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From "Kannan Muthukkaruppan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2244) META get inconsistent in a number of crash scenarios
Date Sat, 20 Feb 2010 02:09:28 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2244?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12836100#action_12836100
] 

Kannan Muthukkaruppan commented on HBASE-2244:
----------------------------------------------

Stack wrote <<<The report of split is not atomic; we are sending 3 separate puts.
We don't have means of making a cross-row transaction out of this operation>>>.

Would keeping all region info for a table as columns under a single row key in .META. be such
a crazy idea? With that you can do atomic mutations to a given table's region info. The cons
would be that entire "rowkey" would be hosted on a single server... but for most tables that'd
probably already be the case unless it has an exorbitant number of regions.

To which Stack responded with: <<<< For sure, lets do something in 0.20. I think
metascanner when it runs can check an offlined region. If its not followed by two daughters
- it has the necessary info as columns splitA and splitB - it can add them. Let me take a
closer look. Will report back.

Having all in the one row is a bit radical. Gets and puts would each take out a row lock.
I think this might slow down all .META. lookups. We also have a mechanism for getting the
row closest to the asked for one. Its used for figuring out which region a row sits in. This
would have to be recast if all was in the one row.>>>>



> META get inconsistent in a number of crash scenarios
> ----------------------------------------------------
>
>                 Key: HBASE-2244
>                 URL: https://issues.apache.org/jira/browse/HBASE-2244
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: Kannan Muthukkaruppan
>            Priority: Critical
>             Fix For: 0.20.4
>
>
> (Forking this issue off from HBASE-2235).
> During load testing, in a number of failure scenarios (unexpected region server deaths)
etc., we notice that META can get inconsistent. This primarily happens for regions which are
in the process of being split. Manually running add_table.rb seems to fix the tables meta
data just fine. 
> But it would be good to do automatic cleansing (as part of META scanners work) and/or
avoid these inconsistent states altogether.
> For example, for a particular startkey, I see all these entries:
> {code}
> test1,1204765,1266569946560 column=info:regioninfo, timestamp=1266581302018, value=REGION
=> {NAME => 'test1,
>                              1204765,1266569946560', STARTKEY => '1204765', ENDKEY
=> '1441091', ENCODED => 18
>                              19368969, OFFLINE => true, SPLIT => true, TABLE =>
{{NAME => 'test1', FAMILIES =>
>                               [{NAME => 'actions', VERSIONS => '3', COMPRESSION
=> 'NONE', TTL => '2147483647'
>                              , BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE
=> 'true'}]}}
>  test1,1204765,1266569946560 column=info:server, timestamp=1266570029133, value=10.129.68.212:60020
>  test1,1204765,1266569946560 column=info:serverstartcode, timestamp=1266570029133, value=1266562597546
>  test1,1204765,1266569946560 column=info:splitB, timestamp=1266581302018, value=\x00\x071441091\x00\x00\x00\x0
>                              1\x26\xE6\x1F\xDF\x27\x1Btest1,1290703,1266581233447\x00\x071290703\x00\x00\x00\x
>                              05\x05test1\x00\x00\x00\x00\x00\x02\x00\x00\x00\x07IS_ROOT\x00\x00\x00\x05false\x
>                              00\x00\x00\x07IS_META\x00\x00\x00\x05false\x00\x00\x00\x01\x07\x07actions\x00\x00
