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https://issues.apache.org/jira/browse/HADOOP-8928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13503348#comment-13503348
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liang xie commented on HADOOP-8928:
-----------------------------------
After applied the patch, we can update the rack config script or file, then
issue "hdfs dfsadmin -refreshTopology", then startup the new datanode, it'll
register to namenode successfully, w/o to restart namenode:)
I tested both ScriptBasedMapping and TableMapping impl, all is OK
There's a nit for "load()" in new TableMapping class, it'll be invoked many
times while cluster starting or refreshTopology, but it's not a big issue,
cause the OS page cache will reduce the physical IO ops while cluster starting.
> Add ability to reset topologies on master nodes
> -----------------------------------------------
>
> Key: HADOOP-8928
> URL: https://issues.apache.org/jira/browse/HADOOP-8928
> Project: Hadoop Common
> Issue Type: Improvement
> Components: net
> Affects Versions: 3.0.0, 2.0.2-alpha
> Reporter: Shinichi Yamashita
> Attachments: HADOOP-8928.txt
>
>
> For a topology decision of DataNode and TaskTracker, ScriptBasedMapping
> (probably TableMapping) confirms HashMap first.
> To decide topology of DataNode and TaskTracker again, it is necessary to
> restart NameNode and JobTracker.
> Therefore, it is necessary to change (or clear) HashMap function without
> restarting NameNode and JobTracker.
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