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Date: Fri, 7 Oct 2011 18:48:32 +0000 (UTC)
From: "jiraposter@reviews.apache.org (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-4377) [hbck] Offline rebuild .META. from
 fs data only.
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    [ https://issues.apache.org/jira/browse/HBASE-4377?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13123059#comment-13123059 ] 

jiraposter@reviews.apache.org commented on HBASE-4377:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/2126/
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(Updated 2011-10-07 18:46:54.806909)


Review request for hbase, Michael Stack and Andrew Purtell.


Changes
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Updates with nits and separated tests into different classes so that we can rely on new jvms to avoid OO file handle errors intermittently encountered when shutting down and restarting mini clusters.


Summary
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commit fbf82c17be6b3ecca5a981f5270cf93aac26e479
Author: Jonathan Hsieh <jon@cloudera.com>
Date:   Wed Sep 28 10:18:11 2011 -0700

    HBASE-4377 [hbck] Offline rebuild .META. from fs data only
    

This patch rebuilds a new .META. table by reading all the .regioninfo files in the hbase main directory.  It depends on the yet to be committed HBASE-4515 (either my verison or Gary's version), HBASE-4509, and HBASE-4506.  

Some follow on work includes backporting to 0.90, auto-patching true holes, and adding documentation.


This addresses bug HBASE-4377.
    https://issues.apache.org/jira/browse/HBASE-4377


Diffs (updated)
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  src/main/java/org/apache/hadoop/hbase/master/MasterFileSystem.java b9c850d 
  src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java 154ac32 
  src/main/java/org/apache/hadoop/hbase/util/hbck/OfflineMetaRepair.java PRE-CREATION 
  src/test/java/org/apache/hadoop/hbase/util/TestHBaseFsck.java f5be448 
  src/test/java/org/apache/hadoop/hbase/util/hbck/HbckTestingUtil.java PRE-CREATION 
  src/test/java/org/apache/hadoop/hbase/util/hbck/OfflineMetaRebuildTestCore.java PRE-CREATION 
  src/test/java/org/apache/hadoop/hbase/util/hbck/TestOfflineMetaRebuildBase.java PRE-CREATION 
  src/test/java/org/apache/hadoop/hbase/util/hbck/TestOfflineMetaRebuildHole.java PRE-CREATION 
  src/test/java/org/apache/hadoop/hbase/util/hbck/TestOfflineMetaRebuildOverlap.java PRE-CREATION 

Diff: https://reviews.apache.org/r/2126/diff


Testing
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An earlier version of this code (backported to 0.90) was used to diagnose and repair a cluster that had 2700 inconsistencies due to failed splits (the cluster was underprovisioned memory-wise, and on restart, the some regions would start splitting and then die due to oome's).  This was not actually used on a live cluster -- it was used to reconstruct a .META. from .regioninfo's laid out in hbase's directory structure.

Note also that this is not an automatic fix -- whenever any problems are found, this bails out but dumps info on holes, suggests some fixes, and displays sets of overlapping regions.  It is up to the user to merge regions, to create .regioninfo files to plug hole, and to do any potential data loosing operations.

The tests demonstrate current expected behavior -- rebuild meta if things line up, and fail without making modifications if holes or overlaps exist.


Thanks,

jmhsieh


> [hbck] Offline rebuild .META. from fs data only.
> ------------------------------------------------
>
>                 Key: HBASE-4377
>                 URL: https://issues.apache.org/jira/browse/HBASE-4377
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Jonathan Hsieh
>            Assignee: Jonathan Hsieh
>         Attachments: 0001-HBASE-4377-hbck-Offline-rebuild-.META.-from-fs-data-.patch, hbase-4377-trunk.v2.patch
>
>
> In a worst case situation, it may be helpful to have an offline .META. rebuilder that just looks at the file system's .regioninfos and rebuilds meta from scratch.  Users could move bad regions out until there is a clean rebuild.  
> It would likely fill in region split holes.  Follow on work could given options to merge or select regions that overlap, or do online rebuilds.

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