Hi,
I wanted as well to use ActorPublisher/ActorSubcriber pair. My use case was
related to dynamically scaled number of wokers on a transforming task with
a possible worker failure, restart and redo (based on Work Pulling pattern
by Derek Wyatt
on
http://letitcrash.com/post/29044669086/balancing-workload-across-nodes-with-akka-2
)
I wanted to use streams for all other processing but this particular stage
needs to be dynamically scaled so I cannot use cookbook pattern "Balancing
jobs to a fixed pool of workers" and I am not yet sure if i can use actor
ask pattern from "Globally limiting the rate of a set of streams" example
to achieve desired result.
Independently of my particular problem I think the question could be
restated what is the best practice in interfacing a flow transformer in
akka streams with other parts of system which use actors. To be more exact
is it possible for a Flow transformer (Sink and Source works) to process
actor messages from external world which goes beyond actor ask pattern from
Limiter example and be able to receive and process external actor messages
in a thread safe way. I think it implies that the underlying actor must be
the same instance for stream management and custom processing as it is for
an ActorSubcriber or ActorPublisher.
I imagine the api would extend the existing PropsSource and PropsSink and
add a PropsFlow
trait ActorFlow[In, Out] extends ActorPublisher[Out] with ActorSubscriber {
.. }
class MyActorFlow extends ActorFlow[In, Out] { ... }
val props = Props(classOf[MyActorFlow])
val flowActor = PropsFlow[In, Out](props)
val source = ...
val sink = ....
val flowGraph = FlowGraph { implicit builder =>
source ~> flowActor ~> sink
}
I think all pieces are already available with ActorPublisher and
ActorSubscriber infrastructure and the missing part is some API code to
support ActorFlow in my example.
Best regards,
Piotr Buszka
On Friday, 26 December 2014 02:51:19 UTC+1, Konrad Malawski wrote:
>
> Hi Mark,
> would you mind explaining what exact use case you’re trying to cover?
> Instead of dropping down to reactive streams interfaces (publisher /
> subscriber) which are *very low-level*,
> instead you could perhaps stick with our much simpler to use custom Stages.
> Here’s the docs on implementing custom stages:
> http://doc.akka.io/docs/akka-stream-and-http-experimental/1.0-M2/scala/stream-customize.html
>
> And there are also plenty examples in the stream cookbook:
> http://doc.akka.io/docs/akka-stream-and-http-experimental/1.0-M2/scala/stream-cookbook.html
> which could be useful when implementing your custom processing stages.
>
> Hope this helps, happy hakking!
>
> --
> Konrad 'ktoso' Malawski
> hAkker @ typesafe
> http://akka.io
>
> On 25 December 2014 at 14:13:32, Mark van Buskirk (markvan...@gmail.com
> <javascript:>) wrote:
> Id love to see an example of two actors that are both publisher and
> subscriber connected. I've been trying to get that going and have been
> having a bunch of trouble getting it working.
>
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