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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8852) DelegationTokenRenewer should be Singleton
Date Thu, 04 Oct 2012 18:11:48 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13469569#comment-13469569
] 

Karthik Kambatla commented on HADOOP-8852:
------------------------------------------

Isn't it more efficient to renew a token than to get a new token every time? I agree we can
get the first token lazily, instead of implicitly obtaining a token during {{FileSystem#init()}}

For FileSystems, is there a penalty for not renewing the tokens within the renewal period?
If there is no penalty, it might actually be detrimental to periodically renew even in the
absence of any activity.

On the other hand, if there is a penalty, I see some merit to this class. In a world with
several filesystems, MR jobs, and other external entities, this class can enable renewing
tokens sequentially in the order the systems come up for renewal. 

                
> 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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