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Date: Wed, 3 Dec 2014 13:01:12 +0000 (UTC)
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Subject: [jira] [Commented] (HBASE-12590) A solution for data skew in
 HBase-Mapreduce Job
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    [ https://issues.apache.org/jira/browse/HBASE-12590?page=3Dcom.atlassia=
n.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D142=
32972#comment-14232972 ]=20

Hadoop QA commented on HBASE-12590:
-----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest a=
ttachment=20
  http://issues.apache.org/jira/secure/attachment/12684872/HBase-12590-v2.p=
atch
  against master branch at commit 13a1eaec09a467153adc1ee0b46df9f457da6115.
  ATTACHMENT ID: 12684872

    {color:green}+1 @author{color}.  The patch does not contain any @author=
 tags.

    {color:green}+1 tests included{color}.  The patch appears to include 6 =
new or modified tests.

    {color:green}+1 javac{color}.  The applied patch does not increase the =
total number of javac compiler warnings.

    {color:green}+1 javac{color}.  The applied patch does not increase the =
total number of javac compiler warnings.

    {color:green}+1 javadoc{color}.  The javadoc tool did not generate any =
warning messages.

    {color:green}+1 checkstyle{color}.  The applied patch does not increase=
 the total number of checkstyle errors

    {color:green}+1 findbugs{color}.  The patch does not introduce any new =
Findbugs (version 2.0.3) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not incre=
ase the total number of release audit warnings.

    {color:green}+1 lineLengths{color}.  The patch does not introduce lines=
 longer than 100

  {color:green}+1 site{color}.  The mvn site goal succeeds with this patch.

     {color:red}-1 core tests{color}.  The patch failed these unit tests:
    =20

     {color:red}-1 core zombie tests{color}.  There are 1 zombie test(s): =
=09at org.apache.hadoop.hbase.master.balancer.TestDefaultLoadBalancer.testB=
alanceCluster(TestDefaultLoadBalancer.java:119)

Test results: https://builds.apache.org/job/PreCommit-HBASE-Build/11927//te=
stReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-hadoop-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-prefix-tree.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-examples.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-server.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-common.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-rest.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-protocol.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-client.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-thrift.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-hadoop2-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/newPatchFindbugsWarningshbase-annotations.html
Checkstyle Errors: https://builds.apache.org/job/PreCommit-HBASE-Build/1192=
7//artifact/patchprocess/checkstyle-aggregate.html

  Console output: https://builds.apache.org/job/PreCommit-HBASE-Build/11927=
//console

This message is automatically generated.

> A solution for data skew in HBase-Mapreduce Job
> -----------------------------------------------
>
>                 Key: HBASE-12590
>                 URL: https://issues.apache.org/jira/browse/HBASE-12590
>             Project: HBase
>          Issue Type: Improvement
>          Components: mapreduce
>            Reporter: Weichen Ye
>         Attachments: A Solution for Data Skew in HBase-MapReduce Job (Ver=
sion2).pdf, HBase-12590-v1.patch, HBase-12590-v2.patch
>
>
> 1, Motivation
> In production environment, data skew is a very common case. A HBase table=
 always contains a lot of small regions and several large regions. Small re=
gions waste a lot of computing resources. If we use a job to scan a table w=
ith 3000 small regions, we need a job with 3000 mappers. Large regions alwa=
ys block the job. If in a 100-region table, one region is far larger then t=
he other 99 regions. When we run a job with the table as input, 99 mappers =
will be completed very quickly, and we need to wait for the last mapper for=
 a long time.
> 2, Configuration
> Add two new configuration.=20
> hbase.mapreduce.split.autobalance =3D true means enabling the =E2=80=9Cau=
to balance=E2=80=9D in HBase-MapReduce jobs. The default value is false.=20
> hbase.mapreduce.split.targetsize =3D 1073741824 (default 1GB). The target=
 size of mapreduce splits.=20
> If a region size is large than the target size, cut the region into two s=
plit.If the sum of several small continuous region size less than the targe=
t size, combine these regions into one split.
> Example:
> In attachment
> Welcome to the Review Board.
> https://reviews.apache.org/r/28494/diff/#


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