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https://issues.apache.org/jira/browse/HADOOP-7933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13178937#comment-13178937
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Daryn Sharp commented on HADOOP-7933:
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Minor: Maybe store {{mountPoints.get(i).target.targetFileSystem}} in a temp
instead of invoking twice?
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, 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 exist.
> Have a quick patch for 3, along with associated MR changes.
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