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From "HBase Review Board (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2468) Improvements to prewarm META cache on clients
Date Sun, 23 May 2010 22:41:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870472#action_12870472
] 

HBase Review Board commented on HBASE-2468:
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Message from: "Todd Lipcon" <todd@cloudera.com>

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This is an automatically generated e-mail. To reply, visit:
http://review.hbase.org/r/78/
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Review request for hbase.


Summary
-------

Posting review board for this JIRA on behalf of Mingjie Lai


This addresses bug HBASE-2468.
    http://issues.apache.org/jira/browse/HBASE-2468


Diffs
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  src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java 09de2ac 
  src/main/java/org/apache/hadoop/hbase/client/MetaScanner.java 3de661e 
  src/test/java/org/apache/hadoop/hbase/client/TestFromClientSide.java 95e494a 

Diff: http://review.hbase.org/r/78/diff


Testing
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Thanks,

Todd




> Improvements to prewarm META cache on clients
> ---------------------------------------------
>
>                 Key: HBASE-2468
>                 URL: https://issues.apache.org/jira/browse/HBASE-2468
>             Project: Hadoop 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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