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https://issues.apache.org/jira/browse/HADOOP-7967?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13291215#comment-13291215
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Daryn Sharp commented on HADOOP-7967:
-------------------------------------
Certainly. I suggested in a May 8 comment to commit this minimal patch
(essentially the original patch minus the bits that have since gone in on
separate jiras), with the more extensive changes implemented on a followup
jira. The high level summary of the patch for this jira:
# I fixed the existing apis, with no semantic changes, in order to maintain
backwards-compat
# A filesystem's service always matches the token's service to prevent dups
since tokens have always been fetched if a filesystem's service is not already
in the creds
# Ability to query a fs for its set of leaf filesystems
# {{FileSystem}} obtains only missing tokens for a fs, instead of getting all
tokens and ignoring the dups
# {{ViewFileSystem}} won't get tokens for identical mountpoints
# Implicit side-effects include being able to better stack multi-token and/or
filtered filesystems
The remaining followup work is the (incompatible) api changes, auto-population
of the given credentials, and new methods like getting direct child
filesystems. This patch does not conflict or complicate the larger goal since
it only fixes the existing apis.
> Need generalized multi-token filesystem support
> -----------------------------------------------
>
> Key: HADOOP-7967
> URL: https://issues.apache.org/jira/browse/HADOOP-7967
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs, security
> Affects Versions: 0.23.1, 0.24.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Attachments: HADOOP-7967-2.patch, HADOOP-7967-3.patch,
> HADOOP-7967-4.patch, HADOOP-7967-compat.patch, HADOOP-7967.patch
>
>
> Multi-token filesystem support and its interactions with the MR
> {{TokenCache}} is problematic. The {{TokenCache}} tries to assume it has the
> knowledge to know if the tokens for a filesystem are available, which it
> can't possibly know for multi-token filesystems. Filtered filesystems are
> also problematic, such as har on viewfs. When mergeFs is implemented, it too
> will become a problem with the current implementation. Currently
> {{FileSystem}} will leak tokens even when some tokens are already present.
> The decision for token acquisition, and which tokens, should be pushed all
> the way down into the {{FileSystem}} level. The {{TokenCache}} should be
> ignorant and simply request tokens from each {{FileSystem}}.
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