How to create a callable source using akka streams

Question

We have the following architecture

SQS(source) -> SQS Pollers -> Our business logic -> Sink which deletes messages from SQS.

This is an akka stream (our business logic has multiple stages).

Now we want to extend this architecture by adding an HTTP server (not Akka HTTP).

Now our service also has a path

HTTP Server -> Our business logic -> Sink which completes a future indicating the HTTP response is complete.

Now whenever an HTTP request comes, I need a mechanism to call the stream.

Right now the SQS source is essentially a long running thread that calls the service and pushes the message to the rest of the akka stream.

I am essentially trying to create a "callable" akka source, such that the source is triggered only when we get a request.

I was looking https://doc.akka.io/docs/akka/2.5/stream/operators/Source/queue.html as a potential solution here, but that only returns a handle to call after the entire runnable graph has been materialized, so it makes it a bit ugly to merge the SQS poller source and the HTTP callable source.

Answer 1

I think indeed Source.queue would be the way to go here, materialize the stream once and offer elements to the queue both from your HTTP server endpoint and from your SQS poller. Is there any particular reason this would be ugly to share?