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From "Eric Payne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9945) Datanode command for evicting writers
Date Wed, 06 Apr 2016 20:00:28 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15228984#comment-15228984
] 

Eric Payne commented on HDFS-9945:
----------------------------------

Thanks, [~kihwal], for providing this feature. The patch looks good to me.

+1. I will commit to trunk, branch-2, and branch-2.8

> Datanode command for evicting writers
> -------------------------------------
>
>                 Key: HDFS-9945
>                 URL: https://issues.apache.org/jira/browse/HDFS-9945
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: datanode
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>         Attachments: HDFS-9945.patch, HDFS-9945.v2.patch
>
>
> It will be useful if there is a command to evict writers from a datanode. When a set
of datanodes are being decommissioned, they can get blocked by slow writers at the end.  It
was rare in the old days since mapred jobs didn't last too long, but with many different types
of apps running on today's YARN cluster, we are often see very long tail in datanode decommissioning.
> I propose a new dfsadmin command, {{evictWriters}}, to be added. I initially thought
about having namenode automatically telling datanodes on decommissioning, but realized that
having a command is more flexible. E.g. users can choose not to do this at all, choose when
to evict writers, or whether to try multiple times for whatever reasons.



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