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Date: Fri, 13 May 2011 19:05:47 +0000 (UTC)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-1332) When unable to place replicas,
 BlockPlacementPolicy should log reasons nodes were excluded
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    [ https://issues.apache.org/jira/browse/HDFS-1332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13033220#comment-13033220 ] 

Tsz Wo (Nicholas), SZE commented on HDFS-1332:
----------------------------------------------

Ted, please correct me if I am wrong: {{NNThroughputBenchmark}} does not count replication and GC.

> How about adding a static boolean, blockPlacementDebug, ...

I actually like your idea.  In Hadoop, we use log levels for such purpose.  That why I suggest adding {{BlockPlacementPolicyDefault.LOG}} (It probably is better to add the log in {{BlockPlacementPolicy.LOG}}).  How does it sound to you?

> When unable to place replicas, BlockPlacementPolicy should log reasons nodes were excluded
> ------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1332
>                 URL: https://issues.apache.org/jira/browse/HDFS-1332
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: Todd Lipcon
>            Assignee: Ted Yu
>            Priority: Minor
>              Labels: newbie
>             Fix For: 0.23.0
>
>         Attachments: HDFS-1332.patch
>
>
> Whenever the block placement policy determines that a node is not a "good target" it could add the reason for exclusion to a list, and then when we log "Not able to place enough replicas" we could say why each node was refused. This would help new users who are having issues on pseudo-distributed (eg because their data dir is on /tmp and /tmp is full). Right now it's very difficult to figure out the issue.

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