Re: [Evolution-hackers] online/offline in e-d-s

[David Malcolm <dmalcolm redhat com>]

On Sun, 2004-11-07 at 21:29 -0700, Sivaiah Nallagatla wrote:
> Hi,
> 
> I am looking at supporting online/offline modes in e-d-s for evolution
> 2.2 release. Currently we have offline support only in mailer and the
> mechansim for switching between modes is by clicking on a widget. We
> want to listen to a desktop wide offline setting if possible in this
> release. That may be using  a gconf setting or dbus notification,
> currently nothing exists as far as i know. There has been discussions
> on d-d-l about gnome wide offline
> http://mail.gnome.org/archives/desktop-devel-list/2004-July/msg00111.html, 
> but not sure how far it is gone. The idea is to make  e-d-s  listen to
> this setting and  put all the backends in offline mode  and inform all
> backend  clients about the change in the state,  instead of evolution
> setting the modes on the backend using ECal or EBook apis.
> 
> I am describing what i am planning to do below . Please give your
> suggestions  comments , betters way to do it , or tell me if what i am
> thinking   just not going to work :-)
> 
> I am planning to implement a eds-offline-listner which listens to a
> gconf key to get to know of online/offline changes (this gconf will a
> desktop wide one if one gets implemented or if we resort to using some
> gui element in evolution to set online/offline modes , it will be a
> gconf key installed by e-d-s). This listner will be instantiated in

So is online/offline a per-user property? a per-machine property? Both?

GConf is for per-user preferences.  If I've got an NFS-mounted home
directory shared between several machines, each sharing the same GConf
database, do the machines have to go online/offline simultaneously when
the state changes?

Would it be better to do this using the D-Bus session bus?

> e-d-s main function (server.c). Whenever there is a change in gconf
> setting,  this listner will set the online/offline modes (dependning
> upon the setting value) on e-data-cal-factory and e-data-book-factory by
> calling methods like e_data_(cal/book)_factory_set_backends_mode. Here
> we can just set mode on the cal and address book factories created by
> e-d-s or we can query bonobo to get references of all cal/book factories
> created by other processes like exchange connector and set on all of
> them. Factories can set the mode on the backends which they have created
> so far by calling e_(cal/book)_backend_set_mode on the backends. It also
>  stores the mode in it so that it can set it on the new backends  that
> can be created later.  Each backend does different things in its methods
> implementations depending on the mode that has been set. For example
> _open methods does not try to login if mode is offline , they just load
> the items from the cache and respond to the queiries from the cache if
> one exists.  If mode is online they login to server. If the  folder
> which the backend is loading is marked for offline usuage, backend has
> to cache the conents on the file system (using e-cal-backend-cache and
> e-book-backend-cache) and install timeout handlers to get updates from
> the server periodically etc. 
> 
>  
> When a offline mode is set on the backend it has to release all the
> connects it has with server and infom all of its clients (ECal and
> EBook) about the change in the online/offlien state using
> e_(cal/book)_backend_notify_mode. If a backend has to behave readonly
> way in offline mode it has to inform all the clients about the change in
> its writable state  using e_(cal/book)_notify_writable.  There will be
> methods like e_(cal/book)_is_offline and e_(cal/book)_is_writable to
> know about the mode and read only state of clients. Using this methods
> clients can disbale the ui bits to prevent create/modify/delete
> operation on read only calendars/books in offline mode. 
> 
> 
> Evolution need to have  a account level setting to mark all the
> (mail/contacts/calendar) folders for offline usuage and also per folder
> level setting to mark per offline usuage. e-d-s caches contents of only
> those folders which are marked for offline. Other folders can not be
> user in offline mode.  
> 
> 
> I think currently downloading items for offline usage happens actaully
> when user switches to offline mode in case of mailer. Is it possible to
> download them in the background when user works in online mode in
> mailer ? Or even e-d-s should download only user chooses to go offline
> mode ? The second approach poses problems if we want to listen to
> desktop wide offline setting as applications may get notified of change
> in the setting when only after network is disconnected and there may not
> be any (or enought) time to download the items for caching).
> 
> 
> I have tried this idea to an extent in eds-offline-branch, i have added
> methods on necessary methods on backend factory and backend classes. I
> have changed the idl files to add new methods to notify cleints about
> mode and writable state changes of the backends. Groupwise address book
> backends and calendar backends , webcal backend has been modified to
> take care of the online/offline modes. Things seem to work so far 
> 
> There is a problem related to authenitcation when user starts evolution
> in offline mode and then switches to online mode. Now backends need to
> authenicate to servers but they do not have access to passwords.  Since
> all the backends are already loaded in offline mode, evolution won't
> call open methods on the backend again with passowrds. I am stil
> thinking what to do here. 
> 
> Siva
> 
> 
> 
> 
> 
> 
> 
> 
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