Bug#998062: Please change default dbus implementation to dbus-broker

[Luca Boccassi]

On Fri, 2021-10-29 at 13:14 +0100, Luca Boccassi wrote:
> retitle -1 Allow using dbus-broker if the user installed it
> 
> On Fri, 2021-10-29 at 12:11 +0200, Michael Biebl wrote:
> > Package: at-spi2-core
> > Version: 2.42.0-1
> > Severity: wishlist
> > Tags: patch
> > X-Debbugs-Cc: bluca at debian.org, smcv at debian.org
> > 
> > Hi,
> > 
> > I currently have dbus-broker installed and enabled:
> > 
> > michael at pluto:~$ apt-cache policy dbus-broker
> > dbus-broker:
> >   Installed: 29-2
> >   Candidate: 29-2
> >   Version table:
> >  *** 29-2 500
> >         500 http://ftp.debian.org/debian sid/main amd64 Packages
> >         100 /var/lib/dpkg/status
> > michael at pluto:~$ systemctl status dbus.service
> > * dbus-broker.service - D-Bus System Message Bus
> >      Loaded: loaded (/lib/systemd/system/dbus-broker.service;
> > enabled; vendor preset: enabled)
> >      Active: active (running) since Fri 2021-10-29 10:58:51 CEST;
> > 13min ago
> > TriggeredBy: * dbus.socket
> >        Docs: man:dbus-broker-launch(1)
> >    Main PID: 591 (dbus-broker-lau)
> >       Tasks: 2 (limit: 19028)
> >      Memory: 5.8M
> >         CPU: 622ms
> >      CGroup: /system.slice/dbus-broker.service
> >              |-591 /usr/bin/dbus-broker-launch --scope system --audit
> >              `-596 dbus-broker --log 4 --controller 9 --machine-id
> > 567a68a5c2672114bcf5192d00000008 --max-bytes 536870912 --max-fds >
> > 
> > Oct 29 10:58:51 pluto systemd[1]: Starting D-Bus System Message
> > Bus...
> > Oct 29 10:58:51 pluto systemd[1]: Started D-Bus System Message Bus.
> > Oct 29 10:58:51 pluto dbus-broker-launch[591]: AppArmor enabled, but
> > not supported. Ignoring.
> > Oct 29 10:58:51 pluto dbus-broker-lau[591]: Ready
> > 
> > 
> > 
> > Yet, I still see that at-spi2-core launches a dbus-daemon instance
> > itself:
> > 
> > michael at pluto:~$ ps aux | grep dbus
> > message+     591  0.0  0.0   9744  4232 ?        Ss   10:58   0:00
> > /usr/bin/dbus-broker-launch --scope system --audit
> > message+     596  0.0  0.0   6988  4468 ?        S    10:58   0:00
> > dbus-broker --log 4 --controller 9 --machine-id
> > 567a68a5c2672114bcf5192d00000008 --max-bytes 536870912 --max-fds 4096
> > --max-matches 131072 --audit
> > michael     1643  0.0  0.0   9540  3804 ?        Ss   10:59   0:00
> > /usr/bin/dbus-broker-launch --scope user
> > michael     1711  0.0  0.0   7080  4616 ?        S    10:59   0:00
> > dbus-broker --log 4 --controller 10 --machine-id
> > 567a68a5c2672114bcf5192d00000008 --max-bytes 100000000000000 --max-
> > fds 25000000000000 --max-matches 5000000000
> > michael     2062  0.0  0.0   8024  4256 ?        S    10:59   0:00
> > /usr/bin/dbus-daemon --config-file=/usr/share/defaults/at-
> > spi2/accessibility.conf --nofork --print-address 3
> > 
> > 
> > This can be fixed by building at-spi2-core with
> > -Ddefault_bus=dbus-broker
> > This way, bus/at-spi-bus-launcher.c will first try to use dbus-broker
> > and if not available fall back to dbus-daemon.
> > 
> > I rebuilt the package with the attached patch and applied and
> > successfully tested
> > - dbus-broker installed: → dbus-broker is used
> > - dbus-broker not installed → dbus-daemon is used
> > 
> > I've CCed Simon and Luca as maintainers of dbus and dbus-broker, in
> > case
> > they have some input on this matter.
> > 
> > 
> > Regards,
> > Michael
> 
> Nice find, and for reference the fallback is here:
> 
> https://sources.debian.org/src/at-spi2-core/2.42.0-1/bus/at-spi-bus-launcher.c/?hl=405#L489
> 
> So given the default implementation is dbus-daemon it should be indeed
> safe to try first dbus-broker, and fallback to dbus-daemon if not
> installed.
> 
> I have taken the liberty to retitle slightly, to ensure it's clear that
> the request is not to force to change to dbus-broker, but simply to
> allow it to be used if the user chose it for their system.
> 
> Thanks!

MR with attribution to Michael:

https://salsa.debian.org/a11y-team/at-spi2-core/-/merge_requests/6

-- 
Kind regards,
Luca Boccassi
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