Akka 2.1 minimal remote actor example - scala

Question

EDIT Notice, I needed to make the reverse changes of this https://github.com/akka/akka/commit/ce014ece3568938b2036c4ccfd21b92faba69607#L13L6 to make the accepted answer work with AKKA 2.1 which is the stable distribution found on akkas homepage!
I have read all the tutorials I could find on AKKA, but nothing I found works "out of box".
Using eclipse, I want to create 2 programs.
Program1:
starts actor "joe" and somehow makes it available on 127.0.0.1:some_port
Program2:
gets a reference to actor "joe" at 127.0.0.1:some_port. Sends a hello message to "joe".
Program 1 should print something when the message is received. I want to run this example in eclipse using AKKA 2.1. Can someone list 2 programs, (program1 and program2) together with a working application.conf file that does this and nothing else?
edit>
let me show you what I got so far:
actor
case class Greeting(who: String) extends Serializable
class GreetingActor extends Actor with ActorLogging {
def receive = {
case Greeting(who) ⇒ println("Hello " + who);log.info("Hello " + who)
}
}
Program1:
package test
import akka.actor.ActorSystem
object Machine1 {
def main(args: Array[String]): Unit = {
val system = ActorSystem("MySystem")
}
}
Program2
package test
import akka.actor.ActorSystem
import akka.actor.Props
import akka.actor.actorRef2Scala
object Machine2 {
def main(args: Array[String]): Unit = {
val system = ActorSystem("MySystem")
val greeter = system.actorOf(Props[GreetingActor], name = "greeter")
greeter ! Greeting("Felix")
}
}
application.conf
akka {
actor {
deployment {
/greeter {
remote = "akka://MySystem#127.0.0.1:2553"
}
}
}
}
However, this program works when I start only Program2 and it outputs:
Hello Felix
[INFO] [02/18/2013 12:27:29.999] [MySystem-akka.actor.default-dispatcher-2] [akka://MySystem/user/greeter] Hello Felix
It seems that it is not picking up my application.conf. I tried placing it both in the ./src/ and ./ folder of my eclipse project. No difference. Also, I know this is really demote deployment, but I need just a hello world program to work using AKKA. I spent so much time on this without getting a simple working application.

Answer 1

Update for Akka 2.2.3
A minimal remote application can be created as follows:
Create 2 Projects in Eclipse: Client and Server
Server:
The code for the server is
package server
import akka.actor.Actor
import akka.actor.ActorLogging
import akka.actor.ActorSystem
import akka.actor.Props
class Joe extends Actor {
def receive = {
case msg: String => println("joe received " + msg + " from " + sender)
case _ => println("Received unknown msg ")
}
}
object Server extends App {
val system = ActorSystem("GreetingSystem")
val joe = system.actorOf(Props[Joe], name = "joe")
println(joe.path)
joe ! "local msg!"
println("Server ready")
}
The applincation.conf for the server is
akka {
loglevel = "DEBUG"
actor {
provider = "akka.remote.RemoteActorRefProvider"
}
remote {
enabled-transports = ["akka.remote.netty.tcp"]
netty.tcp {
hostname = "127.0.0.1"
port = 2552
}
log-sent-messages = on
log-received-messages = on
}
}
Client:
The Client-code is
package client
import akka.actor._
import akka.actor.ActorDSL._
object Greet_Sender extends App {
println("STARTING")
implicit val system = ActorSystem("GreetingSystem-1")
val joe = system.actorSelection("akka.tcp://GreetingSystem#127.0.0.1:2552/user/joe")
println("That 's Joe:" + joe)
val a = actor(new Act {
whenStarting { joe ! "Hello Joe from remote" }
})
joe ! "Hello"
println("Client has sent Hello to joe")
}
The client application.conf is:
akka {
#log-config-on-start = on
stdout-loglevel = "DEBUG"
loglevel = "DEBUG"
actor {
provider = "akka.remote.RemoteActorRefProvider"
}
remote {
enabled-transports = ["akka.remote.netty.tcp"]
log-sent-messages = on
log-received-messages = on
netty.tcp {
hostname = "127.0.0.1"
port = 0
}
}
}
Configurations have to be placed in two files called application.conf, both within the bin directory of the two projects.

Answer 2

As korefn mentioned, the remote documentation explains it's workings in detail. It also links to an example application. That example should give you everything you need to get started.
Edit
To get the sample application running perform the following steps:
Clone from GitHub
eecolor#BLACK:~/GihHub$ git clone https://github.com/akka/akka.git
Go into the akka directory and run sbt
eecolor#BLACK:~/GihHub/akka$ sbt
Switch to the akka-sample-project
akka > project akka-sample-remote
Call run on the project and select the CalcApp
Multiple main classes detected, select one to run:
[1] sample.remote.calculator.java.JCreationApp
[2] sample.remote.calculator.LookupApp
[3] sample.remote.calculator.CalcApp
[4] sample.remote.calculator.java.JLookupApp
[5] sample.remote.calculator.CreationApp
[6] sample.remote.calculator.java.JCalcApp
Enter number: 3
[info] Running sample.remote.calculator.CalcApp
[INFO] [02/19/2013 19:22:09.055] [run-main] [Remoting] Starting remoting
[INFO] [02/19/2013 19:22:09.230] [run-main] [Remoting] Remoting started; listening on addresses :[akka.tcp://CalculatorApplication#127.0.0.1:2552]
Started Calculator Application - waiting for messages
Switch to another console and repeat the first few steps
eecolor#BLACK:~/GihHub/akka$ sbt
akka > project akka-sample-remote
Call run and select the LookupApp
akka-sample-remote > run
Multiple main classes detected, select one to run:
[1] sample.remote.calculator.java.JCreationApp
[2] sample.remote.calculator.LookupApp
[3] sample.remote.calculator.CalcApp
[4] sample.remote.calculator.java.JLookupApp
[5] sample.remote.calculator.CreationApp
[6] sample.remote.calculator.java.JCalcApp
Enter number: 2
[info] Running sample.remote.calculator.LookupApp
[INFO] [02/19/2013 19:23:39.358] [run-main] [Remoting] Starting remoting
[INFO] [02/19/2013 19:23:39.564] [run-main] [Remoting] Remoting started; listening on addresses :[akka.tcp://LookupApplication#127.0.0.1:2553]
Started Lookup Application
Sub result: 14 - 16 = -2
Sub result: 13 - 22 = -9
Add result: 56 + 93 = 149
Add result: 18 + 19 = 37
Switch back to the other console and you should see something like this:
Calculating 14 - 16
Calculating 13 - 22
Calculating 56 + 93
Calculating 18 + 19

Answer 3

Well, in your example, the Client code never references the config file and it won't work.

Answer 4

akka by default will use the application.conf file - so it does not need to be explicitly selected.
if one does want to then the code would be (taking the code above as an exmaple):
val configFile = getClass.getClassLoader.getResource("akka_local_application.conf").getFile
val config = ConfigFactory.parseFile(new File(configFile))
val system = ActorSystem("GreetingSystem",config)
val joe = system.actorOf(Props[Joe], name = "joe")