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May 8, 2014 22:09
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Demonstration of Akka Cluster Singleton Communication Problem
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| package sample.cluster.simple | |
| import com.typesafe.config.ConfigFactory | |
| import akka.actor.ActorSystem | |
| import akka.actor.Props | |
| import akka.actor._ | |
| import akka.contrib.pattern.ClusterSingletonManager | |
| import akka.contrib.pattern.ClusterSingletonProxy | |
| class MyClusterActor extends Actor { | |
| def receive = { | |
| case msg => { | |
| println("MyClusterActor got *" + msg + "* from " + sender().path) | |
| sender() ! "Here's a response from MyClusterActor" | |
| } | |
| } | |
| } | |
| case class Start(actor: ActorRef) | |
| class MyRemoteActor extends Actor { | |
| def receive = { | |
| case Start(actor) => { | |
| println("MyRemoteActor got Start with " + actor.path) | |
| actor ! "Hello from RemoteActor" | |
| } | |
| case msg => { | |
| println("MyRemoteActor got *" + msg + "* from " + sender().path) | |
| } | |
| } | |
| } | |
| object RemoteSystem { | |
| val remoteConfig = ConfigFactory.parseString("akka.actor.provider=\"akka.remote.RemoteActorRefProvider\""). | |
| withFallback(ConfigFactory.parseString("akka.remote.enabled-transports=[\"akka.remote.netty.tcp\"]")). | |
| withFallback(ConfigFactory.parseString("akka.remote.netty.tcp.hostname=\"127.0.0.1\"")). | |
| withFallback(ConfigFactory.parseString("akka.remote.netty.tcp.port=2551")) | |
| val remoteSystem = ActorSystem("RemoteSystem", remoteConfig) | |
| val remoteActor = remoteSystem.actorOf(Props[MyRemoteActor], "myremoteactor") | |
| val clusterConfig = ConfigFactory.parseString("akka.actor.provider=\"akka.cluster.ClusterActorRefProvider\""). | |
| withFallback(ConfigFactory.parseString("akka.remote.enabled-transports=[\"akka.remote.netty.tcp\"]")). | |
| withFallback(ConfigFactory.parseString("akka.remote.netty.tcp.hostname=\"127.0.0.1\"")). | |
| withFallback(ConfigFactory.parseString("akka.cluster.seed-nodes=[\"akka.tcp://ClusterSystem@127.0.0.1:2553\"]")). | |
| withFallback(ConfigFactory.parseString("akka.remote.netty.tcp.port=2552")) | |
| val clusterSystem = ActorSystem("ClusterSystem", clusterConfig) | |
| val clusterActor = clusterSystem.actorOf(ClusterSingletonProxy.props( | |
| singletonPath = "/user/myclusteractor/active", | |
| role = None), | |
| name = "MyClusterActor") | |
| } | |
| object ClusterSystem { | |
| val clusterConfig = ConfigFactory.parseString("akka.actor.provider=\"akka.cluster.ClusterActorRefProvider\""). | |
| withFallback(ConfigFactory.parseString("akka.remote.enabled-transports=[\"akka.remote.netty.tcp\"]")). | |
| withFallback(ConfigFactory.parseString("akka.remote.netty.tcp.hostname=\"127.0.0.1\"")). | |
| withFallback(ConfigFactory.parseString("akka.cluster.seed-nodes=[\"akka.tcp://ClusterSystem@127.0.0.1:2553\"]")). | |
| withFallback(ConfigFactory.parseString("akka.remote.netty.tcp.port=2553")) | |
| val clusterSystem = ActorSystem("ClusterSystem", clusterConfig) | |
| clusterSystem.actorOf(ClusterSingletonManager.props(Props(classOf[MyClusterActor]), "active", | |
| PoisonPill, None), "myclusteractor") | |
| def setup() = println("Setting up ClusterSystem") | |
| } |
tip: scala supports:
parseString("""akka.remote.enabled-transports="akka.remote.netty.tcp"
akka.remote.netty.tcp.hostname="127.0.0.1"
""")
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For convenience, you can drop this file into
akka-samples/akka-sample-cluster-scala/src/main/scala/sample/cluster/simple/and do this:On VM #1:
So, now the cluster is up and running on port 2553, and the singleton (myclusteractor) is running on it.
Now, on VM #2:
Now, the cluster is set up on VM #2 on port 2552. It found the seed on 2553 and joined the cluster and found the singleton. VM #2 also has a separate system set up for remoting on port 2551.
Back on VM #1, we see it acknowledge the new node:
Now, back on VM #2, we send a message to the singleton:
back on VM #1, we see that the cluster actor receives the message. (We don't get a response, because we didn't send the message from an actor that can receive messages.)
Now, back on VM #2, we send a Start message to the remoteActor, passing it the proxy for the cluster singleton. The remoteActor will then send a message to the singleton, and should receive a message back when the singleton responds to
sender():On VM #1, we see that the singleton gets the message from remoteActor:
But, note that the address for the sender() is not correct. It should be RemoteSystem, not ClusterSystem.
In VM #2, we see that the attempt to respond back to remoteActor indeed fails: