On 19.08.14 13:40, Patrik Nordwall wrote:
On Tue, Aug 19, 2014 at 1:35 PM, Martin Krasser
<[email protected] <mailto:[email protected]>> wrote:
On 19.08.14 13:00, Roland Kuhn wrote:
19 aug 2014 kl. 11:28 skrev Ashley Aitken <[email protected]
<mailto:[email protected]>>:
On Tuesday, 19 August 2014 16:53:46 UTC+8, Martin Krasser wrote:
journal -> akka actor(s) -> read model datastore
when I can do this much more efficiently via
journal -> spark -> read model datastore
directly, for example
I am confused, are you suggesting that spark is talking to the
journal data store directly, without any involvement of Akka /
Akka Persistence? If so, it sounds like a great solution but
why would that require an extension to the Akka Persistence
design/API?
Well, another comment is that spark uses Akka actors in its
implementation, so I don’t see why it would magically be “much
more efficient”. I think we are mixing up two concerns here, will
reply later when I can type properly again.
This is a misunderstanding. As mentioned in my previous message,
scaling reads through a single journal actor doesn't work, it's
not about that I see a general performance issue with Akka actors.
I think the integration "akka persistence -> kafka -> spark ->
whatever" looks great, but not everybody has that infrastructure, and
therefore we provide PersistentView as a simple way to replicate
events to the read side, and then a de-normalized representation can
be stored in whatever makes sense for the queries.
Of course, that should be possible too, and as I already said, backend
store providers can choose to use the very same backend for both
plugins. There is absolutely no need that applications must use Spark as
part of their infrastructure infrastructure. But if it is needed in
large-scale applications, a seconds plugin API for on the read side
would make things much more flexible. For users, who just want to have a
single backend store, they just have to configure one additional line
(plugin) in their application conf.
Martin, what do you suggest? Removing PersistentView altogether?
No, not at all, with an additional plugin, PersistentViews should have
the option to read transformed/joined/... streams from a backend store
that is optimized for that.
/Patrik
Regards,
Roland
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