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Date: Wed, 1 Aug 2007 13:05:52 -0700 (PDT)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-1528) HClient for multiple tables
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    [ https://issues.apache.org/jira/browse/HADOOP-1528?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12517063 ] 

Hadoop QA commented on HADOOP-1528:
-----------------------------------

+1

http://issues.apache.org/jira/secure/attachment/12362986/patch.txt applied and successfully tested against trunk revision r561885.

Test results:   http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/502/testReport/
Console output: http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/502/console

> HClient for multiple tables
> ---------------------------
>
>                 Key: HADOOP-1528
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1528
>             Project: Hadoop
>          Issue Type: Task
>          Components: contrib/hbase
>    Affects Versions: 0.15.0
>            Reporter: James Kennedy
>            Assignee: Jim Kellerman
>             Fix For: 0.15.0
>
>         Attachments: HConnection.patch, patch.txt, patch.txt, patch.txt
>
>
> I have an app that needs to access multiple HBase tables concurrently.  The current HClient can only have one table open at a time even though it caches region servers of multiple tables as they are looked up.
> This means that my application layer must open multiple HClients, one per table, perhaps caching those HClients in a pool to reuse them (and their cached table data) as appropriate.
> or
> Shall I write an HClient patch that makes the HClient  multi-table thread-safe?
> Jim's suggestion is to implement an HClient singleton (call it HClientManager?) that does the actual caching/resync of root/meta regions.  Individual HClients will still be one table, one update row at a time but will rely on the singleton for the cached table info.  We want HClients to be created and disposed as fast as possible with a minimum of meta lookups.
> Jim, what about non-root/meta regions, shouldn't they be cached and refreshed via the singleton also?  It may still be possible that a region split/resync will occur during on HClient session so does the HClientManager need to be able to notify the corresponding HClients in that event?

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