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https://issues.apache.org/jira/browse/HDFS-14563?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kihwal Lee updated HDFS-14563:
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    Attachment: mt_mode-2.txt

> Enhance interface about recommissioning/decommissioning
> -------------------------------------------------------
>
>                 Key: HDFS-14563
>                 URL: https://issues.apache.org/jira/browse/HDFS-14563
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client, namenode
>            Reporter: He Xiaoqiao
>            Assignee: He Xiaoqiao
>            Priority: Major
>         Attachments: HDFS-14563.001.patch, HDFS-14563.002.patch, mt_mode-2.txt
>
>
> In current implementation, if we need to decommissioning or recommissioning 
> one datanode, the only way is add the datanode to include or exclude file 
> under namenode configuration path then execute command `bin/hadoop dfsadmin 
> -refreshNodes` and trigger namenode to reload include/exclude and start to 
> recommissioning or decommissioning datanode.
> The shortcomings of this approach is that:
> a. namenode reload include/exclude configuration file from devices, if I/O 
> load is high, handler may be blocked.
> b. namenode has to process every datnodes in include and exclude 
> configurations, if there are many datanodes (very common for large cluster) 
> pending to process, namenode will be hung for hundred seconds to wait 
> recommision/decommision finish at the worst since holding write lock.
> I think we should expose one lightweight interface to support recommissioning 
> or decommissioning single datanode, thus we can operate datanode using 
> dfsadmin more smooth.



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