[HDFS-2972] HA: small optimization building incremental block report

• Type: Sub-task
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: HA branch (HDFS-1623)
• Fix Version/s: HA branch (HDFS-1623)
• Component/s: datanode, ha
• Target Version/s: HA branch (HDFS-1623)
• Hadoop Flags: Reviewed
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 18/Feb/12 00:31
• Updated: 23/Feb/12 12:54
• Resolved: 22/Feb/12 20:37

Description

Current the incremental block report is a List. However, we only really need to send the most recent information for each block. So, if a block becomes RBW and is then becomes FINALIZED before the next incremental block report, we should just report the FINALIZED replica. It's an easy change to just switch to a map by blockid.
This is on the HA branch since HA changes the code to send RBWs in the incremental reports, hence it's more important for maintaining performance parity with trunk.