On Mon, Oct 20, 2014 at 2:03 PM, Prakhyat Mallikarjun <prakhyat...@gmail.com > wrote:
> Hi Patrik, > > Thanks for your inputs. > > Views will be updated. Can we get a look on the design of how view will be > implemented in future? > There is nothing more than the famous Akka Persistence on the Query Side: The Conclusion <https://groups.google.com/forum/#!topic/akka-user/MNDc9cVG1To>. > Is there any possibility the current class akka.persistence.PersistentView > will be renamed or removed. I am asking from the perspective of migration. > That is possible. This is the reason why we always release new things as experimental. Sometimes things must be improved based on real world usage. > What will be the impact on migration from current persistent view > implementation to future changes in PersistentView? > Current functionality of PersistentView is rather limited and it should not be difficult to build something similar on top of the new thing. There will be a decent migration path, but I can't promise that we will provide anything that is source compatible. > > I understand the current PersistentView cannot aggregate events from > multiple PersistentActor. I am aware it will be supported in future version > of akka persistence. I am waiting to look at these changes :) > > But, I have query in current implementation of view, > 1. Correct me If I am wrong, view can be started with particular sequence > number. The sequence number should be passed as a constructor parameter to > view. > 2. My fundamental problem is how to get hold of the last sequence number > read by a view before it was dead? > You must be prepared to process the same event again, i.e. PersistentView has at-least once semantics. /Patrik > > -Prakhyat M M > > On Monday, 20 October 2014 14:15:01 UTC+5:30, Patrik Nordwall wrote: >> >> Hi Prakhyat, >> >> I can't comment on ahjohannessen proposal, but in general it is difficult >> to create a view that aggregates the event streams of many persistent actor >> instances, and it is also difficult to create a persistent view for each >> persistent actor when you don't know the identifiers up front. >> >> You can store the identifers in another persistent actor, and let that >> actor be responsible for creating the views. This is not trivial, and one >> of the reasons why we want to improve the persistent views. The core team >> is swamped with other work so it will take a few more months until we can >> start working on the improved persistent views. >> >> Cluster sharding for the views will only work if you send messages to >> these views, because cluster sharding entry actors are only activated when >> messages are sent to them. >> >> Regards, >> Patrik >> >> On Wed, Oct 15, 2014 at 2:37 PM, Prakhyat Mallikarjun <prakh...@gmail.com >> > wrote: >> >>> Team, >>> >>> I am eagerly looking for the answer to this query. Any updates would be >>> appreciated and helpful. >>> >>> -Prakhyat M M >>> >>> >>> On Sunday, 12 October 2014 20:59:10 UTC+5:30, Prakhyat Mallikarjun wrote: >>>> >>>> Hi Ahjohannessen, >>>> >>>> I understand your point. And I thoroughly agree your inputs. >>>> >>>> But the point I want is make is as below.... >>>> Correct me if I am wrong, the view will always be in lag compared to >>>> the persistent actor. It will always pull the events persisted by >>>> persistent actor. The last seen sequence number in persistent actor might >>>> be different from last pulled sequence number in persistent view. >>>> >>>> Just to take an example consider PersistentActor persist events in >>>> order 1,2,3,4,5,6. The view pulls persisted event from journal in order >>>> 1,2,3,4,5,6 at lag duration of 2-5 secs. >>>> >>>> Consider persistent actor persisted 1,2,3,4,5,6. View pull's event >>>> 1,2,3,4. But while handling event 4, exception is thrown. The fault >>>> tolerance case which we are discussing here is view should be >>>> recreated/started from sequence 4 followed by 5,6. >>>> >>>> Correct me if my understanding is wrong. >>>> >>>> -Prakhyat M M >>>> >>>> On Sunday, 12 October 2014 19:35:58 UTC+5:30, ahjohannessen wrote: >>>>> >>>>> Prakhyat, it is really simple. Just wrap the message in case class >>>>> ViewRead(msg: Any, sequenceNr: Long, persistenceId: String) and maintain a >>>>> pointer of last seen sequenceNr per persistent actor, i.e. persistenceId. >>>>> Then you can start "CatchUp" from that. >>>> >>>> -- >>> >>>>>>>>>> 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. >>> To post to this group, send email to akka...@googlegroups.com. >>> Visit this group at http://groups.google.com/group/akka-user. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> >> >> -- >> >> Patrik Nordwall >> Typesafe <http://typesafe.com/> - Reactive apps on the JVM >> Twitter: @patriknw >> >> -- > >>>>>>>>>> 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 http://groups.google.com/group/akka-user. > For more options, visit https://groups.google.com/d/optout. > -- Patrik Nordwall Typesafe <http://typesafe.com/> - Reactive apps on the JVM Twitter: @patriknw -- >>>>>>>>>> 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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