Support restarting dbus-broker about dbus-broker HOT 4 OPEN

Restarting dbus-broker is already somewhat possible, as long as you make all clients reconnect somehow, either by having the client reconnect or by restarting them. (With systemd, you just do a daemon-reexec, and then you can deal with everything else). I already do this for server upgrades, and it beats the fact that a restart of the prior dbus-daemon made my systems unusable entirely beyond a reboot.

However, not having to do that would be amazing, of course.

from dbus-broker.

I discussed this with @thom311 at devconf as well. Nice to see it's being considered.

from dbus-broker.

Just for completeness: I can see why this is handy. At the same time, this is a non-trivial extension.

In dbus-broker, we never access outside resources. The entire daemon is self-contained and fully controlled by its launcher. This makes restarting it easy (if you solve the serialization/deserialization part, which itself is a bigger effort). However, the outer part troubles me. The launcher we provide mirrors the behavior of dbus-daemon regarding configuration parsing, reloading, activation, etc. There might be circular dependencies there (like dbus-broker depending on systemd, and vice-versa), and it is not clear how such a system can be restarted in a safe way. Sure, you can just make them restart in parallel, and it will work most of the time. However, this is something I don't like being involved in. Distribution right now don't provide safe live-updated, and I feel a bit hesitant joining this unsafe area.

Long story short: Making dbus-broker restartable should be easy (in the sense of possible problems), but rather a bigger effort. Regarding the launcher, it is easy and less effort, but we would really have to mark this as "you're on your on there", if you restart across non-bugfix releases. While it will be consistent in itself, we can never guarantee consistency with outside dependencies, unless they provide a consistent restart-behavior.

from dbus-broker.

An old discussion was here: https://wiki.ubuntu.com/DbusRestart

Occasionally this issue still pops up. Usually it pops up on the client-side, like "why does NetworkManager not reconnect to the bus when restarting dbus.service". But I still think that it doesn't scale that every client handles restart of the broker. IMO the only solution can be that the broker handles it transparently.

As @dvdhrm says, probably the broker could support it, if somebody implements it. But there also seems not enough necessity/interest for anybody to step up (which is fine)...

from dbus-broker.