Akka Persistence: Issue starting PersistentActor: java.lang.IllegalArgumentException: Default journal plugin is not configured, see 'reference.conf'

Question

I am trying to work with PersistentActor in Akka.

I tried the basic example provided in the Akka documentation at https://doc.akka.io/docs/akka/current/persistence.html.

I am getting the following error at the starting of the actor:

Caused by: java.lang.IllegalArgumentException: Default journal plugin is not configured, see 'reference.conf' at akka.persistence.Persistence$.verifyPluginConfigIsDefined(Persistence.scala:193) at akka.persistence.Persistence.defaultJournalPluginId$lzycompute(Persistence.scala:228) at akka.persistence.Persistence.defaultJournalPluginId(Persistence.scala:226) at akka.persistence.Persistence.journalConfigFor(Persistence.scala:336) at akka.persistence.Eventsourced.$init$(Eventsourced.scala:97) at akka.persistence.AbstractPersistentActor.(PersistentActor.scala:455) at org.spituk.learning.akka.samples.ExamplePersistentActor.(ExamplePersistentActor.java:72)

The code I tried is like:

import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.persistence.AbstractPersistentActor;
import akka.persistence.SnapshotOffer;

import java.io.IOException;
import java.io.Serializable;
import java.util.ArrayList;

class Cmd implements Serializable {

    private static final long serialVersionUID = 1L;
    private final String data;

    public Cmd(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }
}

class Evt implements Serializable {

    private static final long serialVersionUID = 1L;
    private final String data;

    public Evt(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }
}

class ExampleState implements Serializable {

    private static final long serialVersionUID = 1L;
    private final ArrayList<String> events;

    public ExampleState() {
        this(new ArrayList<>());
    }

    public ExampleState(ArrayList<String> events) {
        this.events = events;
    }

    public ExampleState copy() {
        return new ExampleState(new ArrayList<>(events));
    }

    public void update(Evt evt) {
        events.add(evt.getData());
    }

    public int size() {
        return events.size();
    }

    @Override
    public String toString() {
        return events.toString();
    }
}

public class ExamplePersistentActor extends AbstractPersistentActor {

    private int snapShotInterval = 1000;
    private ExampleState state = new ExampleState();

    public static Props props() {
        return Props.create(ExamplePersistentActor.class);
    }

    public int getNumEvents() {
        return state.size();
    }

    @Override
    public String persistenceId() {
        return "sample-id-1";
    }

    @Override
    public Receive createReceiveRecover() {
        return receiveBuilder()
                .match(Evt.class, state::update)
                .match(SnapshotOffer.class, ss -> state = (ExampleState) ss.snapshot())
                .build();
    }

    @Override
    public Receive createReceive() {
        return receiveBuilder()
                .match(
                        Cmd.class,
                        c -> {
                            final String data = c.getData();
                            final Evt evt = new Evt(data + "-" + getNumEvents());
                            System.out.println("Cmd received::" + c);
                            persist(
                                    evt,
                                    (Evt e) -> {
                                        state.update(e);
                                        getContext().getSystem().getEventStream().publish(e);
                                        if (lastSequenceNr() % snapShotInterval == 0 && lastSequenceNr() != 0)
                                            // IMPORTANT: create a copy of snapshot because ExampleState is mutable
                                            saveSnapshot(state.copy());
                                    });
                        })
                .matchEquals("print", s -> System.out.println(state))
                .build();
    }

    public static void main(String[] args) throws IOException {
        ActorSystem persistentSystem = ActorSystem.create("persistent-system");
        ActorRef persistentSystemActor = persistentSystem.actorOf(ExamplePersistentActor.props());
        persistentSystemActor.tell(new Cmd("Hello"), ActorRef.noSender());
        System.in.read();
        persistentSystem.terminate();
    }
}

I have not defined any configurations for the persistence intend to use the built-in default plugins. Can someone please help me with this?

Answer 1

I had to add the following to the application.conf file:

akka.persistence.journal.plugin = "akka.persistence.journal.leveldb"
akka.persistence.snapshot-store.plugin = "akka.persistence.snapshot-store.local"

akka.persistence.journal.leveldb.dir = "target/example/journal"
akka.persistence.snapshot-store.local.dir = "target/example/snapshots"

# DO NOT USE THIS IN PRODUCTION !!!
akka.persistence.journal.leveldb.native = false