BMC redundancy

[Andrew Jeffery]

Hi Deepak,

> So several of the existing OpenBMC apps implement specific D-Bus 
> services. What does it take to make remote D-Bus calls to such apps?
> - It doesn't look like the D-Bus spec or libdbus officially has anything 
> for D-Bus across computers. There are some good notes at 
> https://www.freedesktop.org/wiki/Software/DBusRemote/.

Applications can cannect to remote dbus servers; the --address option to dbus-daemon allows it to listen on a TCP socket and setting DBUS_SESSION_BUS_ADDRESS will point applications in the right direction. So there are probably two ways we could do this:

1. Slave BMCs connect to the master's DBus daemon, and applications namespace their objects appropriately. Multi-BMC aware applications on the master access the namespaced objects as required
2. Slave BMCs are willfully ignorant of their role, with the master connecting to the slaves' DBus daemons to form a coherent global view of the bus for its multi-BMC aware applications, which access the remote objects as required.

Given the support DBus has today it might be easier to go for 1 than for 2, if we go down this path at all.

[1] https://dbus.freedesktop.org/doc/dbus-daemon.1.html

> - There are ways to achieve this via Qt D-Bus, but it would involve some 
> amount tweaking with the D-Bus configs.
> - I'm not aware of any open/active project implementing remote D-Bus.

Here is someone's attempt at making it easier: http://gabriel.sourceforge.net/howto.html though you would struggle to say it's active given the last contribution was 2013-05-14.

> - Thoughts on doing remote D-Bus over WebSockets?

How do websockets come into the picture? Why do we need the extra complication vs normal sockets?

Cheers,

Andrew