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Posted to hdfs-dev@hadoop.apache.org by "Zheng Shao (JIRA)" <ji...@apache.org> on 2017/03/28 06:23:41 UTC

[jira] [Created] (HDFS-11586) Report %free, %write_locked, %read_locked for the NameNode FSNamesystemLock

Zheng Shao created HDFS-11586:
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             Summary: Report %free, %write_locked, %read_locked for the NameNode FSNamesystemLock
                 Key: HDFS-11586
                 URL: https://issues.apache.org/jira/browse/HDFS-11586
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: namenode
            Reporter: Zheng Shao
            Priority: Minor


It's useful to understand how busy the NameNode is by providing these metrics, similar to the %util number from iostat for disks.

When %free goes to close to 0, we know the NameNode is congested (just like when disk %util goes to 100%).

This can be implemented very cheaply by using a thread that wakes up every 10ms to check FSNamesystemLock's getReadLockCount() and isWriteLocked() (via the member coarseLock).





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