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From "Tsz Wo (Nicholas), SZE (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2316) webhdfs: a complete FileSystem implementation for accessing HDFS over HTTP
Date Thu, 03 Nov 2011 19:15:32 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2316?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13143459#comment-13143459
] 

Tsz Wo (Nicholas), SZE commented on HDFS-2316:
----------------------------------------------

> FileStatus JSON payload has elements that are not part of the FileStatus interface. The
WebhdfsFileSystem client expects those elements and fails if they are not present. These elements
are: localName, isSymlink, symlink. These elements are not later used and they are lost when
creating a FileStatus in WebhdfsFileSystem. Either those elements should not be in JSON payload
(my preference) or they should not be required by the WebhdfsFileSystem.

localName is for reducing the response size.  It does not include the path prefix.  Otherwise,
the same path prefix have to be sent for each status.  It becomes a problem if the number
of statuses is huge.

symlink it in 0.23.  It is a bug that it is not used.

> delete, rename, mkdirs, setReplication JSON responses use 'boolean' as element name,
they should use the operation name as it is more descriptive.

Similar to other responses, they need a root element.  The key of the root element is the
type/class.  Then, the client can determine how to parse the JSON object by checking the key.

> FileChecksum JSON serialization is using the classname in the JSON payload, it should
not, ...

The classname is the root element.  It is required by other format such as xml.
                
> webhdfs: a complete FileSystem implementation for accessing HDFS over HTTP
> --------------------------------------------------------------------------
>
>                 Key: HDFS-2316
>                 URL: https://issues.apache.org/jira/browse/HDFS-2316
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>         Attachments: WebHdfsAPI20111020.pdf
>
>
> We current have hftp for accessing HDFS over HTTP.  However, hftp is a read-only FileSystem
and does not provide "write" accesses.
> In HDFS-2284, we propose to have webhdfs for providing a complete FileSystem implementation
for accessing HDFS over HTTP.  The is the umbrella JIRA for the tasks.

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