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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2443) [hbase] Keep lazy cache of regions in client rather than an 'authoritative' list
Date Sat, 12 Jan 2008 22:05:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12558300#action_12558300
] 

stack commented on HADOOP-2443:
-------------------------------

Patch looks great.  Patch generates a javadoc warning... will fail on hudson: Run 'ant javadoc'
to see.  +1 after you fix the javadoc warning.

> [hbase] Keep lazy cache of regions in client rather than an 'authoritative' list
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-2443
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2443
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: contrib/hbase
>            Reporter: stack
>            Assignee: Bryan Duxbury
>             Fix For: 0.16.0
>
>         Attachments: 2443-v3.patch, 2443-v4.patch, 2443-v5.patch, 2443-v6.patch, 2443-v7.patch
>
>
> Currently, when the client gets a NotServingRegionException -- usually because its in
middle of being split or there has been a regionserver crash and region is being moved elsewhere
-- the client does a complete refresh of its cache of region locations for a table.
> Chatting with Jim about a Paul Saab upload issue from Saturday night, when tables are
big comprised of regions that are splitting fast (because of bulk upload), its unlikely a
client will ever be able to obtain a stable list of all region locations.  Given that any
update or scan requires that the list of all regions be in place before it proceeds, this
can get in the way of the client succeeding when the cluster is under load.
> Chatting, we figure that it better the client holds a lazy region cache: on NSRE, figure
out where that region has gone only and update the client-side cache for that entry only rather
than throw out all we know of a table every time.
> Hopefully this will fix the issue PS was experiencing where during intense upload, he
was unable to get/scan/hql the same table.

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