CODEWITHSUNDEEP
scalagroovyakkazeromq
Henry VIII
Henry VIII

Reputation: 157

AKKA: Communicating via Messaging Queue

We have a component written in Groovy ( let's call it a "G-Component" ) that needs to communicate with a component written in Scala / AKKA ( let's call it an "A-Component" ).

What fits our needs best is a messaging queue:

"G-COMPONENT" <==> in memory messaging queue <==> "A-COMPONENT"

For the "G-COMPONENT" life is simple:

queue.send( message )
message = queue.receive()

For the AKKA component it seems a bit more involved, since there is an Actor that needs to "handle"/"receive" messages, and be able to "send" messages back.

The problem is the "receive" part, as it now needs to go into a loop of its own to listen for messages from the queue. Which.. disables it as an AKKA Actor, since once it is in that loop, it can't receive any AKKA messages.

Would appreciate any help on the clean solution for this, without implementing an AKKA plugin of "that particular queue implementation" Actor mailbox.

Upvotes: 2

Views: 3884

Answers (3)

Michael Dillon
Michael Dillon

Reputation: 32392

AKKA is a library not a programming language.

Just write the zeromq message listener outside of an actor, and have it send incoming zeromq messages to AKKA actors. I've done this with AMQP using the Java AMQP client library and it works just fine.

If you want the ZeroMQ listener to be running in an event loop, then it is easy enough to write your own using the select poller http://api.zeromq.org/2-1:zmq-poll Have a look at the ConcurrentSocketActor source code in the AKKA zeromq module because that's what it uses. This would be a good model if you ever need to roll your own concurrent actor for some other type of network communication.

And this is the same problem that people have when they want to add a network accessible management interface to a non-network application in any language.

Upvotes: 0

Henry VIII
Henry VIII

Reputation: 157

converting a "question edit" to an answer

Found an interesting development going of not yet officially released AKKA API:

"Akka provides a ZeroMQ module which abstracts a ZeroMQ connection and therefore allows interaction between Akka actors to take place over ZeroMQ connections."

Seems that I can have an AKKA way to spawn a ZeroMQ listener:

val listener = actorOf(new Actor {
  def receive: Receive = {
    case message: ZMQMessage => ...
    case _ => ...
  }
}).start

val socket = ZMQ.newSocket(SocketParameters(context, SocketType.Sub, Some(listener)))
socket ! Connect("tcp://127.0.0.1:1234")
socket ! Subscribe(Seq())

confirmed by Viktor Klang (question comments) this is the way to go

Upvotes: 3

Andrew
Andrew

Reputation: 436

This may be obvious but Akka has excellent camel and amqp integration.

http://akka.io/docs/akka-modules/1.2/modules/camel.html http://akka.io/docs/akka-modules/1.2/modules/amqp.html

I am not sure what you mean by 'without implementing an AKKA plugin of "that particular queue implementation" Actor mailbox'. Does that mean you don't want to use these components?

Upvotes: 1

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