Task not serializable: java.io.NotSerializableException when calling function outside closure only on classes not objects

Question

Getting strange behavior when calling function outside of a closure:

• when function is in a object everything is working
• when function is in a class ge

Answer 1

I solved this problem using a different approach. You simply need to serialize the objects before passing through the closure, and de-serialize afterwards. This approach just works, even if your classes aren't Serializable, because it uses Kryo behind the scenes. All you need is some curry. ;)

Here's an example of how I did it:

def genMapper(kryoWrapper: KryoSerializationWrapper[(Foo => Bar)])
               (foo: Foo) : Bar = {
    kryoWrapper.value.apply(foo)
}
val mapper = genMapper(KryoSerializationWrapper(new Blah(abc))) _
rdd.flatMap(mapper).collectAsMap()

object Blah(abc: ABC) extends (Foo => Bar) {
    def apply(foo: Foo) : Bar = { //This is the real function }
}

Feel free to make Blah as complicated as you want, class, companion object, nested classes, references to multiple 3rd party libs.

KryoSerializationWrapper refers to: https://github.com/amplab/shark/blob/master/src/main/scala/shark/execution/serialization/KryoSerializationWrapper.scala