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https://issues.apache.org/jira/browse/HADOOP-15691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16622516#comment-16622516
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Wei-Chiu Chuang commented on HADOOP-15691:
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Thanks Steve for the work. I skimmed through the patch and I think it makes
perfect sense. It'll also make some Hadoop internal implementation much cleaner.
Just a few comments
# 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.
# Instead of defining the capabilities in StreamCapabilities.java, why not
create a PathCapabilities class for these capability definitions?
# Are these capabilities well defined somewhere? I am not a file system guy so
I am not sure if people interpret these capabilities differently.
> 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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