Hi @mmuru ,
my post was hidden but reinstated today and I had exact the problem: [Dask on Ray] Parallelizing Rasa's DaskGraphRunner - Problem with serializing SQLAlchemy objects
I needed to write custom serializers that omit serializing the DB connections because they are not serializable.
What you also probably need is to check serializability with inspect_serializability function (Serialization — Ray v1.9.2).