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From "Chen Liang (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (HDFS-11586) Report %free, %write_locked, %read_locked for the NameNode FSNamesystemLock
Date Mon, 03 Apr 2017 18:24:42 GMT

     [ https://issues.apache.org/jira/browse/HDFS-11586?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chen Liang reassigned HDFS-11586:
---------------------------------

    Assignee: Chen Liang

> 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
>            Assignee: Chen Liang
>            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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