D-Bus interface to update multiple properties in one shot

[Tanous, Ed]

> 
> A proposal we discussed in a meet recently is to implement a new
> xyz.openbmc_project.Object.Properties D-Bus interface with a method
> called 'Update', which accepts a dictionary of property-value pairs.

I'm not really following what problem this is trying to solve.  Does the timer in networkd not work as designed?  Are we trying to remove it?  In which use cases are we seeing performance problems with multiple set calls?  Have we measured these performance impacts?

What worries me about the proposed interface is consistency.  Will we be adding the xyz.openbmc_project.Object.Properties interface as a specification to certain paths in phosphor? all paths? All object manager paths?
How will one know which paths require use of the org.freedesktop.DBus.Properties interface, and which can use the interface you've proposed?  Yes, we could do a mapper call to find out, but I'm going to negate any performance improvement we've gained.
When calling the update method, if one of the property update fails, what then?  Does the property update get partially applied, does it roll back to the old values?  I don't think there are any good catchall answers here.

This idea intrigues me, but I think in many of these cases, consistency is more important than performance.  If there's a way to keep consistency with the proposed interface _and_ get performance, then I think that this could be workable, I'm just not sure how to accomplish both.

-Ed