[jira] [Commented] (HDFS-6114) Block Scan log rolling will never happen if blocks written continuously leading to huge size of dncp_block_verification.log.curr

["Vinayakumar B (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-6114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13938981#comment-13938981 ] 

Vinayakumar B commented on HDFS-6114:
-------------------------------------

My proposal is to apply some limit to number of blocks scanned per iteration of {{BlockPoolSliceScanner#scan()}}. So rolling will remove stale entries from verification logs.

Any thoughts..?

> Block Scan log rolling will never happen if blocks written continuously leading to huge size of dncp_block_verification.log.curr
> --------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-6114
>                 URL: https://issues.apache.org/jira/browse/HDFS-6114
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.3.0
>            Reporter: Vinayakumar B
>            Assignee: Vinayakumar B
>            Priority: Critical
>
> 1. {{BlockPoolSliceScanner#scan()}} will not return until all the blocks are scanned. 
> 2. If the blocks (with size in several MBs) to datanode are written continuously 
> then one iteration of {{BlockPoolSliceScanner#scan()}} will be continously scanning the blocks
> 3. These blocks will be deleted after some time (enough to get block scanned)
> 4. As Block Scanning is throttled, So verification of all blocks will take so much time.
> 5. Rolling will never happen, so even though the total number of blocks in datanode doesn't increases, entries ( which contains stale entries of deleted blocks) in *dncp_block_verification.log.curr* continuously increases leading to huge size.
> In one of our env, it grown more than 1TB where total number of blocks were only ~45k.



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