Currently, the NameNode validates checkpoint uploads by using timestamps associated with checkpoints and edit logs. However, now that we have transaction IDs that uniquely identify each point in time in the history of a namespace, it is more robust to simply use transaction IDs to identify images and edits.
This JIRA is to remove the use of editsTime and checkpointTime and replace it with:
- lastCheckpointTxId - the highest transaction ID reflected in the most recently saved fsimage file
- lastLogRollTxId - the highest transaction ID in edits when rollFsImage was called by the checkpointing node.