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From "Jian He (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3021) YARN's delegation-token handling disallows certain trust setups to operate properly over DistCp
Date Wed, 04 Mar 2015 03:09:05 GMT

    [ https://issues.apache.org/jira/browse/YARN-3021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14346303#comment-14346303
] 

Jian He commented on YARN-3021:
-------------------------------

bq. Consider it's also matching our future extension of introducing external renewer,
If this API is needed in the future, we can definitely do as the current patch does. My only
concern is not to add a user-facing API only used for short-term.  What I have in mind is
that, in the long term we can 
1. Change MR client to set the correct renewer for a given token, either pointing to a central
renewal service or RM itself.  Today JobClient is blindly setting the renewer of all tokens
with the local RM config which is wrong in the first place.
2. RM checks if the token renewer is itself; Renew if it is, skip renewing otherwise. 

Thinking more, how about this approach:
1. Change MR client to set null renewer for the token coming from a different cluster (meaning
no renewer for this token which is true in real scenario). This is more or less equivalent
to explicitly adding a flag to inform RM wether to renew as current patch does
2. RM implements the logic to only renew its own token. 
thoughts?



> 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
>         Attachments: YARN-3021.001.patch, YARN-3021.002.patch, YARN-3021.003.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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