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Date: Sat, 17 Mar 2012 07:23:39 +0000 (UTC)
From: "Lars Hofhansl (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-5569) Do not collect deleted KVs when
 they are still in use by a scanner.
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    [ https://issues.apache.org/jira/browse/HBASE-5569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13231876#comment-13231876 ] 

Lars Hofhansl commented on HBASE-5569:
--------------------------------------

One last point: This seems to be extremely sensitive to the machine it is running on.
Among the various loops I ran on my work machine I ran the test close to 10000 times and have not observed a single failure on that machine (with my changes applied), while on my home machine this is relatively easy to reproduce.

                
> Do not collect deleted KVs when they are still in use by a scanner.
> -------------------------------------------------------------------
>
>                 Key: HBASE-5569
>                 URL: https://issues.apache.org/jira/browse/HBASE-5569
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.0, 0.96.0
>
>         Attachments: 5569-v2.txt, 5569.txt, TestAtomicOperation-output.trunk_120313.rar
>
>
> I noticed this because TestAtomicOperation.testMultiRowMutationMultiThreads fails rarely.
> The solution is similar to HBASE-2856, where expired KVs are not collected when in use by a scanner.
> ---
> What I pieced together so far is that it is the *scanning* side that has problems sometimes.
> Every time I see a assertion failure in the log I see this before:
> {quote}
> 2012-03-12 21:48:49,523 DEBUG [Thread-211] regionserver.StoreScanner(499): Storescanner.peek() is changed where before = rowB/colfamily11:qual1/75366/Put/vlen=6,and after = rowB/colfamily11:qual1/75203/DeleteColumn/vlen=0
> {quote}
> The order of if the Put and Delete is sometimes reversed.
> The test threads should always see exactly one KV, if the "before" was the Put the thread see 0 KVs, if the "before" was the Delete the threads see 2 KVs.
> This debug message comes from StoreScanner to checkReseek. It seems we still some consistency issue with scanning sometimes :(

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