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From "Mohammad Kamrul Islam (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-12621) Inconsistency/confusion around ViewFileSystem.getDelagation
Date Tue, 10 Oct 2017 04:18:01 GMT
Mohammad Kamrul Islam created HDFS-12621:
--------------------------------------------

             Summary: Inconsistency/confusion around ViewFileSystem.getDelagation 
                 Key: HDFS-12621
                 URL: https://issues.apache.org/jira/browse/HDFS-12621
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 2.7.3
            Reporter: Mohammad Kamrul Islam


*Symptom*: 
When a user invokes ViewFileSystem.getDelegationToken(String renewer), she gets a "null".
However, for any other file system, it returns a valid delegation token. For a normal user,
it is very confusing and it takes substantial time to debug/find out an alternative.

*Root Cause:*
 ViewFileSystem inherits the basic implementation from FileSystem.getDelegationToken() that
returns "_null_". The comments in the source code indicates not to use it and instead use
addDelegationTokens(). However, it works fine DistributedFileSystem. 

In short, the same client call is working for hdfs:// but not for  viewfs://. And there is
no way of end-user to identify the root cause. This also creates a lot of confusion for any
service that are supposed to work for both viewfs and hdfs.

*Possible Solution*:

_Option 1:_ Add  a LOG.warn() with reasons/alternative before returning "null" in the base
class.

_Option 2:_ As done for other FS, ViewFileSystem can override the method with a implementation
by returning the token related to fs.defaultFS. In this case, the defaultFS is something like
"viewfs://..". We need to find out the actual namenode and uses that to retrieve the delegation
token.

_Option 3:_ Open for suggestion ?

*Last note:* My hunch is : there are very few users who may be using viewfs:// with Kerberos.
Therefore, it was not being exposed earlier.

I'm working on a good solution. Please add your suggestion.



 



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