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https://issues.apache.org/jira/browse/HDFS-5031?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13763413#comment-13763413
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Arpit Agarwal commented on HDFS-5031:
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Hi Vinay, thanks for the explanation! I apologize for the delay in reviewing
this.
# I ran {{TestDatanodeBlockScanner#testDuplicateScans}} without the rest of the
code changes and it continues to pass. Do you see the same?
# I did not understand how the {{isNewPeriod}} check works. I will continue to
take a look but meanwhile if someone more familiar with this code wants to
chime in please do so.
Minor points:
# {{BlockScanInfo#equals}} looks redundant now. Can we just remove it?
# In {{Reader#next}}, should the assignment to {{lastReadFile}} happen after
the call to {{readNext}}?
> BlockScanner scans the block multiple times and on restart scans everything
> ---------------------------------------------------------------------------
>
> Key: HDFS-5031
> URL: https://issues.apache.org/jira/browse/HDFS-5031
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 3.0.0, 2.1.0-beta
> Reporter: Vinay
> Assignee: Vinay
> Attachments: HDFS-5031.patch
>
>
> BlockScanner scans the block twice, also on restart of datanode scans
> everything.
> Steps:
> 1. Write blocks with interval of more than 5 seconds. write new block on
> completion of scan for written block.
> Each time datanode scans new block, it also scans, previous block which is
> already scanned.
> Now after restart, datanode scans all blocks again.
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