Hi Amol,
The implementation of the RichSinkFunction probably contains a field that is not serializable. To avoid serializable exception, you can:
1. Marking the field as transient. This makes the serialization mechanism skip the field.
2. If the field is part of the object's persistent state, the type of the field must implement Serializable.
Furthermore, you can remove some fields to locate the problem fields.
Best, Hequn