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https://issues.apache.org/jira/browse/HADOOP-2443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12552523
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stack commented on HADOOP-2443:
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Supposition is that currently the client will not work if it does not have all
regions for a table. If so, client should work even in the case where a region
is completely missing serving all regions but the absent.
> [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
>
> 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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