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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12219) Cache more efficiently getAll() and get() in FSTableDescriptors
Date Sun, 02 Nov 2014 23:41:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12219?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14194092#comment-14194092
] 

Andrew Purtell commented on HBASE-12219:
----------------------------------------

The timeout setting above is a nice tip. When hunting zombies locally you can also set the
first part and second part fork modes to "always" so each test runs in its own VM, then loop
the unit test suite, watch for stragglers, then jstack. Works well because you can be sure
every stack in the dump is relevant for the hung test.  

> 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
>             Fix For: 2.0.0, 0.98.8, 0.99.2
>
>         Attachments: HBASE-12219-0.98.patch, HBASE-12219-0.98.v1.patch, HBASE-12219-0.99.addendum.patch,
HBASE-12219-0.99.patch, HBASE-12219-v1.patch, HBASE-12219-v1.patch, HBASE-12219.v0.txt, HBASE-12219.v2.patch,
HBASE-12219.v3.patch, list.png
>
>
> 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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