I would like to do some additional performance related changes to the CassandraIO module, but it would necessitate changing the Mapper interface to return ListenableFuture opposed to java.util.concurrent.Future. I'm not sure why the Mapper interface specifies the former, as the datastax driver itself returns a ListenableFuture for any async queries.
How are changes to user facing interfaces handled (however minor they would be) for Beam? If this is something that can be done, I'm happy to create a ticket, but supporting full backwards compatibility might be too much work. *~Vincent*
