Starting the kdbus discussions

[Kevin Krammer]

On Thursday, 2014-01-02, 15:34:00, Lennart Poettering wrote:
> On Thu, 02.01.14 15:25, Kevin Krammer (krammer at kde.org) wrote:
> > On Thursday, 2014-01-02, 14:42:47, Kay Sievers wrote:
> > > On Thu, Jan 2, 2014 at 2:12 PM, Kevin Krammer <krammer at kde.org> wrote:
> > > > On Thursday, 2014-01-02, 02:03:29, Lennart Poettering wrote:
> > > >> Coming back to the original question (or what I think the question
> > > >> was):
> > > >> I figure the trusted/untrusted thing is also something that would
> > > >> translate to whether people should ship unit files or dbus1 service
> > > >> activation files. (That all said, thinking about it, maybe we should
> > > >> just drop the requirement for native unit files or the user bus, and
> > > >> just keep it in for the system bus).
> > > > 
> > > > I think that would be nice, though my understanding from your other
> > > > reply
> > > > is that dbus-daemon will handle that as usual anyway, at least for the
> > > > not too distant future.
> > > 
> > > On systemd systems, the current "session bus" will be replaced by one
> > > "user bus" per user. All sessions will share the same bus of the user.
> > > That bus will be provided by the "systemd --user" instance.
> > > 
> > > There will be no dbus-daemon running or be used by default. The system
> > > bus and the user bus are both created by the systemd binary which also
> > > spawns the and manages the services.
> > 
> > Sorry, I am confused now.
> 
> Kay just tried to describe an another facet of the system after a
> desktop environment adopted systemd as a service manager: we try to
> shift the focus from a session bus to a user bus. This of course is
> another politically senstive thing since some people are strongly bound
> to the idea that multiple local session of the same user should work. We
> kinda put an end to that.

Right. I wasn't confused by the user bus vs session bus terminology, but by 
the contradiction of what you said "dbus-daemon not going away anytime soon 
for apps" and what Kay said "no dbus-daemon anywhere on systems that use 
kdbus".

So I take it that what Kay was referring to was the distant future outlook 
while you were addressing the short and medium term situation, correct?

Big fan of user bus idea btw :)

> > This seems to contradict what Lennart wrote earlier today: "Our primary
> > focus for now is the system bus, and dbus-daemon can continue to be used
> > for the session bus, even on a system that uses kdbus for the system
> > bus."
> Yes, this is correct, however as soon as kdbus and hence systemd is
> adopted as service manager by the desktops this also means that the
> desktops need to deal with the shift from a session to a user bus.

Different story though and I don't expect any big problems there.

> The shift is smaller than it might appear I figure, as we simply will
> redirect all session traffic to the user bus.

Right, something like that.
Alternatively dbus-daemon could still be allowed to run a session bus. Most 
application developers will switch to user bus because that is what they are 
expecting anyway and the odd apps that are session sensitive would still run 
unchanged.

> > Right now any application using its services can just make the D-Bus calls
> > and dbus-daemon will launch it if necessary.
> > 
> > It will either be necessary that this continues to work or that some end
> > user retrievable log or end user runnable diagnostic tool can identify
> > that FooContacts has a .service file but now needs a
> > whatever-is-needed-now-file.
> Whatever happens we will certainly make sure that unmodified apps will
> continue to work the way they currently do (though possibly are talking
> on the user bus rather than the session bus, but they shouldn't really
> notice the difference).

Great!
My concern was hard to diagnose situations because of some lower level changes 
that might even vary between systems. User support nightmare.

Cheers,
Kevin

-- 
Kevin Krammer, KDE developer, xdg-utils developer
KDE user support, developer mentoring
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