What you want to do is process all the events coming from the
PersistenceQuery stream and create a view that can be queried, for example:
transform all the events into normalized data and insert them into
ElasticSearch.
A quick example would look like the following (using EventStoreReadJournal):
val queries = PersistenceQuery(system).readJournalFor
[EventStoreReadJournal](EventStoreReadJournal.Identifier)
queries.allPersistenceIds()
.runForeach { persistenceId =>
queries.eventsByPersistenceId(persistenceId).map(_.event).runForEach(elasticSearchIndexer
! _)
}
Hope this helps.
On a side note, one of the things I'm struggling with instead is how to
process the event stream if I have a cluster of nodes on my read side
without having all the nodes processing all the events coming from the
events source, potentially I would like to have each node indexing a subset
of the events into my ElasticSearch database.
Does anyone have any guidance on how to achieve this?
The problem is that I have no way to chop the stream up in my read nodes
based on my cluster shards for example, the PersistentView played well with
cluster sharding, but what about PersistenceQuery?
On Sunday, November 8, 2015 at 5:36:57 PM UTC, Adam Dohnal wrote:
>
> Hello,
>
> recently I read through new akka-persistence-query-experimental module and
> would like to see some tutorials and examples to see how it can work.
> Documentation is really abstract for me. Unfortunately, I'm not able to
> find any activator templates nor tutorials.
>
> What I understand is how can I get a stream of events for my aggregate
> root. But how can I construct my read model. Should I subscribe to that
> event stream and for each event I should update ma read model and store it
> to read database? I think I am little confused.
>
> Can you guys share your experience with that module? Some blog posts,
> mini-projects on github etc... to show how can it be used to implement
> query side of CQRS? Thank you
>
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