[HDFS-2001] HDFS-1073: Kill previous.checkpoint, lastcheckpoint.tmp directories

• 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: 25/May/11 23:38
• Updated: 27/May/11 20:48
• Resolved: 27/May/11 20:48

Description

In the old design for edits/image storage, the secondary namenode does a complicated dance of moving "current/" to "lastcheckpoint.tmp", checkpointing into "current/", then moving "lastcheckpoint.tmp" back to "previous.checkpoint". The idea here was so that there would always be one directory with a valid set of storage files.

In the HDFS-1073 design, this complicated dance isn't necessary. If a checkpoint fails, we can just rm that single fsimage_N.ckpt file and still be left with a valid storage directory.

So, we can just let the 2NN keep a single current/ dir around for all checkpoints and eliminate the complexity of the dance.