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https://issues.apache.org/jira/browse/HDFS-6147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13969405#comment-13969405
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Akira AJISAKA commented on HDFS-6147:
-------------------------------------
{code}
+ public static final String DFS_DATANODE_SCAN_USE_RANDOM_INITIAL_KEY =
"dfs.datanode.scan.use.random.initial";;
{code}
There are two semicolons. A semicolon can be removed.
Other than that the patch looks good to me.
> 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
>
>
> 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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