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https://issues.apache.org/jira/browse/HDFS-1348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12916276#action_12916276
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Dmytro Molkov commented on HDFS-1348:
-------------------------------------

The patch looks good to me. +1

> Improve NameNode reponsiveness while it is checking if datanode decommissions 
> are complete
> ------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1348
>                 URL: https://issues.apache.org/jira/browse/HDFS-1348
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.22.0
>
>         Attachments: decomissionImp1.patch, decomissionImp2.patch, 
> decommission.patch, decommission1.patch
>
>
> 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.

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