per-user dbus

[Joerg Barfurth]

Colin Walters schrieb:
> On Tue, Nov 10, 2009 at 12:42 PM, Lennart Poettering <mzqohf at 0pointer.de> wrote:
>> Yes, I think so. I am quite confident that things like multiple SSH or
>> other kinds of remote logins will continue to exist for a long, long
>> time. I.e. there will be graphical logins and some "reduced
>> functionality" logins, such as SSH, and they will live side by
>> side.
> 
> So what's the reason we want those to have separate bus instances?  I
> certainly want, when I have a login session running, then ssh into the
> computer, to access the existing session data.   Or if my backup job
> kicks off, it'd sure be nice to pick up the gnome-keyring from my
> running desktop.
> 
> On the other hand, the only use case for having them actually be
> separate that I can think of offhand is "poor man's virt" like xnest
> testing.  And for the testing case, it's trivial to explicitly spawn a
> separate bus when you want it.
> 

I don't think you should exclude the case of two graphical sessions.

There are real desktop virt (thin client) systems (e.g. our Sun Ray) 
that have the sessions on the server. It is quite easy to obtain more 
than one graphical session that way.

Existing problems with that are not substantially different from those 
you get when running two sessions on different hosts that use a common 
networked home directory. And depend on the desktop environment you are 
using.

>> Also, I'd like to draw the distinction between session and user buses
>> also in terms of network. I.e. i still believe we should try to make
>> the session bus shared across the network, while the user bus is
>> per-machine.
> 

If the optimal scope for a session bus is everything accessing the same 
X server, would the optimal scope for a user bus be everything accessing 
the same home directory - even if that is shared or replicated over the 
network?

Maybe I don't really understand the use case yet. As for things 
mentioned in this thread:
- keyring: I probably want to share my keyring as widely as my home 
directory. But I don't want to share an unlocked key access handle to my 
keyring beyond my current session.
- PulseAudio: I don't see anything audio-specific that I want to have 
user-scope. Audio sources and sinks are generally associated with 
sessions, not users.

One thing where a user bus would really make sense is user preferences 
(i.e. dconf). But there again home directory scope is a better fit than 
user-at-host scope. For configuration both system and clients would need 
to properly distinguish sharable, local and transient settings - but 
currently we don't. That is one reason why the attempt to do networked 
gconf didn't work out too well.

- Jörg

-- 
Joerg Barfurth           phone: +49 40 23646662 / x66662
Software Engineer        mailto:joerg.barfurth at sun.com
Desktop Technology       http://reserv.ireland/twiki/bin/view/Argus/
Thin Client Software     http://www.sun.com/software/sunray/
Sun Microsystems GmbH    http://www.sun.com/software/javadesktopsystem/