[horde] Use of Horde with dovecot and caldav server (davical)

[Jan Schneider]

Zitat von David Brown <david at westcontrol.com>:

> Hi,
>
> Thanks for the tips.  I've a couple more questions (see under).
>
> Incidentally, do you prefer replies to go to the mailing list only,  
> or to the list and senders?  Some maillists have strong opinions  
> here, and I'd like to get it right!

The mailing list only. And thanks for asking!

> On 05/03/2012 13:59, Jan Schneider wrote:
>>
>> Zitat von David Brown <david at westcontrol.com>:
>>
>>> Hi,
>>>
>>> I don't know if this is the right place to ask about the suitability
>>> of Horde for a particular application, but if not I'd appreciate any
>>> pointers.
>>>
>>>
>>> At the moment we have a Dovecot IMAP serving our mail system, along
>>> with exim4 for outgoing email. I'm very happy with Dovecot, and have
>>> found it a fast and reliable imap server. We have about 70 mail users,
>>> using either Thunderbird or Outlook on Windows, and a few Thunderbird
>>> users on Linux, along with a number of mobile telephones of various
>>> sorts.
>>>
>>> We are looking for a number of new features:
>>>
>>> - Web interface to mail.
>>> - Centralised and shared calendars.
>>> - Centralised and shared address books.
>>> - Message filtering on the server side (for out-of-office replies, etc.)
>>>
>>>
>>> I think Horde will give me that, or at least most of it, but I'm
>>> looking for confirmation here.
>>
>> You are correct.
>>
>
> Excellent.
>
>>> I'm hoping to keep Dovecot as the backend IMAP server, but I'm open to
>>> alternatives. I would like to use caldav for the calenders, which will
>>> work fine with Thunderbird and (I think) most mobiles - and I believe
>>> there are third-party add-ons for Outlook. The most likely caldav
>>> backend would be davical.
>>
>> While Kronolith does support CalDAV as a calendar backend, it does *not*
>> support CalDAV as the default backend. This means that you will still
>> have a default SQL calendar for each user. You won't be able to manage
>> the CalDAV calendars with Kronolith either, you need to use the davical
>> interface for sharing etc.
>>
>>> Am I looking in the right place here? Or am I making life difficult
>>> for myself with this setup, and should rather be using different
>>> backend servers? I am quite happy reading technical documents, doing
>>> installations, configuring things from web interfaces or command lines
>>> and config files as required, so I don't need a hand-holding
>>> installation process. I just need a few tips to make sure I am heading
>>> in the right direction.
>>
>> Alternatively you can use WebDAV instead of CalDAV (works with
>> Lightning) and synchronize Outlook via SyncML. This way you could use
>> the default SQL backend for Kronolith and don't need additional server
>> software.
>>
>
> I can see the benefits with this - keeping a single system, with  
> user and configuration within the Horde / Kronolith framework.  But  
> will this work as well for shared calenders (with "shared" meaning  
> both "several users accessing the same calender" and "one user  
> accessing the same calender from several clients")?  In particular,  
> the aim is to get fast synchronisation without having continuous  
> polling, if that's possible. I'm not very experienced with calender  
> protocols, but what I want to avoid is that users will need to  
> manually "update" their shared calenders.

Yes, this is possible. The WebDAV protocol is not very efficient  
though. We don't support server-side CalDAV yet though.

> The worst situation is when there are lots of people sharing the  
> same calender (such as a calender for a meeting room that people can  
> book), and several of them want to put new bookings into the  
> calender.  I don't want it to be possible for one person to put a  
> booking in then upload the calender to the server, and another  
> person puts a different booking in and uploads it with the result  
> that the first change is lost.  It the uploads have to be for a  
> particular booking, which are then merged at the server, rather than  
> writing a complete full calender file at a time.  (I'm not sure I'm  
> making myself entirely clear here, but I hope you can understand my  
> point.)

Unfortunately, that's exactly what can happen when using WebDAV.  
CalDAV is much smarter, because it transfers single events, not a  
complete calendar. At least some calendar clients work around this  
though by getting a fresh calendar from the server before writing it  
back. They merge them locally, because that's not supported by the  
WebDAV protocol on the server level.
That being said, Kronolith supports resources natively, though you  
can't manage them through WebDAV.

> Additionally, I'd like changes to shared calenders to appear in all  
> places with as low a delay as practically possible.

This completely depends on the pull interval of the clients. If the  
clients use ActiveSync, there's push functionality, and the changes  
are transmitted instantly. That's not the case for WebDAV or SyncML  
clients though.

> I don't mind if Kronolith provides the backend, or just a frontend  
> (as an alternative to Outlook, Thunderbird + Lightning, Sunbird,  
> Android, etc.) connected to a different backend.
>
> Thanks for your help,
>
> David

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