[jira] [Updated] (HADOOP-15691) Add PathCapabilities to FS and FC to complement StreamCapabilities

["Xiaoqiao He (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-15691?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xiaoqiao He updated HADOOP-15691:
---------------------------------
    Fix Version/s: 3.2.3
                   3.2.2

Add fix version 3.2.2 + 3.2.3, Please update fix version tag in time when commit and backport, Thanks.

> 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
>             Fix For: 3.3.0, 3.2.2, 3.2.3
>
>         Attachments: HADOOP-15691-001.patch, HADOOP-15691-002.patch, HADOOP-15691-003.patch, HADOOP-15691-004.patch
>
>
> This complements the {{StreamCapabilities}} interface by allowing applications 
> to probe for a specific path on a specific instance of a {{FileSystem}}
> or {{FileContext}} offering a specific feature.
> This is intended to allow applications to determine 
> * Whether a method is implemented before calling it and dealing with
>   any subsequent 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.
> The interface may be offered by other classes too; there is no restriction here.
> 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.
> This is needed for 
> * HADOOP-14707: 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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