[HDFS-2093] 1073: Handle case where an entirely empty log is left during NN crash

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Edit log branch (HDFS-1073)
• Fix Version/s: Edit log branch (HDFS-1073)
• Component/s: namenode
• Hadoop Flags: Reviewed
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 21/Jun/11 05:00
• Updated: 24/Jun/11 23:32
• Resolved: 24/Jun/11 23:32

Description

In fault-testing the HDFS-1073 branch, I saw the following situation:

• NN has two storage directories, but one is in failed state
• NN starts to roll edits logs to edits_inprogress_5160285
• NN then crashes
• on restart, it detects the truncated log, but since it has 0 txns, it finalizes it to the nonsense log name edits_5160285-5160284.
• It then starts logs again at edits_inprogress_5160285.
• After this point, no checkpoints or future NN startups succeed since there are two logs starting with the same txid