Vinod Kumar Vavilapalli commented on YARN-3021:

bq. So my question is, should YARN support running a job without validating a 
token? (Though MR1 "support" this because the token renewal is asynchronous as 
Harsh pointed out). 
As I proposed in the beginning of this JIRA, if we want to do this, it has to 
be explicit in the app-submission. There are several corner cases that are 
leaking though. Even if RM successfully validates a token at app-submission, 
the remote service may be down at the time of renewal. So I think there are two 
 # Should RM validate the token by renewing at the time of app-submission?
 # Should RM fail the app if renewal fails any time during the app-execution?

Ostensibly, (1) and (2) are the same because for now check-token == renew-token 
successfully. But user can always ask us to not renew tokens explicitly at 
app-submission for whatever reason.

> YARN's delegation-token handling disallows certain trust setups to operate 
> properly
> -----------------------------------------------------------------------------------
>                 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.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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