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https://issues.apache.org/jira/browse/HDFS-7411?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14313355#comment-14313355
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Tsz Wo Nicholas Sze commented on HDFS-7411:
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> Since the decom manager iterates over the whole datanode list, both live and
> decommissioning nodes count towards the limit. Thus, the actual number of
> decomming nodes processed varies between 0 and the limit.
I agree that live node should not be counted. It is a bug in the node based
decommission logic and we probably should fix the bug.
A problem for translating node-based to block-based decommission is that there
is no good choice of number of nodes per block. It may result in surprising
behavior for clusters extremely large or extremely small. This is a reason
that we want to keep the old code.
A second reason is that the old code is proven to be working. If we remove it
now and then find a serious bug in this patch after a release, then we don't
have anything to fallback. That's why the standard procedure to remove an
existing feature is to deprecate it first and the remove it later.
> Refactor and improve decommissioning logic into DecommissionManager
> -------------------------------------------------------------------
>
> Key: HDFS-7411
> URL: https://issues.apache.org/jira/browse/HDFS-7411
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.5.1
> Reporter: Andrew Wang
> Assignee: Andrew Wang
> Attachments: hdfs-7411.001.patch, hdfs-7411.002.patch,
> hdfs-7411.003.patch, hdfs-7411.004.patch, hdfs-7411.005.patch,
> hdfs-7411.006.patch, hdfs-7411.007.patch, hdfs-7411.008.patch,
> hdfs-7411.009.patch, hdfs-7411.010.patch
>
>
> Would be nice to split out decommission logic from DatanodeManager to
> DecommissionManager.
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