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From "Shinichi Yamashita (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-9937) Improvement of the group information refer frequency
Date Fri, 06 Sep 2013 01:09:52 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-9937?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Shinichi Yamashita updated HADOOP-9937:
---------------------------------------

    Attachment: namenode-threaddump.txt

I attach the NameNode's thread dump. I do Thread.sleep for an investigation in UGI.getGroupsNames().
NameNode locks different UGI object in thread dump.
When update of cache by the result of id command is slow, much id command will be executed.

                
> 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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