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From "Eric Payne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3828) Block Scanner rescans blocks too frequently
Date Tue, 22 Apr 2014 21:42:18 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13977481#comment-13977481
] 

Eric Payne commented on HDFS-3828:
----------------------------------

[~adi2] and [~eli]

I am working through the backlog of 0.23 issues. Since the patch for this issue has been merged
to trunk and branch-2, can we close this JIRA? I don't think it is needed for branch 23.

Please comment by Friday, April 25



> Block Scanner rescans blocks too frequently
> -------------------------------------------
>
>                 Key: HDFS-3828
>                 URL: https://issues.apache.org/jira/browse/HDFS-3828
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 0.23.0
>            Reporter: Andy Isaacson
>            Assignee: Andy Isaacson
>             Fix For: 2.5.0
>
>         Attachments: hdfs-3828-1.txt, hdfs-3828-2.txt, hdfs-3828-3.txt, hdfs3828.txt
>
>
> {{BlockPoolSliceScanner#scan}} calls cleanUp every time it's invoked from {{DataBlockScanner#run}}
via {{scanBlockPoolSlice}}.  But cleanUp unconditionally roll()s the verificationLogs, so
after two iterations we have lost the first iteration of block verification times.  As a result
a cluster with just one block repeatedly rescans it every 10 seconds:
> {noformat}
> 2012-08-16 15:59:57,884 INFO  datanode.BlockPoolSliceScanner (BlockPoolSliceScanner.java:verifyBlock(391))
- Verification succeeded for BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> 2012-08-16 16:00:07,904 INFO  datanode.BlockPoolSliceScanner (BlockPoolSliceScanner.java:verifyBlock(391))
- Verification succeeded for BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> 2012-08-16 16:00:17,925 INFO  datanode.BlockPoolSliceScanner (BlockPoolSliceScanner.java:verifyBlock(391))
- Verification succeeded for BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> {noformat}
> {quote}
> To fix this, we need to avoid roll()ing the logs multiple times per period.



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