Patrik, Thanks a lot. Your inputs would help us a lot.
And for "There is nothing more than the famous Akka Persistence on the Query Side: The Conclusion <https://groups.google.com/forum/#!topic/akka-user/MNDc9cVG1To>." there is no doubt...its the most interesting post with great heads. I have looked at it many times. We are using views and any changes to it will impact our code. So want to be prepared. That's the reason I wanted to look at design of future views. So that few of the changes in our code i will do accommodation now itself. -Prakhyat M M On Monday, 20 October 2014 21:52:28 UTC+5:30, Patrik Nordwall wrote: > > > > On Mon, Oct 20, 2014 at 2:03 PM, Prakhyat Mallikarjun <[email protected] > <javascript:>> 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 < >>> [email protected]> 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 [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. >>>> >>> >>> >>> >>> -- >>> >>> 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 [email protected] <javascript:>. >> To post to this group, send email to [email protected] >> <javascript:>. >> 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 [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.
