[rfc] move activation to a helper process

[Havoc Pennington]

John (J5) Palmieri wrote:
> I would rather not have the bus tied to the .service file and instead
> leave that as an implementation detail for the daemon (perhaps with some
> standard behind it).  The reason I say this is on OLPC we might want to
> make our own daemon which forks and loads python files to avoid the
> overhead of loading another instance of python.
> 
> The daemon itself should cache service files the way D-Bus does now.
> 

I don't think this is related to this patch, though. The helper is an 
implementation detail of the bus daemon, it is not any kind of public 
interface (OLPC would not for example want to provide a replacement 
helper, or at least there's certainly no provision in this patch to 
enable that).

If we want to make activation pluggable I'd suggest that we do something 
like: apps can own the org.freedesktop.DBus.ServiceFactory bus name, and 
if that name is owned the bus asks it to launch stuff either before or 
after it looks at .service files.

This is probably fairly questionable on the system bus, but then having 
the system bus spawning python stuff seems avoidable.

Havoc