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https://issues.apache.org/jira/browse/HDFS-7411?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14302513#comment-14302513
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Aaron T. Myers commented on HDFS-7411:
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bq. Users are familiar with the existing behavior so that we have to keep the
old code, deprecate them first and then remove them later. It is a standard
procedure for changing the behavior of a feature. No?
I think it's pretty common for us to change the behavior of the system when the
behavior change is a strict improvement. Keeping around inferior behavior just
for the purpose of consistency seems rather pointless.
For example, it used to be the case that fsimage transfers from the secondary
or standby NN happened with a GET request from the standby to the active, which
then triggered another GET request back from the active to the standby. When we
did the work to make the transfer work with just a single POST request from the
standby to the active, we didn't bother keeping around the old GET/GET behavior
just because people were used to it.
Similarly, when we find ways that CPU performance or memory usage in the NN can
be improved, we don't keep around the old ways of doing things just because
operators might be used to the NN being slow or using a lot of memory.
bq. -1 on the patch.
As [~andrew.wang] has already described, the new behavior should be both more
performant and more predictable. I don't know see why we'd want to keep around
decommissioning behavior that can be both erratic and slower.
Andrew already quite graciously amended the patch to preserve the backward
compatibility of {{dfs.namenode.decommission.nodes.per.interval}} per your
request, [~szetszwo]. I would hope that would have satisfied your feedback.
Please consider withdrawing your -1.
> 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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