Hi Reid, > yout) with exactly one input and output port that is not wired to anything. > > > Okay, just to be clear, GraphBackedFlow will be gone as will the > Flow.apply method that creates them ? >
GraphBackedFlow will be gone, but the functionality will be there, so you will still be able to create a Flow from a graph. The difference is that internally we won't special case it anymore. > > > Okay, can I just suggest that “Module” might be a poor choice for a name > as it is already highly overloaded in lot of other contexts. Node wouldn’t > be much better but choosing good names is a significant aide to > comprehension of these concepts. > Module is an internal name, so you won't see it as a user. What you will observe is a better unification of "boxes with ports" in every layer. -Endre > > > -Endre > > >> >> >> 1. >> -- Eric >> >> >> >> On Thursday, February 12, 2015 at 11:56:03 AM UTC-5, Reid Spencer wrote: >>> >>> hAkkers, >>> >>> I've been unable to *grok <http://en.wikipedia.org/wiki/Grok>* how to >>> communicate with a TCP socket using akka-stream and StreamTcp extension. >>> At this point, I'm not sure the fault is entirely mine. :) I'm building a >>> MongoDB >>> driver <https://github.com/reactific/RxMongo> that uses Akka and I have >>> it working well with akka.io. Mongo requires asynchronous reading and >>> writing on a TCP socket. You can write requests to it as they happen and >>> you read responses as they can be satisfied by the server. Requests and >>> responses are matched with an ID number (i.e. each response indicates the >>> request ID to which it responds). This seems to be an ideal candidate for >>> akka-streams, at least on the surface. I'm now trying to transition my >>> design to use akka-streams and StreamTcp. After several days of fumbling >>> around, I'm still not able to grasp how to connect all the pieces. So, I'm >>> hoping the group can help and that this might be instructive for users of >>> akka-stream, or at least shine some light on needed documentation or >>> features. >>> >>> Just to address the obligatory: >>> >>> - I've read the akka-stream (1.0-M3) documentation, many times, >>> every page. >>> - I've looked at the akka-stream code and discovered that without >>> some sort of internal design document, much of it will be unintelligible >>> because I don't have a conceptual model for how the pieces fit together >>> (essentially a forest/trees issue). >>> - I've read the (insufficient, IMO) API documentation. >>> - I've built, tried and studied the TcpEcho sample program. >>> >>> That sample TcpEcho program is the source of most of my misunderstanding >>> as it is the only sample that relates to what I'm doing and I cannot >>> extrapolate from it to do what I want to do. Here's the program, from >>> the documentation >>> <http://doc.akka.io/docs/akka-stream-and-http-experimental/1.0-M3/scala/stream-io.html#Connecting__REPL_Client> >>> : >>> >>> >>> val connection: OutgoingConnection = StreamTcp().outgoingConnection( >>> localhost) >>> >>> val replParser = new PushStage[String, ByteString] { >>> override def onPush(elem: String, ctx: Context[ByteString]): Directive = >>> { >>> elem match { >>> case "q" ⇒ ctx.pushAndFinish(ByteString("BYE\n")) >>> case _ ⇒ ctx.push(ByteString(s"$elem\n")) >>> } >>> } >>> } >>> >>> val repl = Flow[ByteString] >>> .transform(() => RecipeParseLines.parseLines("\n", maximumLineBytes = >>> 256)) >>> .map(text => println("Server: " + text)) >>> .map(_ => readLine("> ")) >>> .transform(() ⇒ replParser) >>> >>> connection.handleWith(repl) >>> >>> >>> Here are the things that I find confusing: >>> >>> - The repl value is defined by invoking Flow[ByteString]. Now, I >>> know the API well enough to know that Flow requires two type >>> parameters: Flow[+In,-Out] >>> >>> <http://doc.akka.io/api/akka-stream-and-http-experimental/1.0-M3/?_ga=1.17864249.1697328887.1413587984#akka.stream.scaladsl.Flow$> >>> . This is confusing because the Flow companion object's apply method >>> takes only one type argument which it expands by duplicating. So >>> Flow[ByteString] actually instantiates a Flow[ByteString,ByteString]. >>> I only note this because it took some digging around in the API before I >>> understood how this worked and while it is handy, it is also not straight >>> forward. >>> - The documentation implies that a Flow is uni-directional >>> >>> <http://doc.akka.io/docs/akka-stream-and-http-experimental/1.0-M3/scala/stream-flows-and-basics.html#Defining_and_running_streams>. >>> It says a Flow "connects its up- and downstreams by transforming the >>> data elements flowing through it." That, to me, says "unidirectional". >>> The >>> use of a Flow[ByteString,ByteString] for the repl value indicates to >>> me that a uni-directional "transformation" from ByteString to ByteString >>> is >>> occurring and yet this code implies that it is doing both reading and >>> writing to the socket (i.e. it is bi-directional). How can that be? >>> - I see repl as a Flow that does this: takes a ByteString as input, >>> chunks it into \n terminated lines up to 256 bytes, prints those lines >>> out >>> prefixed