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