[Pkg-utopia-maintainers] Bug#495257: dbus: System bus must not be restarted during package upgrades

[Sam Morris]

On Tue, 19 Aug 2008 15:13:14 +1000, Tyson Clugg wrote:

> First up, I'm not a DBus daemon developer.
> 
> I disagree that the DBus daemon should never be restarted because the
> NetworkManager developers say so.  This is a step towards the "dark
> side" - rebooting your box after performing an upgrade is the M$ way of
> doing things.  Solid engineering can prevent this.

While I agree with this--it's not just the NetworkManager developers who 
say so. It's the upstream of dbus itself that says that, in its current 
state, the system is not designed to survive a restart of the system bus.

On the upstream bug about this, a plan has been proposed to migrate 
clients over to a way of connecting to the bus that will let them 
sensibly set up and tear down resources associated with a connection--
basically applications will get an 'on connected' and 'on disconnected' 
signal to hook into--but this won't happen in time for lenny.

> I have no idea if the following is possible, but it may be a good start
> to solving the DBus upgrade/restart puzzle:
> 
> 1. Start new DBus daemon on a new socket:
>      /var/run/dbus/system_bus_socket.new
> 
> 2. Connect to the old socket and start proxying messages between the 2
> daemons.
> 
> 3. Move the new socket over the top of the old socket:
> 
> mv /var/run/dbus/system_bus_socket.new /var/run/dbus/system_bus_socket
> 
> 4. Send message to the old daemon to force disconnection of all clients
> which should reconnect to the new daemon, once all clients disconnected
> then the old daemon shuts down.
> 
> Comments?

It's a nice idea. The issue I see is with clients that are run after the 
dbus package is upgraded needing to talk to those run before it was 
upgraded. Also there is the case where dbus is upgraded multiple times 
without restarting.

Given the current release situation, I think we should just not restart 
the bus for now.

-- 
Sam Morris
http://robots.org.uk/
 
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