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https://issues.apache.org/jira/browse/HADOOP-15691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16623450#comment-16623450
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Steve Loughran commented on HADOOP-15691:
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bq. Should we document a well defined capabilities? For example, we can say in
Hadoop 3.3, we define the following list of path capabilities (like
fs:snapshots) and file system implementations should support probing of these
capabilities. Right now these capabilities exist in the code, not in user docs.
bq. Let's leave to the javadocs, so that its more likely to be in sync with the
code. We can add a ref to it though in the FS docs.
bq. Instead of defining the capabilities in StreamCapabilities.java, why not
create a PathCapabilities class for these capability definitions?
I'd just added them alongside the existing ones, but yes, it makes sense. Will
do this.
bq. Are these capabilities well defined somewhere? I am not a file system guy
so I am not sure if people interpret these capabilities differently.
Not yet, we can be specific in the javadocs
> 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, HADOOP-15691-002.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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