How to attach multiple actors as sources to an Akka stream?

Question

I am trying to build and run an akka stream flow (in Java DSL) with 2 actors as sources, then a merge junction and then 1 sink:

    Source<Integer, ActorRef> src1 = Source.actorRef(100, OverflowStrategy.backpressure());
    Source<Integer, ActorRef> src2 = Source.actorRef(100, OverflowStrategy.backpressure());
    Sink<Integer, BoxedUnit> sink = Flow.of(Integer.class).to(Sink.foreach(System.out::println));

    RunnableFlow<BoxedUnit> closed = FlowGraph.factory().closed(sink, (b, out) -> {
        UniformFanInShape<Integer, Integer> merge = b.graph(Merge.<Integer>create(2));
        b.from(src1).via(merge).to(out);
        b.from(src2).to(merge);
    });

    closed.run(mat);

My question is how do I obtain ActorRef references to the source actors in order to send them messages? In case of 1 actor, I wouldn't be using graph builder, and then the .run() or runWith() method would return the ActorRef object. But what to do in case of many source actors? Is it even possible to materialize such a flow?

You need to pass the elements for which you need to access the materialized value to `closed` and then provide a function which combines the materialized values. Something like this: `closed(src1, src2, (actorRef1, actorRef2) -> SomethingContainingBothActorRefs, (b, s1, s2) -> ...)` — jrudolph, May 07 '15 at 09:07

score 6 · Answer 1 · edited Jul 26 '16 at 21:07

Answering my own question in case someone needs it.

Using jrudolph's advice, I was able to use actors like this (in actual code I did something nicer than a list of 2 ActorRefs):

    Source<Integer, ActorRef> src1 = Source.actorRef(100, OverflowStrategy.fail());
    Source<Integer, ActorRef> src2 = Source.actorRef(100, OverflowStrategy.fail());
    Sink<Integer, BoxedUnit> sink = Flow.of(Integer.class).to(Sink.foreach(System.out::println));

    RunnableFlow<List<ActorRef>> closed = FlowGraph.factory().closed(src1, src2, (a1, a2) -> Arrays.asList(a1, a2), (b, s1, s2) -> {
        UniformFanInShape<Integer, Integer> merge = b.graph(Merge.<Integer>create(2));
        b.from(s1).via(merge).to(sink);
        b.from(s2).to(merge);
    });

    List<ActorRef> stream = closed.run(mat);
    ActorRef a1 = stream.get(0);
    ActorRef a2 = stream.get(1);

How to attach multiple actors as sources to an Akka stream?

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