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Date: Thu, 24 Apr 2014 06:06:15 +0000 (UTC)
From: "Akira AJISAKA (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12703149.1395651073668.169685.1398319575850@arcas>
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References: <JIRA.12703149.1395651073668@arcas>
Subject: [jira] [Commented] (HDFS-6147) New blocks scanning will be delayed
 due to issue in BlockPoolSliceScanner#updateBytesToScan(..)
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    [ https://issues.apache.org/jira/browse/HDFS-6147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13979332#comment-13979332 ] 

Akira AJISAKA commented on HDFS-6147:
-------------------------------------

Thanks [~vinayrpet] for the update. +1 (non-binding).
In addition, Jenkins said +1 for the patch. https://builds.apache.org/job/PreCommit-HDFS-Build/6700/

> New blocks scanning will be delayed due to issue in BlockPoolSliceScanner#updateBytesToScan(..)
> -----------------------------------------------------------------------------------------------
>
>                 Key: HDFS-6147
>                 URL: https://issues.apache.org/jira/browse/HDFS-6147
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.4.0
>            Reporter: Vinayakumar B
>            Assignee: Vinayakumar B
>         Attachments: HDFS-6147.patch, HDFS-6147.patch, HDFS-6147.patch
>
>
> New blocks scanning will be delayed if old blocks deleted after datanode restart.
> Steps:
> 1. Write some blocks and wait till all scans over
> 2. Restart the datanode
> 3. Delete some of the blocks
> 4. Write new blocks which are less in size compared to deleted blocks.
> Problem:
> {{BlockPoolSliceScanner#updateBytesToScan(..)}} updates {{bytesLeft}} based on following comparison
> {code}   if (lastScanTime < currentPeriodStart) {
>       bytesLeft += len;
>     }{code}
> But in {{BlockPoolSliceScanner#assignInitialVerificationTimes()}} {{bytesLeft}} decremented using below comparison
> {code}if (now - entry.verificationTime < scanPeriod) {{code}
> Hence when the old blocks are deleted {{bytesLeft}} going negative.
> new blocks will not be scanned until it becomes positive again.
> So in both places verificationtime should be compared against scanperiod.


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