>                              \x00\x07\x00\x00\x00\x0BBLOOMFILTER\x00\x00\x00\x05false\x00\x00\x00\x0BCOMPRESSI
>                              ON\x00\x00\x00\x04NONE\x00\x00\x00\x08VERSIONS\x00\x00\x00\x013\x00\x00\x00\x03TT
>                              L\x00\x00\x00\x0A2147483647\x00\x00\x00\x09BLOCKSIZE\x00\x00\x00\x0565536\x00\x00
>                              \x00\x09IN_MEMORY\x00\x00\x00\x05false\x00\x00\x00\x0ABLOCKCACHE\x00\x00\x00\x04t
>                              rueh\x0FQ\xCF
>  test1,1204765,1266581233447 column=info:regioninfo, timestamp=1266609172177, value=REGION
=> {NAME => 'test1,
>                              1204765,1266581233447', STARTKEY => '1204765', ENDKEY
=> '1290703', ENCODED => 13
>                              73493090, OFFLINE => true, SPLIT => true, TABLE =>
{{NAME => 'test1', FAMILIES =>
>                               [{NAME => 'actions', VERSIONS => '3', COMPRESSION
=> 'NONE', TTL => '2147483647'
>                              , BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE
=> 'true'}]}}
>  test1,1204765,1266581233447 column=info:server, timestamp=1266604768670, value=10.129.68.213:60020
>  test1,1204765,1266581233447 column=info:serverstartcode, timestamp=1266604768670, value=1266562597511
>  test1,1204765,1266581233447 column=info:splitA, timestamp=1266609172177, value=\x00\x071226169\x00\x00\x00\x0
>                              1\x26\xE7\xCA,\x7D\x1Btest1,1204765,1266609171581\x00\x071204765\x00\x00\x00\x05\
>                              x05test1\x00\x00\x00\x00\x00\x02\x00\x00\x00\x07IS_ROOT\x00\x00\x00\x05false\x00\
>                              x00\x00\x07IS_META\x00\x00\x00\x05false\x00\x00\x00\x01\x07\x07actions\x00\x00\x0
>                              0\x07\x00\x00\x00\x0BBLOOMFILTER\x00\x00\x00\x05false\x00\x00\x00\x0BCOMPRESSION\
>                              x00\x00\x00\x04NONE\x00\x00\x00\x08VERSIONS\x00\x00\x00\x013\x00\x00\x00\x03TTL\x
>                              00\x00\x00\x0A2147483647\x00\x00\x00\x09BLOCKSIZE\x00\x00\x00\x0565536\x00\x00\x0
>                              0\x09IN_MEMORY\x00\x00\x00\x05false\x00\x00\x00\x0ABLOCKCACHE\x00\x00\x00\x04true
>                              \xB9\xBD\xFEO
>  test1,1204765,1266581233447 column=info:splitB, timestamp=1266609172177, value=\x00\x071290703\x00\x00\x00\x0
>                              1\x26\xE7\xCA,\x7D\x1Btest1,1226169,1266609171581\x00\x071226169\x00\x00\x00\x05\
>                              x05test1\x00\x00\x00\x00\x00\x02\x00\x00\x00\x07IS_ROOT\x00\x00\x00\x05false\x00\
>                              x00\x00\x07IS_META\x00\x00\x00\x05false\x00\x00\x00\x01\x07\x07actions\x00\x00\x0
>                              0\x07\x00\x00\x00\x0BBLOOMFILTER\x00\x00\x00\x05false\x00\x00\x00\x0BCOMPRESSION\
>                              x00\x00\x00\x04NONE\x00\x00\x00\x08VERSIONS\x00\x00\x00\x013\x00\x00\x00\x03TTL\x
>                              00\x00\x00\x0A2147483647\x00\x00\x00\x09BLOCKSIZE\x00\x00\x00\x0565536\x00\x00\x0
>                              0\x09IN_MEMORY\x00\x00\x00\x05false\x00\x00\x00\x0ABLOCKCACHE\x00\x00\x00\x04true
>                              \xE1\xDF\xF8p
>  test1,1204765,1266609171581 column=info:regioninfo, timestamp=1266609172212, value=REGION
=> {NAME => 'test1,
>                              1204765,1266609171581', STARTKEY => '1204765', ENDKEY
=> '1226169', ENCODED => 21
>                              34878372, TABLE => {{NAME => 'test1', FAMILIES =>
[{NAME => 'actions', VERSIONS =
>                              > '3', COMPRESSION => 'NONE', TTL => '2147483647',
BLOCKSIZE => '65536', IN_MEMOR
>                              Y => 'false', BLOCKCACHE => 'true'}]}}
> {code}

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