HADOOP-3981 introduces a distributed file checksum algorithm. It's designed for replicated block.
DFSClient.getFileChecksum() need some updates, so it can work for striped block group.
Make existing DFSClient#getFileChecksum() work for striped blocks
Erasure coding: recomputing block checksum on the fly by reconstructing the missed/corrupt block data
Refactor DFSClient#getFileChecksum and DataXceiver#blockChecksum
Refine the behaviour of getFileChecksum when length = 0