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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8852) DelegationTokenRenewer should be Singleton
Date Thu, 04 Oct 2012 14:43:48 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13469413#comment-13469413

Daryn Sharp commented on HADOOP-8852:

You raise good points and I've been wary of this class for awhile.  Before critiquing the
patch, I now question the very existence of {{DelegationTokenRenewer}}. Here's why:

Like all hdfs filesystems, a valid tgt is required obtain a token from the NN.  This calls
into question the entire need for these filesystems to implicitly obtain a token.  If you
can get a token, you don't need a token!

The api of this class also cannot handle multi-token filesystems so its not generic enough
to be of general utility.  Furthermore, token renewal is correctly handled within jobs so
there's no need for a filesystem to internally renew.  One could make the case for a more
generalized renewal outside of yarn, but that would be another jira.

My recommendation is delete the class and all the logic in the filesystems that use it.
> DelegationTokenRenewer should be Singleton
> ------------------------------------------
>                 Key: HADOOP-8852
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8852
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 2.0.0-alpha
>            Reporter: Tom White
>            Assignee: Karthik Kambatla
>         Attachments: hadoop-8852.patch, hadoop-8852.patch, hadoop-8852-v1.patch
> Updated description:
> DelegationTokenRenewer should be Singleton - the instance and renewer threads should
be created/started lazily. The filesystems using the renewer shouldn't need to explicity start/stop
the renewer, and only register/de-register for token renewal.
> Original issue:
> HftpFileSystem and WebHdfsFileSystem should stop the DelegationTokenRenewer thread when
they are closed. 

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