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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7721) Local Transactions in META
Date Wed, 06 Feb 2013 04:55:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13572169#comment-13572169
] 

Ted Yu commented on HBASE-7721:
-------------------------------

Went through half of the patch.
Locally I got this failure:
{code}
testShutdownSimpleFixup(org.apache.hadoop.hbase.regionserver.TestSplitTransactionOnCluster)
 Time elapsed: 63.304 sec  <<< FAILURE!
java.lang.AssertionError: Waiting too long for daughter regions
  at org.junit.Assert.fail(Assert.java:88)
  at org.apache.hadoop.hbase.regionserver.TestSplitTransactionOnCluster.awaitDaughters(TestSplitTransactionOnCluster.java:955)
  at org.apache.hadoop.hbase.regionserver.TestSplitTransactionOnCluster.testShutdownSimpleFixup(TestSplitTransactionOnCluster.java:374)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
{code}
                
> Local Transactions in META
> --------------------------
>
>                 Key: HBASE-7721
>                 URL: https://issues.apache.org/jira/browse/HBASE-7721
>             Project: HBase
>          Issue Type: Improvement
>          Components: Coprocessors, regionserver
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.96.0
>
>
> Thanks to Lars' local transactions patch (HBASE-5229), we can entertain the possibility
of doing local transactions within META regions.
> We need this mainly for region splits and merges. Clients scan the META concurrent to
the split/merge operations, and to prevent the clients from seeing overlapping region boundaries
or holes in META, we just through hoops. For more backgroun, see BlockingMetaScannerVisitor,
HBASE-5986, and my comments at https://reviews.apache.org/r/8716/. 
> Now, for the actual implementation options: 
>  1. As outlined in http://hadoop-hbase.blogspot.com/2012_02_01_archive.html, 
>    - We have to implement a Custom RegionSplitPolicy for the META regions to ensure that
a table's regions are always co-located in the same META region. Then we can add MultiRowMutationEndpoint
as a system level coprocessor, and use it for META operations. 
>  2. Do smt like HBASE-7716, and expose local atomic multi-row operations as a native
API.
>  3. Move META to zookeeper. Use zookeeper.multi.  
> Then we can change region split / merge logic to make use of atomic META operations.

> Thoughts, suggestions? 

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