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Date: Wed, 12 Feb 2014 01:15:25 +0000 (UTC)
From: "Enis Soztutar (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12694457.1392114369340.27856.1392167725000@arcas>
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References: <JIRA.12694457.1392114369340@arcas>
Subject: [jira] [Commented] (HBASE-10498) Add new APIs to load balancer
 interface
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    [ https://issues.apache.org/jira/browse/HBASE-10498?page=3Dcom.atlassia=
n.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D138=
98603#comment-13898603 ]=20

Enis Soztutar commented on HBASE-10498:
---------------------------------------

bq. Can you not add a new attribute for the Stochastic LB to consider =E2=
=80=93 colocation =E2=80=93 and weight it above others rather than add API?
This is kind of the opposite of what we do for not co-locating the region r=
eplicas. The patch at HBASE-10351 adds "soft" constraints for ensuring that=
 the replicas are not co-located. I highly suggest taking a look there. How=
ever, for secondary indexing, co-locating regions should be a "hard constra=
int" I imagine.=20

Still it should be possible to implement hard constraints like co-location =
inside the core LB's, but implement the logic of deciding which regions to =
co-locate as a pluggable layer.=20

> Add new APIs to load balancer interface
> ---------------------------------------
>
>                 Key: HBASE-10498
>                 URL: https://issues.apache.org/jira/browse/HBASE-10498
>             Project: HBase
>          Issue Type: Improvement
>          Components: Balancer
>            Reporter: rajeshbabu
>            Assignee: rajeshbabu
>             Fix For: 0.98.1, 0.99.0
>
>
> If a custom load balancer required to maintain region and corresponding s=
erver locations,
> we can capture this information when we run any balancer algorithm before=
 assignment(like random,retain).
> But during master startup we will not call any balancer algorithm if a re=
gion already assinged
> During split also we open child regions first in RS and then notify to ma=
ster through zookeeper.=20
> So split regions information cannot be captured into balancer.
> Since balancer has access to master we can get the information from onlin=
e regions or region plan data structures in AM.
> But some use cases we cannot relay on this information(mainly to maintain=
 colocation of two tables regions).=20
> So it's better to add some APIs to load balancer to notify balancer when =
*region is online or offline*.
> These APIs helps a lot to maintain *regions colocation through custom loa=
d balancer* which is very important in secondary indexing.=20


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