Unable to resolve akka.pattern.AskTimeoutException: Ask timed out - akka

Question

I am trying to replace the default LevelDB in OpenDaylight with Apache Ignite which i am unable to do after making changes to the akka.conf file and deploying the akka-persistence-ignite jar that i found here. https://github.com/Romeh/akka-persistance-ignite
I am facing an issue in the following line of the source code (AbstractDataStoreClientActor class) where it throws a Runtime Exception.
private static final Function1<ActorRef, ?> GET_CLIENT_FACTORY = ExplicitAsk.toScala(GetClientRequest::new);
#SuppressWarnings("checkstyle:IllegalCatch")
public static DataStoreClient getDistributedDataStoreClient(#Nonnull final ActorRef actor,
final long timeout, final TimeUnit unit) {
return (DataStoreClient) Await.result(ExplicitAsk.ask(actor, GET_CLIENT_FACTORY,
Timeout.apply(timeout, unit)), Duration.Inf());
which gives the following error
akka.pattern.AskTimeoutException: Ask timed out on [Actor[akka://opendaylight-cluster-data/user/$a#-809157907]] after [30000 ms]. Sender[null] sent message of type "org.opendaylight.controller.cluster.databroker.actors.dds.GetClientRequest".
My question is how can i know the behavior of the actor to which the above message is sent? Is there any way to check if the actor has been created properly? What could be the reason for which the Ask method is going to timeout?
EDIT:::: error stack trace from karaf.log
2018-07-12T11:27:01,755 | ERROR | opendaylight-cluster-data-akka.actor.default-dispatcher-18 | DistributedDataStoreClientActor | 90 - com.typesafe.akka.slf4j - 2.5.11 | Persistence failure when replaying events for persistenceId [member-1-frontend-datastore-config]. Last known sequence number [0]
java.lang.NullPointerException: null
at akka.japi.Util$.option(JavaAPI.scala:271) ~[84:com.typesafe.akka.actor:2.5.11]
at akka.persistence.snapshot.japi.SnapshotStore.$anonfun$loadAsync$1(SnapshotStore.scala:20) ~[87:com.typesafe.akka.persistence:2.5.11]
at scala.util.Success.$anonfun$map$1(Try.scala:251) ~[323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at scala.util.Success.map(Try.scala:209) ~[323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at scala.concurrent.Future.$anonfun$map$1(Future.scala:288) ~[323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:29) ~[323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:29) ~[323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60) ~[323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:55) ~[84:com.typesafe.akka.actor:2.5.11]
at akka.dispatch.BatchingExecutor$BlockableBatch.$anonfun$run$1(BatchingExecutor.scala:91) ~[84:com.typesafe.akka.actor:2.5.11]
at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12) [323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:81) [323:org.scala-lang.scala-library:2.12.5.v20180316-130912-VFINAL-30a1428]
at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:91) [84:com.typesafe.akka.actor:2.5.11]
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40) [84:com.typesafe.akka.actor:2.5.11]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:?]
at java.lang.Thread.run(Thread.java:748) [?:?]

Answer 1

The issue is not with DistributedDatastoreClientActor - it is a side-effect of an issue with the persistence backend - see my previous comment. Notice that the error stack trace contains an NPE emanating from akka.persistence.snapshot.japi.SnapshotStore which indicates the backing SnapshotStore unexpectedly returned null from loadAsync. This points to the ignite plugin.