When a block is reported from a data node while the block is under construction (i.e. not committed or completed), BlockManager calls BlockInfoUnderConstruction.addReplicaIfNotPresent() to update the reported replica state. But BlockManager is calling it with the stored block, not reported block. This causes the recorded replicas' gen stamp to be that of BlockInfoUnderConstruction itself, not the one from reported replica.
When a pipeline recovery is done for the last packet of a block, the incremental block reports with the new gen stamp may come before the client calling updatePipeline(). If this happens, these replicas will be incorrectly recorded with the old gen stamp and get removed later. The result is close or addAdditionalBlock failure.
If the last block is completed, but the penultimate block is not because of this issue, the file won't be closed. If this file is not cleared, but the client goes away, the lease manager will try to recover the lease/block, at which point it will crash. I will file a separate jira for this shortly.
The worst case is to reject all good ones and accepting a bad one. In this case, the block will get completed, but the data cannot be read until the next full block report containing one of the valid replicas is received.