Hello, There were a few things which we missing in https://issues.apache.org/jira/browse/FLINK-12539, due to which it was not possible to extend the StreamingFileSink. To fix this I have created a follow-up PR but I am not sure if this is the best way to make these changes: https://github.com/apache/flink/compare/master...kailashhd:FLINK-12539.
In case this is the best approach to do this, I will do ahead and create another JIRA and PR for this. Appreciate the help. Thanks Kailash