Hi all, I look at the source code of Hadoop, and found that the InputSplit did not implements Writable. As my understanding, InputSplit will been transfered to each TT and then deserialized. So it should implement the Writable interface. And I check each implementation of InputSplit, actually all the sub-classes implement the Writable interface. So I think it would be better to to let the abstract class InputForamt implement the Writable, then users won't forget to implement the method write(DataOutput out) and readFields(DataInput in) if he wants to write a customized InputSplit.
-- Best Regards Jeff Zhang
