Thanks. So I guess you're basically using a persistent actor as a durable queue, in place of something like a Kafka topic, and a single message on the queue can include ids of multiple aggregates.
On Sat, May 9, 2015 at 10:51 AM, Olger Warnier <ol...@spectare.nl> wrote: > Hi Richard, > > I use the akka cluster sharding mechanism to start instances of a > PersistentActor. > This actor stands for a single instance of an AggregateRoot (DDD concept) > This specific instance contains the logic required to run. > > For instance this can be a UserAccount instance of a user called ‘foo’ and > changing the password will be handled by UserAccount and applied to this > specific instance as the user ‘foo’ wants to change its password. > Another user called ‘bar’ will have its own instance of this > PersistentActor running somewhere in the cluster. > > Let’s assume that the usernames are the unique identifiers for these > persistent actors. (persistenceIds) > Replaying to the state for a specific instance (for instance ‘foo’) is > done by creating a view with the persistenceId ‘foo’) > > As the PersistenceActors make use of the persistenceId that is the ‘key’ > for that specific instance, it is hard to tell what the persistenceId for > your view needs to be. > Somebody registers the user ‘noname’ -> a persistent actor is created via > cluster sharding with the persistenceID ‘noname’. as that is all async in > nature, you need a way to know that this persistent actor is created (or > received a change for that matter, as actors may be put to sleep) > > So, I have a singleton persistent actor that keeps track of changes with a > ‘known’ persistenceId. When change happens to ‘foo’, ‘bar’ and ‘noname’, > they will notify the PersistentActor with an id as > ‘user-account-change-tracker’ that will write something like > UserAccountChanged(‘noname’) > A view that listens to ‘user-account-change-tracker’ will thereafter > create the views for the specific user (for this matter ‘noname’) and > replay / restore the state for that view as required. (mostly elasticsearch > indexes that are used for the query side of my application) > > As the other approaches, this has advantages and drawbacks. > 1) the use of cluster sharding is something you may not need (but if you > do, persistence and cluster sharding work well together) > 2) the event store is filled with ‘change’ events in order to trigger the > real views to materialise > 3) it is not dependent on a specific event store backend and therefore > easier to include in your unit tests using the components available with > akka-persistence > > With the other options, choices enough. Apply them as you require. > > Kind regards, > > Olger > > > > > > > On Fri, May 8, 2015 at 10:58 PM, Richard Rodseth <rrods...@gmail.com> > wrote: > >> Hi Olger >> >> Could you please elaborate a bit on your appoach? I'm not sure I follow. >> >> Thanks. >> >> On Fri, May 8, 2015 at 4:17 AM, Olger Warnier <ol...@spectare.nl> wrote: >> >>> Hi Alejandro, >>> >>> You have a number of options >>> >>> - when you have a single persistence Id, write a view for that >>> - when you want to aggregate events of several persistence ids, you can >>> do so via the event store (approach of Martin (with Kafka) and Greg (event >>> store) ) >>> Or you can aggregate the changes to a message queue and read that >>> Or you can aggregate via another persistent actor that publishes the >>> fact that something has changed for a specific other persistence id and >>> start a view for that id (my approach) >>> >>> And there may be other ways to solve this of course. >>> >>> Kind regards, >>> >>> Olger >>> >>> >>> >>> On Fri, May 8, 2015 at 1:07 PM, Alejandro López <ale64...@gmail.com> >>> wrote: >>> >>>> Right now, what would be the best alternative in order to create >>>> projections, allowing views to subscribe to arbitrary events as described >>>> by Roland above? (or at least a coarse approximation) >>>> >>>> -- >>>> >>>>>>>>>> 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/MNDc9cVG1To/unsubscribe. >>>> To unsubscribe from this group and all its topics, 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. >>>> >>> >>> -- >>> >>>>>>>>>> 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. >>> >> >> -- >> >>>>>>>>>> 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/MNDc9cVG1To/unsubscribe. >> To unsubscribe from this group and all its topics, 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. >> > > -- > >>>>>>>>>> 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. > -- >>>>>>>>>> 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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