I am trying to narrow down an Exception thrown by Spark when using "factories" to create classes. See example below ====> only factory2 works!

SparkFactoryNotSerializable.scala

import org.apache.spark.SparkContext
import org.apache.spark.rdd.RDD

/**
 * I am trying to narrow down on an Exception thrown by Spark when using "Factories".
 * The factories have parameters that are used in the classes' functions.
 *
 * To run this code: copy-paste this whole content in a Spark-Shell. Execute Test.theMain(sc)
 *
 */
object Test {

  abstract class A {
    def aFunction: RDD[Int] => RDD[Int]
  }

  /**
   * Creates a class that uses the parameter of the factory directly
   */
  def factory1(i: Int) = new A {
    def aFunction = {
      rdd: RDD[Int] => rdd.map(_ + i)
    }
  }

  /**
   * The class returned that creates an instance's local reference (val) of the parameter
   */
  def factory2(i: Int) = new A {
    val j = i
    def aFunction = {
      rdd: RDD[Int] => rdd.map(_ + j)
    }
  }

  /**
   * Creates a class whose function has a local reference (val) of the parameter
   */
  def factory3(i: Int) = new A {
    def aFunction = {
      rdd: RDD[Int] => { val j = i; rdd.map(_ + j) }
    }
  }

  /**
   * Local reference (val) of the parameter in closure
   */
  def factory4(i: Int) = new A {
    def aFunction = {
      rdd: RDD[Int] => rdd.map { anInt => val j = i; anInt + j }
    }
  }

  def theMain(sc: SparkContext) = {
    val anRDD = sc.parallelize(1 to 9)

    val runningOptions = List(("Factory1", factory1 _), ("Factory2", factory2 _), ("Factory3", factory3 _), ("Factory4", factory4 _))
    runningOptions foreach { case (theName, theFactory) =>
      println(s"RUNNING TEST WITH [${theName}]")
      try {
        val rddPlus2 = theFactory(2)
        val anRDDPlus2 = rddPlus2.aFunction(anRDD)
        (anRDD zip anRDDPlus2).foreach{ case (i, iPlus2) => println(s"[${theName}] i = ${i}, iPlus2 = ${iPlus2}}") }
      }
      catch {
        case e: Exception => println(s"${theName} ERROR ===> ${e.getMessage}")
      }
    }

  }
}

as per discussion today, another thing to try is to access variables in aFunction which is a field in an object. eg. aFunction is an rdd transformer which increments values by both i and MyObject.j. and then with MyObject.j you should try different options of imports (wildcard, specific, with/without renamings) and place them in different places and see which factories work

RUNNING TEST WITH [Factory1]
Factory1 ERROR ===> Task not serializable
RUNNING TEST WITH [Factory2]
Factory2 ERROR ===> Task not serializable
RUNNING TEST WITH [Factory3]
RUNNING TEST WITH [Factory4]
Factory4 ERROR ===> Task not serializable
RUNNING TEST WITH [Factory5]
Factory5 ERROR ===> Task not serializable
RUNNING TEST WITH [Factory6]
defined class A
factory1: (i: Int)A
factory2: (i: Int)A{val j: Int}
factory3: (i: Int)A
factory4: (i: Int)A
factory5: (i: Int)A
factory6: (i: Int)A
anRDD: org.apache.spark.rdd.RDD[Int] = ParallelCollectionRDD[103] at parallelize at <console>:73