 5, 2015 at 12:13:47 AM UTC-7, rkuhn wrote: > > Hi Abhijit, > > there is no reference to PowerPoint in my email, what are you referring to? > > Your question will be answered by reading these docs > <http://doc.akka.io/docs/akka-stream-and-http-experimental/1.0/scala/stream-rate.html>. > > What I meant to convey is that the internal handling of demand generation > is an implementation detail that almost all Akka Streams usage should not > care about, the whole point of the library is to solve this problem on your > behalf to free up your time for more interesting things. If on the other > hand you want to dive deep into Streams, please do read all the > documentation (including the design goals and the cookbook). > > Regards, > > Roland > > 5 okt 2015 kl. 09:05 skrev Abhijit Sarkar <[email protected] > <javascript:>>: > > I don't understand the reference to Power Point and I disagree with you > regarding the test drive example. The internet is full of such "test drive" > examples with people doubling integers using Akka streams. If I really > wanted to do that, I'd not need a new library. > Since you didn't answer my question I request that you direct me to any > source of information that's relevant to my question, which is how the > initial demand is generated. > > Regards, > Abhijit > > On Sunday, October 4, 2015 at 11:59:46 PM UTC-7, √ wrote: > > > > On Mon, Oct 5, 2015 at 8:49 AM, Roland Kuhn <[email protected]> wrote: > > Hi Abhijit, > > perhaps it might make sense to test drive the car a little bit before > popping the hood and fiddling with the engine: formulate a few flows > without ActorPublisher and ActorSubscriber and get a feel for how Akka > Streams really is about declarative data flow. Interfacing with regular > Actors means having to learn lots about the underlying mechanics—and most > of the time you won’t need that. > > Note to self: we need to de-emphasize ActorPublisher/Subscriber *a lot* and > tell people that that is a last resort kind of special low-level tool. > > > Agreed, they don't come with the proper power level labelling at the > moment. > > > > Regards, > > Roland > > 5 okt 2015 kl. 07:22 skrev Abhijit Sarkar <[email protected]>: > > I'm cutting my teeth on Akka streams and did a fibonacci > publisher-subscriber example as follows. However, I don't quite understand > yet how the demand is initially generated and what relation it has with the > subscriber's request strategy. Can someone please explain? > > Full Disclosure: I'd posted this question on SO > <http://stackoverflow.com/questions/32930053/akka-scala-can-you-explain-whats-going-on-in-this-akka-streams-flow> > > but didn't received an answer. > > FibonacciPublisher: > > lass FibonacciPublisher extends ActorPublisher[Long] with ActorLogging { > private val queue = Queue[Long](0, 1) > > def receive = { > case Request(_) => // _ is the demand > log.debug("Received request; demand = {}.", totalDemand) > publish > case Cancel => > log.info("Stopping.") > context.stop(self) > case unknown => log.warning("Received unknown event: {}.", unknown) > } > > final def publish = { > while (isActive && totalDemand > 0) { > val next = queue.head > queue += (queue.dequeue + queue.head) > > log.debug("Producing fibonacci number: {}.", next) > > onNext(next) > > if (next > 5000) self ! Cancel > } > }} > > > FibonacciSubscriber: > > class FibonacciSubscriber extends ActorSubscriber with ActorLogging { > val requestStrategy = WatermarkRequestStrategy(20) > > def receive = { > case OnNext(fib: Long) => > log.debug("Received Fibonacci number: {}", fib) > > if (fib > 5000) self ! OnComplete > case OnError(ex: Exception) => > log.error(ex, ex.getMessage) > self ! OnComplete > case OnComplete => > log.info("Fibonacci stream completed.") > context.stop(self) > case unknown => log.warning("Received unknown event: {}.", unknown) > }} > > > Fibonacci App: > > val src = Source.actorPublisher(Props[FibonacciPublisher])val flow = > Flow[Long].map { _ * 2 }val sink = > Sink.actorSubscriber(Props[FibonacciSubscriber]) > > src.via(flow).runWith(sink) > > > Sample run: *Question: Where did the initial demand for 4 come from?* > > 2015-10-03 23:10:49.120 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Received request; demand = 4.2015-10-03 > 23:10:49.120 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Producing fibonacci number: 0.2015-10-03 > 23:10:49.121 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Producing fibonacci number: 1.2015-10-03 > 23:10:49.121 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Producing fibonacci number: 1.2015-10-03 > 23:10:49.121 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Producing fibonacci number: 2.2015-10-03 > 23:10:49.122 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciSubscriber - Received Fibonacci number: 02015-10-03 > 23:10:49.122 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciSubscriber - Received Fibonacci number: 22015-10-03 > 23:10:49.123 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Received request; demand = 2.2015-10-03 > 23:10:49.123 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciSubscriber - Received Fibonacci number: 22015-10-03 > 23:10:49.124 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciSubscriber - Received Fibonacci number: 42015-10-03 > 23:10:49.124 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Producing fibonacci number: 3.2015-10-03 > 23:10:49.125 [fibonacci-akka.actor.default-dispatcher-2] [DEBUG] > n.a.s.f.FibonacciProducer - Producing fibonacci number: 5. > > > > > -- > >>>>>>>>>> Read the docs: http://akka.io/docs/ > >>>>>>>>>> Check the FAQ: > > ... -- >>>>>>>>>> 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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