[HDFS-1348] Improve NameNode reponsiveness while it is checking if datanode decommissions are complete

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Abandoned
• Component/s: namenode
• Assignee: Hairong Kuang
• Reporter: Hairong Kuang
• Created: 19/Aug/10 22:02
• Updated: 02/Mar/15 22:39
• Resolved: 01/Mar/15 08:10

Description

NameNode normally is busy all the time. Its log is full of activities every second. But once for a while, NameNode seems to pause for more than 10 seconds without doing anything, leaving a blank in its log even though no garbage collection is happening. All other requests to NameNode are blocked when this is happening.

One culprit is DecommionManager. Its monitor holds the fsynamesystem lock during the whole process of checking if decomissioning DataNodes are finished or not, during which it checks every block of up to a default of 5 datanodes.