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https://issues.apache.org/jira/browse/HIVE-16979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16109720#comment-16109720
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Tao Li commented on HIVE-16979:
-------------------------------
[~gopalv] The original code is creating and closing a UGI instance per
metastore request, and our change is caching the UGI 24 hours after last
access. A metastore call normally takes less than a second. So 24 hours is long
enough to make sure we will not fail any ongoing metastore call. Does it answer
your question?
> Cache UGI for metastore
> -----------------------
>
> Key: HIVE-16979
> URL: https://issues.apache.org/jira/browse/HIVE-16979
> Project: Hive
> Issue Type: Improvement
> Reporter: Tao Li
> Assignee: Tao Li
> Attachments: HIVE-16979.1.patch, HIVE-16979.2.patch,
> HIVE-16979.3.patch
>
>
> FileSystem.closeAllForUGI is called per request against metastore to dispose
> UGI, which involves talking to HDFS name node and is time consuming. So the
> perf improvement would be caching and reusing the UGI.
> Per FileSystem.closeAllForUG call could take up to 20 ms as E2E latency
> against HDFS. Usually a Hive query could result in several calls against
> metastore, so we can save up to 50-100 ms per hive query.
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