[HDFS-1447] Make getGenerationStampFromFile() more efficient, so it doesn't reprocess full directory listing for every block

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.20.2
• Component/s: datanode
• Tags: datanode startup
• Assignee: Matthew Foley
• Reporter: Matthew Foley
• Created: 07/Oct/10 22:55
• Updated: 01/Mar/15 06:59

Description

Make getGenerationStampFromFile() more efficient. Currently this routine is called by addToReplicasMap() for every blockfile in the directory tree, and it walks each file's containing directory on every call. There is a simple refactoring that should make it more efficient.

This work item is one of four sub-tasks for HDFS-1443, Improve Datanode startup time.
The fix will probably be folded into sibling task HDFS-1446, which is already refactoring the method that calls getGenerationStampFromFile().