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From "Michael Bieniosek (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-496) Expose HDFS as a WebDAV store
Date Sun, 21 Oct 2007 19:34:51 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12536531
] 

Michael Bieniosek commented on HADOOP-496:
------------------------------------------

Hey, I tried this patch out, and I noticed a few things:

1. The webdav server is hardcoded to bind to "localhost", so I changed it to bind to "0.0.0.0"
instead.  I'd prefer if clients didn't all have to run their own server: if the DNS doesn't
match, or the client doesn't want to set up hadoop and configure it, it's much easier.
2. When I actually tried to copy files out, I get a funny error in the client (on Mac OSX,
it says "There is a problem with the file and it cannot be copied").  I wish I could be more
helpful, but I don't know how to issue raw HTTP to the webdav server and there's nothing indicative
in the webdav server log.
3. If I point an ordinary browser (or wget) at the webdav server, I get a 200 with an empty
body for files that exist, and a 404 for files that don't exist.  Again, I don't know much
about webdav, but it would be nice if you could browse and download with an ordinary browser,
as in subversion.

It was nice to see this almost work, though it's not really usable for me because of problem
2.

Thanks!


> Expose HDFS as a WebDAV store
> -----------------------------
>
>                 Key: HADOOP-496
>                 URL: https://issues.apache.org/jira/browse/HADOOP-496
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Michel Tourn
>            Assignee: Enis Soztutar
>         Attachments: hadoop-webdav.zip, jetty-slide.xml, lib.webdav.tar.gz, slideusers.properties,
webdav_wip1.patch, webdav_wip2.patch
>
>
> 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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