Supporting Kryo registration in DSv2

[Andrew Melo]

Hello all,

Is there a way to register classes within a datasourcev2 implementation in
the Kryo serializer?

I've attempted the following in both the constructor and static block of my
toplevel class:

        SparkContext context = SparkContext.getOrCreate();
        SparkConf conf = context.getConf();
        Class[] classesRegistered = new Class[] {
                edu.vanderbilt.accre.laurelin.spark_ttree.Reader.class,
                edu.vanderbilt.accre.laurelin.spark_ttree.Partition.class,
                edu.vanderbilt.accre.laurelin.spark_ttree.SlimTBranch.class
                };
        conf.registerKryoClasses(classesRegistered);

But (if I'm reading correctly), this is too late, since the config has
already been parsed while initializing the SparkContext, adding classes to
the SparkConf has no effect. From what I can tell, the kryo instance behind
is private, so I can't add the registration manually either.

Any thoughts?
Thanks
Andrew