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Steve Loughran <stevel@cloudera.com>
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on 25 Sep 19
HADOOP-15691 Add PathCapabilities to FileSystem and FileContext.
Contributed by Steve Loughran.

This complements the StreamCapabilities Int… Show more
HADOOP-15691 Add PathCapabilities to FileSystem and FileContext.

Contributed by Steve Loughran.

This complements the StreamCapabilities Interface by allowing applications to probe for a specific path on a specific instance of a FileSystem client

to offer a specific capability.

This is intended to allow applications to determine

* Whether a method is implemented before calling it and dealing with UnsupportedOperationException.

* Whether a specific feature is believed to be available in the remote store.

As well as a common set of capabilities defined in CommonPathCapabilities,

file systems are free to add their own capabilities, prefixed with

fs. + schema + .

The plan is to identify and document more capabilities -and for file systems which add new features, for a declaration of the availability of the feature to always be available.

Note

* The remote store is not expected to be checked for the feature;

 It is more a check of client API and the client's configuration/knowledge

 of the state of the remote system.

* Permissions are not checked.

Change-Id: I80bfebe94f4a8bdad8f3ac055495735b824968f5

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