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Posted to hdfs-issues@hadoop.apache.org by "Xiaoyu Yao (JIRA)" <ji...@apache.org> on 2015/11/17 01:50:11 UTC

[jira] [Commented] (HDFS-9434) Recommission a datanode with 500k blocks may pause NN for 30 seconds

    [ https://issues.apache.org/jira/browse/HDFS-9434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15007721#comment-15007721 ] 

Xiaoyu Yao commented on HDFS-9434:
----------------------------------

Thanks [~szetszwo] for reporting the issue and posting the fix. The patch LGTM. 
+1 pending Jenkins.

> Recommission a datanode with 500k blocks may pause NN for 30 seconds
> --------------------------------------------------------------------
>
>                 Key: HDFS-9434
>                 URL: https://issues.apache.org/jira/browse/HDFS-9434
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: Tsz Wo Nicholas Sze
>            Assignee: Tsz Wo Nicholas Sze
>         Attachments: h9434_20151116.patch
>
>
> In BlockManager, processOverReplicatedBlocksOnReCommission is called within the namespace lock.  There is a (not very useful) log message printed in processOverReplicatedBlock.  When there is a large number of blocks stored in a storage, printing the log message for each block can pause NN to process any other operations.  We did see that it could pause NN  for 30 seconds for a storage with 500k blocks.
> I suggest to change the log message to trace level as a quick fix.



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