by "Server: " and then discards that input and replaces it with >>> a >>> line read from the console which is then output with a newline appended >>> unless the input was "q" in which case it is replaced by "BYE\n" and a >>> termination signal. Okay, that's all great and it is all unidirectional >>> writing data to the socket. So, now the questions: >>> - Where is the reading from the server to get the original >>> line(s) as input to the flow? I.e. where is the Source[ByteString]? >>> - Assuming that connection.handleWith(repl)does some magic to set >>> up the Source, how does the conversation get started? Is it assumed >>> the >>> server will send some data upon connection? The echo server >>> example >>> >>> <http://doc.akka.io/docs/akka-stream-and-http-experimental/1.0-M3/scala/stream-io.html#Accepting_connections__Echo_Server> >>> seems to have the same issue! >>> - FYI: OutgoingConnection.handleWith's documentation >>> >>> <http://doc.akka.io/api/akka-stream-and-http-experimental/1.0-M3/?_ga=1.17864249.1697328887.1413587984#akka.stream.scaladsl.StreamTcp$$OutgoingConnection> >>> says this: >>> >>> "Handles the connection using the given flow. This method can be called >>>> several times, every call will materialize the given flow exactly once >>>> thereby triggering a new connection attempt to the remoteAddress. If >>>> the connection cannot be established the materialized stream will >>>> immediately be terminated with a akka.stream.StreamTcpException >>>> <http://doc.akka.io/api/akka-stream-and-http-experimental/1.0-M3/akka/stream/StreamTcpException.html> >>>> ." >>> >>> >>> - It would be nice if there was a little more description around >>> "Handles the connection". Handles it how? Does it set up a Source and >>> Sink? >>> Are asynchronous bi-directional reading from the socket and writing >>> to the >>> socket implied? >>> - Am I to infer from all this that the StreamTcp.outgoingConnection >>> creates a Source[ByteString] from the socket's input and a >>> Sink[ByteString] for the socket's output and that the flow provided >>> to handleWith is run between these two? In other words, the >>> OutgoingConnection can really only transform its input to its >>> output? If so, then: >>> - How is that generally applicable? >>> - This approach works fine for an echo client, but clearly there >>> are protocols where the input and output can and should be processed >>> independently, aren't there? >>> - How would one do what Mongo needs and have an asynch flow of >>> requests that is independent of an asynch flow of responses? >>> - I noticed the Add Bi-directional Flow >>> <https://github.com/akka/akka/issues/16416> issue that is slated >>> for inclusion in 1.0-M4. Is this intended for solving this issue >>> where two >>> related flows are paired to do bi-directional input/output? >>> - Am I just trying to implement my mongo driver before the >>> required features are ready? >>> >>> The documentation says, about this code: >>> >>> A resilient REPL client would be more sophisticated than this, for >>>> example it should split out the input reading into a separate mapAsync step >>>> and have a way to let the server write more data than one ByteString chunk >>>> at any given time, these improvements however are left as exercise for the >>>> reader. >>> >>> >>> I would like a "resilient client" and I think leaving this part as an >>> "exercise for the reader" is asking a bit much from the audience. We need >>> an example of how to do this as it is likely the typical case not the >>> exception (nobody needs another echo server/client). I suspect that the >>> answer to my confusion lies in the information intended but not stated by >>> this sentence from the documentation. >>> >>> Specifically, I do not comprehend how mapAsync (or mapAsyncUnordered) >>> help to split out the input reading because it is NOT obvious to me where >>> this "input reading" is being done! If I used mapAsynch to obtain the >>> request data from my driver's clients, it seems very obtuse to be setting >>> up numerous Futures as opposed to just allowing them to give me a >>> Source[Request] from which their requests are read and processed. >>> >>> Any help you can provide to prevent me from drowning in these waters >>> would be much appreciated!! >>> >>> Thanks, >>> >>> Reid. >>> >> >> -- >> >>>>>>>>>> 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 a topic in the >> Google Groups "Akka User List" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/akka-user/BQhnmseCyN0/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://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 [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://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 a topic in the > Google Groups "Akka User List" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/akka-user/BQhnmseCyN0/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://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 [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://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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