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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7671) Flushing memstore again after last failure could cause data loss
Date Fri, 01 Feb 2013 17:48:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13568906#comment-13568906
] 

stack commented on HBASE-7671:
------------------------------

One question. You check the stopped flag rather than abort flag.  Don't we set the stop flag
when we are shutting down the server cleanly?  And as part of clean shutdown, don't we want
to flush?  If so, should we be checking the abort flag rather than the stop flag?

Overall, I think this a better approach.  Less moving parts.  Nice test.  Do you think it
possible we could fail a flush, near immediately succeed a flush, and only then set the abort
flag?  (abort flag is volatile at least).

Good stuff Chunhui
                
> Flushing memstore again after last failure could cause data loss
> ----------------------------------------------------------------
>
>                 Key: HBASE-7671
>                 URL: https://issues.apache.org/jira/browse/HBASE-7671
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.94.4
>            Reporter: chunhui shen
>            Assignee: chunhui shen
>            Priority: Critical
>             Fix For: 0.96.0, 0.94.6
>
>         Attachments: HBASE-7671.patch, HBASE-7671v2.patch, HBASE-7671v3.patch, HBASE-7671v4.patch
>
>
> See the following logs first:
> {code}
> 2013-01-23 18:58:38,801 INFO org.apache.hadoop.hbase.regionserver.Store: Flushed , sequenceid=9746535080,
memsize=101.8m, into tmp file hdfs://dw77.kgb.sqa.cm4:9900/hbase-test3/writetest1/8dc14e35b4d7c0e481e0bb30849cff7d/.tmp/bebeeecc56364b6c8126cf1dc6782a25
> 2013-01-23 18:58:41,982 WARN org.apache.hadoop.hbase.regionserver.MemStore: Snapshot
called again without clearing previous. Doing nothing. Another ongoing flush or did we fail
last attempt?
> 2013-01-23 18:58:43,274 INFO org.apache.hadoop.hbase.regionserver.Store: Flushed , sequenceid=9746599334,
memsize=101.8m, into tmp file hdfs://dw77.kgb.sqa.cm4:9900/hbase-test3/writetest1/8dc14e35b4d7c0e481e0bb30849cff7d/.tmp/4eede32dc469480bb3d469aaff332313
> {code}
> The first time memstore flush is failed when commitFile()(Logged the first edit above),
then trigger server abort, but another flush is coming immediately(could caused by move/split,Logged
the third edit above) and successful.
> For the same memstore's snapshot, we get different sequenceid, it causes data loss when
replaying log edits
> See details from the unit test case in the patch

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