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From "Daryn Sharp (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7933) Viewfs changes for MAPREDUCE-3529
Date Tue, 03 Jan 2012 19:10:40 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13178937#comment-13178937

Daryn Sharp commented on HADOOP-7933:

Minor: Maybe store {{mountPoints.get(i).target.targetFileSystem}} in a temp instead of invoking

I'm somewhat uneasy about adding a {{FileSystem}} dependency on {{Credentials}}.  This forces
the caller of {{getDelegationTokens(renewer,creds)}} to use a {{Credentials}} object when
ideally the caller should be able to use any object to store the tokens.  The method returns
a generic {{List}}, so maybe take a generic {{Set}}?  (It appears {{Credentials}} was selected
for convenience since that's what the MR's {{TokenCache}} uses internally?)

Would it be reasonable to populate the {{Credentials/Set}} directly?  Ie. {{ViewFileSystem}}
takes a set of existing tokens, then returns the subset of tokens for its mounts that are
not already in the existing tokens.  Then the new tokens are added right back into the existing
tokens, loop again.

I'm concerned that this appears to be creating a cross-component dependency whereby {{ViewFileSystem}}
it required to "assume" how MR's {{TokenCache}} will want the tokens keyed within its {{Credentials}}.
> Viewfs changes for MAPREDUCE-3529
> ---------------------------------
>                 Key: HADOOP-7933
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7933
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 0.23.0
>            Reporter: Siddharth Seth
>            Assignee: Siddharth Seth
>            Priority: Critical
>             Fix For: 0.23.1
>         Attachments: HADOOP-7933.txt, HADOOP7933_v1.txt, HADOOP7933_v2.txt, HDFS2665_v1.txt,
> ViewFs.getDelegationTokens returns a list of tokens for the associated namenodes. Credentials
serializes these tokens using the service name for the actual namenodes. Effectively, tokens
are not cached for viewfs (some more details in MR 3529). Affects any job which uses the TokenCache
in tasks along with viewfs (some Pig jobs).
> Talk to Jitendra about this, some options
> 1. Change Credentials.getAllTokens to return the key, instead of just a token list (associate
the viewfs canonical name with a token in credentials)
> 2. Have viewfs issue a fake token.
> Both of these would allow for a single viewfs configuration only.
> 3. An additional API in FileSystem - something like getDelegationTokens(String renewer,
Credentials credentials) - which would check the credentials object before making token requests
to the actual namenode.
> 4. An additional API in FileSystem - getCanonicalServiceNames - similar to getDelegationTokens,
which would return service names for the actual namenodes. TokenCache/Credentials can work
using this list.
> 5. have getDelegationTokens check the current UGI - and fetch tokens only if they don't
> Have a quick patch for 3, along with associated MR changes.

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