Spark difference between maven Artifacts spark-core_2.10 and spark-core_2.11

Question

Does anyone know the difference between the two spark core artifacts? Both support Spark up to version 1.5.1. However, I alawys end up with the same error when using spark-core_2.11 in my Java application and trying to connect to the standalone cluster(Spark-1.5.1) with the spark url (spark://masterIP:Port)

WARN ReliableDeliverySupervisor: Association with remote system [akka.tcp://[email protected]:7077] has failed, address is now gated for [5000] ms. Reason: [Disassociated] 
ERROR SparkUncaughtExceptionHandler: Uncaught exception in thread Thread[appclient-registration-retry-thread,5,main]

The Master also logs a compability problem in its logs:

ERROR Remoting: org.apache.spark.deploy.DeployMessages$RegisterApplication; local class incompatible: stream classdesc serialVersionUID = 352674063933172066, local class serialVersionUID = -5495080032843259921
java.io.InvalidClassException: org.apache.spark.deploy.DeployMessages$RegisterApplication; local class incompatible: stream classdesc serialVersionUID = 352674063933172066, local class serialVersionUID = -5495080032843259921
    at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:621)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1623)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1518)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1774)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
    at akka.serialization.JavaSerializer$$anonfun$1.apply(Serializer.scala:136)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:57)
    at akka.serialization.JavaSerializer.fromBinary(Serializer.scala:136)
    at akka.serialization.Serialization$$anonfun$deserialize$1.apply(Serialization.scala:104)
    at scala.util.Try$.apply(Try.scala:161)
    at akka.serialization.Serialization.deserialize(Serialization.scala:98)
    at akka.remote.serialization.MessageContainerSerializer.fromBinary(MessageContainerSerializer.scala:63)
    at akka.serialization.Serialization$$anonfun$deserialize$1.apply(Serialization.scala:104)
    at scala.util.Try$.apply(Try.scala:161)
    at akka.serialization.Serialization.deserialize(Serialization.scala:98)
    at akka.remote.MessageSerializer$.deserialize(MessageSerializer.scala:23)
    at akka.remote.DefaultMessageDispatcher.payload$lzycompute$1(Endpoint.scala:58)
    at akka.remote.DefaultMessageDispatcher.payload$1(Endpoint.scala:58)
    at akka.remote.DefaultMessageDispatcher.dispatch(Endpoint.scala:76)
    at akka.remote.EndpointReader$$anonfun$receive$2.applyOrElse(Endpoint.scala:935)
    at akka.actor.Actor$class.aroundReceive(Actor.scala:467)
    at akka.remote.EndpointActor.aroundReceive(Endpoint.scala:411)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
    at akka.actor.ActorCell.invoke(ActorCell.scala:487)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238)
    at akka.dispatch.Mailbox.run(Mailbox.scala:220)
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

When using spark-core_2.10 everything works fine.

Answer 1

That errors is due to a mismatch with the scala version.

Spark is compiled for both scala 2.10.x and Spark 2.11.x, if you want to use Scala 2.10, and of course if it is installed in your env you'll be needing the spark-core_2.10, and spark-core_2.11 for Scala 2.11.

PS: At a certain point, I think it was also available for scala 2.9