I'm not sure I understand. You want to read the old data if the persistent
actor doesn't have any events of its own?

You can check the state when you get RecoveryCompleted. You can also count
the events/snapshot in receiveRecover and act on that when
RecoveryCompleted.

/Patrik

fre 14 okt. 2016 kl. 22:11 skrev Jakub Liska <liska.ja...@gmail.com>:

> Hey,
>
> what is the best practice to do in this hypothetical scenario :
> 1) Say you have a time series pipeline that started at 2014 and created
> persistent state on S3 and other DB systems
> 2) You can introspect these storages and know what partitions already
> exists in all of them
> 3) The persistent actor's job would be scheduling tasks for newly added
> partitions (next minute/hour/day, etc.)
> 3) Now at 2016 you deploy a persistent Actor that will hold state about
> completness (existing partitions) of these storages and keep up with their
> progress
>
> The way I see it, when this persistent Actor boots up, it will have 2
> choices :
> a) either it starts for the very first time, it will have to replay all
> DomainEvents for all historical partitions from 2014 to itself to
> initialize it's state to the current view of the world in 2016
> b) or it restarts or crashes and its state is replayed from the journal
> implicitly
>
> Now I cannot find any reference of how this should be done. The only
> solution that comes to mind is to use persistence-query and obtaining
> Journal :
>
>    readJournal.currentPersistenceIds()
>    readJournal.eventsByPersistenceId("user-us-1337")
>    1.
>    And if the result is empty, then it will reconstructs the history.
>
> Is this a way to go?
>
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