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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-5010) Reduce the frequency of getCurrentUser() calls from namenode
Date Thu, 18 Jul 2013 23:32:48 GMT

     [ https://issues.apache.org/jira/browse/HDFS-5010?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kihwal Lee updated HDFS-5010:
-----------------------------

    Status: Patch Available  (was: Open)
    
> Reduce the frequency of getCurrentUser() calls from namenode
> ------------------------------------------------------------
>
>                 Key: HDFS-5010
>                 URL: https://issues.apache.org/jira/browse/HDFS-5010
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode, performance
>    Affects Versions: 0.23.9, 2.1.0-beta
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>         Attachments: HDFS-5010.patch
>
>
> According to the "worst" jstack of a busy namenode I took, there were 29 BLOCKED handler
threads. All of them were blocked on the UGI class lock. Here is the breakdown:
> - 2 ensureInitialized() - from non static synchronized methods. This Jira will unblock
these.
> - 27 getCurrentUser()
> Among the 27 threads that were blocked at getCurrentUser(),
> - 18 FSPermissionChecker() - from FSNamesystem#getPermissionChecker() in most namenode
RPC methods
> - 8 BlockTokenSecretManager#generateToken() - getBlockLocations()
> - 1 NameNodeRpcServer.mkdirs
> I think FSPermissionChecker can be modified to be created with a passed in UGI. FSNamesystem
can the one already stored in RPC server by calling getRemoteUser(). This will eliminate a
bulk of getCurrentUser() calls from namenode RPC handlers. A similar change can be made to
mkdirs. Block token generation is not as straightforward. Even without it we can eliminate
majority of the calls.

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