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https://issues.apache.org/jira/browse/YARN-3021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14370811#comment-14370811
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Yongjun Zhang commented on YARN-3021:
-------------------------------------

HI Jian,

Thanks a lot for your detailed review and comments! I'm attaching rev5 to 
address all of them.

* Replaced {{new Text("HDFS_DELEGATION_TOKEN")}} with predefined constant
* About "does conf.getStrings strip off the leading or ending empty strings? if 
not, we may strip those off.", I followed {{JobSubmitter#populateTokenCache}}. 
I think it makes sense for user to not to put leading and ending empty strings.
* Removed NON_RENEWER. But still use empty renewer string instead of null. 
* I did test rev 4 earlier, and I also tested rev5 with real clusters.

Thanks for taking look at the new rev.



> YARN's delegation-token handling disallows certain trust setups to operate 
> properly over DistCp
> -----------------------------------------------------------------------------------------------
>
>                 Key: YARN-3021
>                 URL: https://issues.apache.org/jira/browse/YARN-3021
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: security
>    Affects Versions: 2.3.0
>            Reporter: Harsh J
>            Assignee: Yongjun Zhang
>         Attachments: YARN-3021.001.patch, YARN-3021.002.patch, 
> YARN-3021.003.patch, YARN-3021.004.patch, YARN-3021.patch
>
>
> Consider this scenario of 3 realms: A, B and COMMON, where A trusts COMMON, 
> and B trusts COMMON (one way trusts both), and both A and B run HDFS + YARN 
> clusters.
> Now if one logs in with a COMMON credential, and runs a job on A's YARN that 
> needs to access B's HDFS (such as a DistCp), the operation fails in the RM, 
> as it attempts a renewDelegationToken(…) synchronously during application 
> submission (to validate the managed token before it adds it to a scheduler 
> for automatic renewal). The call obviously fails cause B realm will not trust 
> A's credentials (here, the RM's principal is the renewer).
> In the 1.x JobTracker the same call is present, but it is done asynchronously 
> and once the renewal attempt failed we simply ceased to schedule any further 
> attempts of renewals, rather than fail the job immediately.
> We should change the logic such that we attempt the renewal but go easy on 
> the failure and skip the scheduling alone, rather than bubble back an error 
> to the client, failing the app submission. This way the old behaviour is 
> retained.



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