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https://issues.apache.org/jira/browse/HDFS-14563?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16862323#comment-16862323
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Íñigo Goiri commented on HDFS-14563:
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[~jojochuang] can you point to JIRAs or some document?
> 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
>
> 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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