pekko/akka-docs/rst/java/code/jdocs/cluster/TransformationFrontend.java

package jdocs.cluster;

import static jdocs.cluster.TransformationMessages.BACKEND_REGISTRATION;

import java.util.ArrayList;
import java.util.List;

import jdocs.cluster.TransformationMessages.JobFailed;
import jdocs.cluster.TransformationMessages.TransformationJob;
import akka.actor.ActorRef;
import akka.actor.Terminated;
import akka.actor.AbstractActor;

//#frontend
public class TransformationFrontend extends AbstractActor {

  List<ActorRef> backends = new ArrayList<ActorRef>();
  int jobCounter = 0;

  @Override
  public Receive createReceive() {
    return receiveBuilder()
      .match(TransformationJob.class, job -> backends.isEmpty(), job -> {
        getSender().tell(
          new JobFailed("Service unavailable, try again later", job),
            getSender());
      })
      .match(TransformationJob.class, job -> {
        jobCounter++;
        backends.get(jobCounter % backends.size())
          .forward(job, getContext());
      })
      .matchEquals(BACKEND_REGISTRATION, x -> {
        getContext().watch(getSender());
        backends.add(getSender());
      })
      .match(Terminated.class, terminated -> {
        backends.remove(terminated.getActor());
      })
      .build();
  }

}
//#frontend