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Date: Fri, 17 Oct 2014 16:51:35 +0000 (UTC)
From: "Esteban Gutierrez (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-12219) Cache more efficiently getAll()
 and get() in FSTableDescriptors
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    [ https://issues.apache.org/jira/browse/HBASE-12219?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14175232#comment-14175232 ] 

Esteban Gutierrez commented on HBASE-12219:
-------------------------------------------

Changed summary to reflect this no longer requires to configure a TTL to refresh the cached entries. Also aded a new property to load the HTDs at startup of the master (enabled by default) {{hbase.master.preload.tabledescriptors}}


> Cache more efficiently getAll() and get() in FSTableDescriptors
> ---------------------------------------------------------------
>
>                 Key: HBASE-12219
>                 URL: https://issues.apache.org/jira/browse/HBASE-12219
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.94.24, 0.99.1, 0.98.6.1
>            Reporter: Esteban Gutierrez
>            Assignee: Esteban Gutierrez
>              Labels: scalability
>         Attachments: HBASE-12219.v0.txt
>
>
> Currently table descriptors and tables are cached once they are accessed for the first time. Next calls to the master only require a trip to HDFS to lookup the modified time in order to reload the table descriptors if modified. However in clusters with a large number of tables or concurrent clients and this can be too aggressive to HDFS and the master causing contention to process other requests. A simple solution is to have a TTL based cached for FSTableDescriptors#getAll() and  FSTableDescriptors#TableDescriptorAndModtime() that can allow the master to process those calls faster without causing contention without having to perform a trip to HDFS for every call. to listtables() or getTableDescriptor()


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