[jira] [Commented] (HDFS-8950) NameNode refresh doesn't remove DataNodes that are no longer in the allowed list

["Kihwal Lee (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-8950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14976605#comment-14976605 ] 

Kihwal Lee commented on HDFS-8950:
----------------------------------

This has been a source of a lot of confusion lately. Should be fixed in 2.7.

> NameNode refresh doesn't remove DataNodes that are no longer in the allowed list
> --------------------------------------------------------------------------------
>
>                 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
>              Labels: 2.7.2-candidate
>             Fix For: 2.8.0
>
>         Attachments: HDFS-8950.001.patch, HDFS-8950.002.patch, HDFS-8950.003.patch, HDFS-8950.004.patch, HDFS-8950.005.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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