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https://issues.apache.org/jira/browse/HADOOP-15691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16593934#comment-16593934
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Steve Loughran commented on HADOOP-15691:
-----------------------------------------
Should be of interest to: [~sanjay.radia], [~tmarquardt], [~fabbri], [~ehiggs]
[~thomasdemoor], [~rdblue], [~arpitagarwal] [~jzhuge] [~sseth]
The goal here initially is just to let callers see if things like concat/append
work before trying, but I really want to line things up for being able to ask
if a store can do a direct write to a dest path without it being visible until
closed (so you don't need to write to a temp path & rename for that
one-operation commit), when to know that rename() doesn't do what posix
expects,
I know this breaks the idea that all filesystems should work just like HDFS,
but that is true today: we just need to be able to determine which APIs *and
semantics* are offered by specific FS instances.
> Add PathCapabilities to FS and FC to complement StreamCapabilities
> ------------------------------------------------------------------
>
> Key: HADOOP-15691
> URL: https://issues.apache.org/jira/browse/HADOOP-15691
> Project: Hadoop Common
> Issue Type: New Feature
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Major
> Attachments: HADOOP-15691-001.patch
>
>
> Add a {{PathCapabilities}} interface to both FileSystem and FileContext to
> declare the capabilities under the path of an FS
> This is needed for
> * HADOOP-15407: declare that a dest FS supports permissions
> * object stores to declare that they offer PUT-in-place alongside
> (slow-rename)
> * Anything else where the implementation semantics of an FS is so different
> caller apps would benefit from probing for the underlying semantics
> I know, we want all filesystem to work *exactly* the same. But it doesn't
> hold, especially for object stores —and to efficiently use them, callers need
> to be able to ask for specific features.
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