Returning a String from a REST Call Using Akka/Play-mini

Question

Akka seems like a dream come true. Sadly, like so much other software, the documentation and examples are lacking in some major ways. Since the whole point of the thing is to provide non-blocking, parallel io, why would they provide a hello world that just returns a string. Here's a nutty idea: have an agent for each word, translate it into another language by calling something on the web, then returning the results.

I went around in circles today reading documentation about Futures and Promises. One working example would have obviated the whole thing.

I have done a lot of concurrent programming with Future in the java concurrency package. For some reason, the Akka stuff just seems way too complicated. I am doing something very close to what I described above: getting a request and having several agents fulfill it over the web. I took the original generated project that has the Master and the Listener as the starting point and it works fine, I just can't figure out a simple way to return the aggregated results. I have a play-mini method that is getting called. From there, I am calling a method on a class that sends the messages to the agents and when they are done running, their results get aggregated and the Listener gets called. How do I compose a Future out of that? All the documentation says don't block but we are having to return from a REST request.

Does anyone know of such an example? Super simple. Thanks.

Answer 1

I ended up doing composed Futures. Works pretty well. When you create a sequence, you still have to call Await, but the parallel execution still returned in ⅓ of a second so I'm happy.

As to getting Actors to handle a REST request, I thought about passing it a Future and then waiting on that? Might play around with some of those possibilities, but what I have now works.

The other question this experience raised for me is how to implement Ask in an Actor. Not covered in the docs and given the name, searching for Akka and ask is pretty much useless.

Here's a suggestion: each of these mechanisms should be shown in sequence diagrams. How hard would that be to do??

Still really excited about Akka. It's awesome to finally be able to do Actor-based programming.