Ah, I think I have the answer that I need, it’s to use getAsyncCallback which allows unrestricted entry to the graph. I didn’t see the connection looking through the source and the docs catch my eye for some reason to start with.
Cheers, Brian > On Jun 12, 2016, at 2:04 AM, Brian Topping <[email protected]> wrote: > > Hi all, I have a very small stream that takes data from a GraphStage and > pushes it to a file: > > val (killSwitch, flow) = dataSource > .viaMat(KillSwitches.single)(Keep.right) > .toMat(FileIO.toPath(Paths.get("/home/brian/test")))(Keep.both) > .run() > > The dataSource is a GraphStage that takes data from a native method that > talks to hardware. There's a fairly large amount of data that comes in > (~1MB/s). The template for the GraphStage is > https://github.com/akka/akka/blob/bd8fcc9d9aeafc2c49745e7519d13b3e0abc18e6/akka-docs/rst/scala/code/docs/stream/GraphStageDocSpec.scala#L48-L68 > with an onPull() that looks like this: > > override def onPull(): Unit = { > if (isAvailable(out)) { > val pulled: ByteString = nativePull() > if (pulled != null) { > push(out, pulled) > } > } > } > > In some cases, nativePull() does not have any data from the device. In that > case, the code does not do a push(). > > I've seen that the GraphStage only gets a single onPull() -- if it does not > return data, the stream stalls. > > What is the correct means to restart the calls to onPull() once it's > determined that a call to nativePull() would be successful? Maybe it's as > simple as the call to nativePull() should block? A Source that has no data > definitely qualifies the entire stream to not idly spin with no data to work > on... > > Thanks! Brian > > -- > >>>>>>>>>> Read the docs: http://akka.io/docs/ <http://akka.io/docs/> > >>>>>>>>>> Check the FAQ: > >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html > >>>>>>>>>> <http://doc.akka.io/docs/akka/current/additional/faq.html> > >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user > >>>>>>>>>> <https://groups.google.com/group/akka-user> > --- > You received this message because you are subscribed to a topic in the Google > Groups "Akka User List" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/akka-user/JlFj8mzvBSA/unsubscribe > <https://groups.google.com/d/topic/akka-user/JlFj8mzvBSA/unsubscribe>. > To unsubscribe from this group and all its topics, send an email to > [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/akka-user > <https://groups.google.com/group/akka-user>. > For more options, visit https://groups.google.com/d/optout > <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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/akka-user. For more options, visit https://groups.google.com/d/optout.
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