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From "Michel Tourn (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-496) Expose HDFS as a WebDAV store
Date Wed, 30 Aug 2006 19:29:00 GMT
Expose HDFS as a WebDAV store
-----------------------------

                 Key: HADOOP-496
                 URL: http://issues.apache.org/jira/browse/HADOOP-496
             Project: Hadoop
          Issue Type: New Feature
          Components: dfs
            Reporter: Michel Tourn


WebDAV stands for Distributed Authoring and Versioning. It is a set of extensions to the HTTP
protocol that lets users collaboratively edit and manage files on a remote web server. It
is often considered as a replacement for NFS or SAMBA

HDFS (Hadoop Distributed File System) needs a friendly file system interface. DFSShell commands
are unfamiliar. Instead it is more convenient for Hadoop users to use a mountable network
drive. A friendly interface to HDFS will be used both for casual browsing of data and for
bulk import/export. 

The FUSE provider for HDFS is already available ( http://issues.apache.org/jira/browse/HADOOP-17
)  but it had scalability problems. WebDAV is a popular alternative. 

The typical licensing terms for WebDAV tools are also attractive: 
GPL for Linux client tools that Hadoop would not redistribute anyway. 
More importantly, Apache Project/Apache license for Java tools and for server components.

This allows for a tighter integration with the HDFS code base.

There are some interesting Apache projects that support WebDAV.
But these are probably too heavyweight for the needs of Hadoop:
Tomcat servlet: http://tomcat.apache.org/tomcat-4.1-doc/catalina/docs/api/org/apache/catalina/servlets/WebdavServlet.html
Slide:          http://jakarta.apache.org/slide/

Being HTTP-based and "backwards-compatible" with Web Browser clients, the WebDAV server protocol
could even be piggy-backed on the existing Web UI ports of the Hadoop name node / data nodes.
WebDAV can be hosted as (Jetty) servlets. This minimizes server code bloat and this avoids
additional network traffic between HDFS and the WebDAV server.

General Clients (read-only):
Any web browser

Linux Clients: 
Mountable GPL davfs2  http://dav.sourceforge.net/
FTP-like  GPL Cadaver http://www.webdav.org/cadaver/

Server Protocol compliance tests:
http://www.webdav.org/neon/litmus/  
A goal is for Hadoop HDFS to pass this test (minus support for Properties)

Pure Java clients:
DAV Explorer Apache lic. http://www.ics.uci.edu/~webdav/	

WebDAV also makes it convenient to add advanced features in an incremental fashion:
file locking, access control lists, hard links, symbolic links.
New WebDAV standards get accepted and more or less featured WebDAV clients exist.
core              http://www.webdav.org/specs/rfc2518.html
ACLs              http://www.webdav.org/specs/rfc3744.html
redirects "soft links" http://greenbytes.de/tech/webdav/rfc4437.html
BIND "hard links" http://www.webdav.org/bind/
quota             http://tools.ietf.org/html/rfc4331



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