[CalendarServer-dev] Write Locks and Unmapped URLs

[Michael Rasmussen]

On Mon, 7 Apr 2008 22:11:02 +0200
Helge Heß <me at helgehess.eu> wrote:

> 
> I'm not entirely sure what your question is. Especially your point
> 1) sounds incorrect. I don't think you can get a lock on an
> umapped-URL. You would need to lock the whole collection, then fetch
> all contained names, then create the item, then unlock the
> collection. Of course thats very expensive.
> 
Maybe it is just me who has over interpreted it, but AFAIK RFC-4918 (as
of June 2007. A copy can be found in the ICalenders doc/RFC folder -
rfc4918-WebDAV Update.txt) section 7.3 writes "WebDAV provides the
ability to send a LOCK request to an unmapped URL in order to reserve
the name for use.  This is a simple way to avoid the lost-update
problem on the creation of a new resource (another way is to use
If-None-Match header specified in Section 14.26 of [RFC2616]).  It has
the side benefit of locking the new resource immediately for use of the
creator". To the best of my knowledge this indicate that the latest
specification allows this - later on it even mentions "A successful
lock request to an unmapped URL MUST result in the creation of a locked
(non-collection) resource with empty content".

> A LOCK can make sense on UPDATEs if you have a simple client which  
> can't deal well with conflicts. LOCK, GET, show, make modifications,  
> PUT, UNLOCK. This should never produce a conflict.
> 
I would think shared calendars is another strong candidate. Conflicts
with shared calendars should be a concern for the server and not the
client. IMHO.

> 
> BTW: such generic questions are better placed on the CalDAV mailing  
> list:
>    http://lists.osafoundation.org/mailman/listinfo/ietf-caldav
> 
Sorry, I will immediately request to be listed:-)

-- 
Hilsen/Regards
Michael Rasmussen

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