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From "Nick Dimiduk (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13938) Deletes done during the region merge transaction may get eclipsed
Date Mon, 22 Jun 2015 18:34:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13938?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14596383#comment-14596383
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Nick Dimiduk commented on HBASE-13938:
--------------------------------------

I think this is not needed on master because meta updates are run from master.

> Deletes done during the region merge transaction may get eclipsed
> -----------------------------------------------------------------
>
>                 Key: HBASE-13938
>                 URL: https://issues.apache.org/jira/browse/HBASE-13938
>             Project: HBase
>          Issue Type: Bug
>          Components: master, regionserver
>            Reporter: Devaraj Das
>            Assignee: Enis Soztutar
>             Fix For: 2.0.0, 1.2.0, 1.1.1, 1.3.0
>
>         Attachments: 13938-branch-1.1.txt, hbase-13938_v2-branch-1.1.patch, hbase-13938_v3-branch-1.1.patch
>
>
> Was looking at an issue from our internal testing. It seems the Deletes of the region
rows from the meta done during the merge transaction could be eclipsed by the Put of a region
row that might have happened moments before.
> The master logs this for the merge:
> {noformat}
> 2015-06-18 13:13:46,018 INFO  [AM.ZK.Worker-pool2-t12] master.AssignmentManager: Handled
MERGED event; merged=IntegrationTestIngest,a666665c,1434633226681.0927319db6bf5e128e3bec2a420819aa.,
region_a=IntegrationTestIngest,a666665c,1434631353820.8b911862d7705ac808b8d132d0154c16., region_b=IntegrationTestIngest,acccccc2,1434631353820.1bdaf759862f45d133ef77fdbda21aec.,
on ddas-2-5.openstacklocal,16020,1434632778438
> {noformat}
> One of the regions that got merged got Opened a few seconds back:
> {noformat}
> 2015-06-18 13:13:46,591 INFO  [RS_OPEN_REGION-ddas-2-5:16020-1] regionserver.HRegion:
Onlined 1bdaf759862f45d133ef77fdbda21aec; next sequenceid=182988
> {noformat}
> The above would have done a Put in the meta.
> Looking at the raw scan of the meta, for the new merged region, the creation timestamp
is 1434633226101:
> {noformat}
>  IntegrationTestIngest,a666665c,1434633226681.0927319db6bf5e128e3bec2a420819aa. column=info:regioninfo,
timestamp=1434633226101, value={ENCODED => 0927319db6bf5e128e3bec2a420819aa, NAME =>
'IntegrationTestIngest,a666665c,1434633226681.0927319db6bf5e128e3bec2a420819aa.', STARTKEY
=> 'a666665c', ENDKEY => 'b3333328'}
> {noformat}
> Looking at the raw scan of the meta, the timestamp for the region open of the already
merged region is 1434633226600. This is a little after the merge transaction's timestamp.
> {noformat}
> IntegrationTestIngest,acccccc2,1434631353820.1bdaf759862f45d133ef77fdbda21aec. column=info:seqnumDuringOpen,
timestamp=1434633226600, value=\x00\x00\x00\x00\x00\x02\xCA\xCC
>  IntegrationTestIngest,acccccc2,1434631353820.1bdaf759862f45d133ef77fdbda21aec. column=info:server,
timestamp=1434633226600, value=ddas-2-5.openstacklocal:16020
>  IntegrationTestIngest,acccccc2,1434631353820.1bdaf759862f45d133ef77fdbda21aec. column=info:serverstartcode,
timestamp=1434633226600, value=1434632778438
> {noformat}
> We need to fix it so that the merge region transaction also takes the master's timestamp.
Similar to HBASE-13875.
> When this happens, clients start to see a row in the meta with an empty HRegionInfo (this
is because the Put done during the region open only updates the location information but not
the HRI, and the HRI deleted during the merge transaction "remains deleted").



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