Hi Konrad do you think that creating a "streams adapter" that exposes the current PersistentView as a stream and then switching to the new impl when it's stable would be a good idea?
On Friday, 17 July 2015 10:52:28 UTC+2, Konrad Malawski wrote: > > Hi guys, > A few things to add to the discussion here :-) > > Multiple journals are supported in Akka Persistence since 2.4-M1. > https://github.com/akka/akka/issues/15587 > In general 2.4 will include all the things that were missing in > persistence in its experimental phase. > > >> *Push model:*Akka PersistentViews queries the datasource every 4-5 sek >> by default. If you worry much about the time it takes for propagation and >> do not want to hammer the database for quick updates, you can implement a >> push version of above. Please note that this introduces an extra write for >> the channel. > > Actually this is the Pull model. The PersistentView is pulling from the > datastore. The datastore is not pushing to the view. > > The new query side is actually pretty similar to streamz - it is a streams > (akka streams) based abstraction on querying journals. > Also, these can actually be "push", you could hook up a Source to a pubsub > or eventstream (the akka ones, or different ones) for example. > There will be a PR with it very soon, in general the direction is: > (readJournal.query(...): > Source[Any, _]) so you could .to(someOtherDatabaseSink) > > On Thu, Jul 16, 2015 at 10:28 AM, haghard <hagh...@gmail.com <javascript:> > > wrote: > >> -That looks like a convenient syntax that does the same thing as a >> persistent view does, tailored for users of scalaz streams, or am I missing >> something? >> Yes >> >> -Can you take multiple eventlogs and combine them into one reproducible >> ordered stream. So that if you make decisions (validate preconditions >> against that read model) based on that stream, can you guarantee that the >> next replay up would recreate the same results? I think that is where it >> becomes very tricky. >> >> The order you emit event is all up to you, scalaz-streams provide api for >> this purposes. >> You can build your read order based on some meta data in events or just >> read first available >> For example >> >> https://github.com/haghard/sport-center/blob/b35ccec59c65c674334ff7a1836bb54e829a1ed5/query-side-results/src/main/scala/view/ResultsViewRouter.scala#L43 >> >> >> среда, 15 июля 2015 г., 19:33:19 UTC+3 пользователь Magnus Andersson >> написал: >> >>> Hi >>> >>> Hagard: That looks like a convenient syntax that does the same thing as >>> a persistent view does, tailored for users of scalaz streams, or am I >>> missing something? >>> >>> Can you take multiple eventlogs and combine them into one reproducible >>> ordered stream. So that if you make decisions (validate preconditions >>> against that read model) based on that stream, can you guarantee that the >>> next replay up would recreate the same results? I think that is where it >>> becomes very tricky. >>> >>> /Magnus >>> >>> Den tisdag 14 juli 2015 kl. 13:51:25 UTC+2 skrev haghard: >>>> >>>> >>>> Hi, >>>> >>>> Please take a look at https://github.com/krasserm/streamz >>>> You can read concrete journal with ```replay("processorA")``` and write >>>> in anywhere manually without interaction with PersistentView >>>> >>>> Hope it helps >>>> >>>> вторник, 14 июля 2015 г., 10:20:29 UTC+3 пользователь Amiri Barksdale >>>> написал: >>>>> >>>>> I've been reading up here on PersistentActor, and I think I get how >>>>> that works to perform commands and write the result to an event store. I >>>>> also think I understand that PersistentViews can subscribe to a >>>>> PersistentActor and receive notification of each event stored for that >>>>> PersistentActor type. I want to take a PersistentView and use it to >>>>> update >>>>> a separate Read datastore. >>>>> >>>>> I don't want to treat the PersistentView itself as a read store, but I >>>>> want to make it trigger the creation or updating or saving of a >>>>> "projection" of the event in some other store, like, e.g., Elasticsearch >>>>> or >>>>> Postgresql. Are there any guidelines, best practices, or examples of how >>>>> to >>>>> do this? >>>>> >>>>> One thread ( >>>>> https://groups.google.com/forum/#!searchin/akka-user/persistentview/akka-user/rMHjwBZpocQ/SmfAGMg7G68J) >>>>> >>>>> from June 2014 seemed to indicate that this sort of writing to another >>>>> store would require PersistentViews to be able to read from multiple >>>>> PersistentActors for this to be feasible. Is this still true? >>>>> >>>>> What is the path to take here, to get the actor system populating my >>>>> read stores? Are people instead creating projections directly from the >>>>> event store itself, like Greg Young's EventStore allows? >>>>> >>>>> Any insight is welcome! >>>>> >>>>> Amiri >>>>> >>>> -- >> >>>>>>>>>> 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+...@googlegroups.com <javascript:>. >> To post to this group, send email to akka...@googlegroups.com >> <javascript:>. >> Visit this group at http://groups.google.com/group/akka-user. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > Cheers, > Konrad 'ktoso' Malawski > Akka <http://akka.io/> @ Typesafe <http://typesafe.com/> > -- >>>>>>>>>> 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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