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https://issues.apache.org/jira/browse/HADOOP-9937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13764927#comment-13764927
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Shinichi Yamashita commented on HADOOP-9937:
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In ShellBasedUnixGroupsMapping, I think that I should reduce the execution
number of times of OS command.
I am concerned about the influence (e.g. memory) by forking OS process (id) at
the same time than speedup.
I think that it should improve calling of {{Groups#getGroups}}.
> Improvement of the group information refer frequency
> ----------------------------------------------------
>
> Key: HADOOP-9937
> URL: https://issues.apache.org/jira/browse/HADOOP-9937
> Project: Hadoop Common
> Issue Type: Improvement
> Components: security
> Affects Versions: 3.0.0
> Reporter: Shinichi Yamashita
> Priority: Minor
> Attachments: namenode-threaddump.txt
>
>
> The node (e.g. NameNode, ResourceManager) uses UGI.getGroupNames() now to get
> the information of the user's group who accessed it.
> In UGI.getGroupsNames(), synchronized is declared, but UGI instance by
> various methods each time and the node get different lock in getGroupName().
> For example, when cache time limit in userToGroupsMap of Groups expired and
> the node accepts many requests at the same time, each refers for group
> information in id command or JNI.
> To improve the refer frequency of the group information, it should change
> about synchronization.
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