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From "jiraposter@reviews.apache.org (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5986) Clients can see holes in the META table when regions are being split
Date Thu, 17 May 2012 01:00:32 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13277306#comment-13277306
] 

jiraposter@reviews.apache.org commented on HBASE-5986:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/5133/
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(Updated 2012-05-17 00:58:21.965488)


Review request for hbase.


Changes
-------

v2: 
 - addressed review comments
 - when timeout and interrupt throws RegionOfflineException. 
 - reuse HTable instances in BMSV. 
 - adds close() to MSV assuming it is indeed not public, evolving but private. we should decide
the visibility. 


Summary
-------

We found this issue when running large scale ingestion tests for HBASE-5754. The problem is
that the .META. table updates are not atomic while splitting a region. In SplitTransaction,
there is a time lap between the marking the parent offline, and adding of daughters to the
META table. This can result in clients using MetaScanner, of HTable.getStartEndKeys (used
by the TableInputFormat) missing regions which are made just offline, but the daughters are
not added yet.

This patch is the approach 2 mentioned in the issue comments, mainly during META scan, if
we detect that the region is split, we block until the information for the child regions are
available in META and manually feed those rows to the MetaScanner. Although approach 3 (using
local region transactions) seems cleaner, they are not available under branch 0.92, which
I think should also incorporate this fix. I'll provide ports once we are clear for trunk.


Also this patch does not fix MetaReader (see https://issues.apache.org/jira/browse/HBASE-3475).



This addresses bug HBASE-5986.
    https://issues.apache.org/jira/browse/HBASE-5986


Diffs (updated)
-----

  src/main/java/org/apache/hadoop/hbase/catalog/MetaEditor.java 8873512 
  src/main/java/org/apache/hadoop/hbase/client/HBaseAdmin.java 5d4be3f 
  src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java 5cac9af 
  src/main/java/org/apache/hadoop/hbase/client/HTable.java b8290e4 
  src/main/java/org/apache/hadoop/hbase/client/MetaScanner.java f404999 
  src/main/java/org/apache/hadoop/hbase/master/HMaster.java 0ad9b18 
  src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java 7b4f4a2 
  src/test/java/org/apache/hadoop/hbase/regionserver/TestEndToEndSplitTransaction.java a8091e6


Diff: https://reviews.apache.org/r/5133/diff


Testing
-------

added extensive tests under TestEndToEndSplitTranscation, and ran existing unit tests. 


Thanks,

enis


                
> Clients can see holes in the META table when regions are being split
> --------------------------------------------------------------------
>
>                 Key: HBASE-5986
>                 URL: https://issues.apache.org/jira/browse/HBASE-5986
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.92.1, 0.96.0, 0.94.1
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>         Attachments: HBASE-5986-test_v1.patch
>
>
> We found this issue when running large scale ingestion tests for HBASE-5754. The problem
is that the .META. table updates are not atomic while splitting a region. In SplitTransaction,
there is a time lap between the marking the parent offline, and adding of daughters to the
META table. This can result in clients using MetaScanner, of HTable.getStartEndKeys (used
by the TableInputFormat) missing regions which are made just offline, but the daughters are
not added yet. 
> This is also related to HBASE-4335. 

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