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https://issues.apache.org/jira/browse/HDFS-8950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14715642#comment-14715642
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Daniel Templeton commented on HDFS-8950:
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Thanks! On the last point, I was erring on the side of not modifying the
source tree. If adding new methods only for testing is a preferred to Mockito
acrobatics, then that would simplify things quite a bit. I'll take another
pass.
> NameNode refresh doesn't remove DataNodes
> -----------------------------------------
>
> Key: HDFS-8950
> URL: https://issues.apache.org/jira/browse/HDFS-8950
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode, namenode
> Affects Versions: 2.6.0
> Reporter: Daniel Templeton
> Assignee: Daniel Templeton
> Fix For: 2.8.0
>
> Attachments: HDFS-8950.001.patch, HDFS-8950.002.patch,
> HDFS-8950.003.patch
>
>
> If you remove a DN from NN's allowed host list (HDFS was HA) and then do NN
> refresh, it doesn't remove it actually and the NN UI keeps showing that node.
> It may try to allocate some blocks to that DN as well during an MR job. This
> issue is independent from DN decommission.
> To reproduce:
> 1. Add a DN to dfs_hosts_allow
> 2. Refresh NN
> 3. Start DN. Now NN starts seeing DN.
> 4. Stop DN
> 5. Remove DN from dfs_hosts_allow
> 6. Refresh NN -> NN is still reporting DN as being used by HDFS.
> This is different from decom because there DN is added to exclude list in
> addition to being removed from allowed list, and in that case everything
> works correctly.
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