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From "amith (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-3512) Delay in scanning blocks at DN side when there are huge number of blocks
Date Thu, 07 Jun 2012 14:42:27 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3512?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

amith updated HDFS-3512:
------------------------

    Attachment: HDFS-3512.patch

Currently we are adding some random time when the block is getting added into blockInfoSet,
this randomization will be for a very short period of time i.e, till the block is scanned
for the first time, after first scan it will update the exact time of scan so I thought of
removing the random and verified the block scanning for 75K blocks which worked fine.

I tried to write a test for the same but couldn't since I can't determine the random number
generated and added.

@Suja can u just apply the patch and test the same
                
> Delay in scanning blocks at DN side when there are huge number of blocks
> ------------------------------------------------------------------------
>
>                 Key: HDFS-3512
>                 URL: https://issues.apache.org/jira/browse/HDFS-3512
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 2.0.1-alpha
>            Reporter: suja s
>            Assignee: amith
>         Attachments: HDFS-3512.patch
>
>
> Block scanner maintains the full list of blocks at DN side in a map and there is no differentiation
between the blocks which are already scanned and the ones not scanend. For every check (ie
every 5 secs) it will pick one block and scan. There are chances that it chooses a block which
is already scanned which leads to further delay in scanning of blcoks which are yet to be
scanned.

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