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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10351) LoadBalancer changes for supporting region replicas
Date Fri, 21 Feb 2014 22:27:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13908907#comment-13908907
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Devaraj Das commented on HBASE-10351:
-------------------------------------

Other than the point Sergey raised about putting some comments in the code around the array
manipulations, and maybe breaking the manipulations into smaller methods, it looks good to
me.
The one issue that is there I think is that the test (TestMasterOperationsForReplicas) may
be flaky (the part where retain assignments is set to true). The reason being, that in the
retainAssignment there is max iterations for choosing the server to place the region in but
that may not be correct location given the replicas. I think it's fine to leave the balancer's
assign methods as you currently have it (eventually the balancer.balance will fix it), but
modify the test to be able to handle that.
Another minor nit is that in roundRobinAssignment, we could land up in the catch-all anytime
we have numReplicas > numRegionServers. The comment in the catch-all code should be updated.
The refactor to do with introducing the Action class is good!

> LoadBalancer changes for supporting region replicas
> ---------------------------------------------------
>
>                 Key: HBASE-10351
>                 URL: https://issues.apache.org/jira/browse/HBASE-10351
>             Project: HBase
>          Issue Type: Sub-task
>          Components: master
>    Affects Versions: 0.99.0
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>         Attachments: hbase-10351_v0.patch, hbase-10351_v1.patch, hbase-10351_v3.patch
>
>
> LoadBalancer has to be aware of and enforce placement of region replicas so that the
replicas are not co-hosted in the same server, host or rack. This will ensure that the region
is highly available during process / host / rack failover. 



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