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https://issues.apache.org/jira/browse/HBASE-2468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12877462#action_12877462
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HBase Review Board commented on HBASE-2468:
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Message from: "Todd Lipcon" <[email protected]>
bq. On 2010-06-10 08:53:41, Jonathan Gray wrote:
bq. > src/main/java/org/apache/hadoop/hbase/client/MetaScanner.java, line 109
bq. > <http://review.hbase.org/r/98/diff/5/?file=944#file944line109>
bq. >
bq. > Hmm, wouldn't that be Math.min then? If rowLimit = 5 and
scanner.caching = 100, we want to only do 5?
woops, yes :)
- Todd
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> Improvements to prewarm META cache on clients
> ---------------------------------------------
>
> Key: HBASE-2468
> URL: https://issues.apache.org/jira/browse/HBASE-2468
> Project: HBase
> Issue Type: Improvement
> Components: client
> Reporter: Todd Lipcon
> Assignee: Mingjie Lai
> Fix For: 0.21.0
>
> Attachments: HBASE-2468-trunk.patch
>
>
> A couple different use cases cause storms of reads to META during startup.
> For example, a large MR job will cause each map task to hit meta since it
> starts with an empty cache.
> A couple possible improvements have been proposed:
> - MR jobs could ship a copy of META for the table in the DistributedCache
> - Clients could prewarm cache by doing a large scan of all the meta for the
> table instead of random reads for each miss
> - Each miss could fetch ahead some number of rows in META
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