[systemd-devel] bus1, dbus(-daemon) and systemd

[David Herrmann]

Hey

On Sat, Oct 1, 2016 at 1:30 PM, Michael Biebl <mbiebl at gmail.com> wrote:
> Hi,
>
> I've been watching the bus1 presentation from this years systemd.conf
> (thanks a lot for the video team btw for doing a stellar job).
>
> What didn't become clear to me i, how bus1, dbus(-daemon) and systemd
> are supposed to fit together in the future.
>
> If I understood David correctly, bus1 is not meant as a drop-in
> replacement for dbus-daemon, but rather provide some simpler, lower
> level communication primitives.

Yes!

> In an earlier talk by Lennart, he mentioned that systemd will
> (re)implement dbus-daemon.
> Would this reimplmentation be based on bus1 or be a completely
> separate re-implementation *not* using bus1?

The idea of re-implementing dbus-daemon with sd-bus (in systemd) is
much older than bus1. I don't think we ever discussed it with bus1 in
mind.

> Such a hypothetical dbus-daemon replacement based on bus1, how would
> this look like and what would systemd's role be there?
>
> I would guess you already thought about that and you already have
> plans in that regard.
> Would be great if you can share them with us.

There are many issues with dbus-daemon. Some can be solved with a
simple re-implementation and fixing the known issues, others cannot.
The bus1 transport does not magically solve them, either. However, we
do have ideas how to make use of bus1 capabilities to allow direct
channels between peers, without breaking with dbus semantics.
Furthermore, we have discussed subscription-models over match-rules
that would even allow to do broadcasts/multicasts without requiring a
broker.

We are currently doing a reevaluation of our ideas and writing them
up. The intention is to get a dbus-daemon drop-in extended with
optional bus1 features.

Thanks
David