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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8852) DelegationTokenRenewer should be Singleton
Date Fri, 05 Oct 2012 00:53:48 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13469929#comment-13469929
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Karthik Kambatla commented on HADOOP-8852:
------------------------------------------

Offline discussion with ATM has helped me understand this better.

Gist for others in my position (without a clear understanding of Kerberos):
# Initial authentication is indeed expensive and involves communicating with KDC, one gets
Krb ticket upon authentication.
# Subsequent authentications with this Krb ticket are quick and don't need KDC communication.
# Hadoop tokens will not make these subsequent authentications any more efficient, because
functionally this is same as the above authentication. Tokens are useful when one doesn't
have tickets - e.g., MR tasks that execute on different nodes.

As per Daryn's suggestion, I ll go ahead and remove DelegationTokenRenewer and the relevant
logic from these filesystems.

Thanks Daryn and ATM.
                
> 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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