[Kde-pim] New feature: Hypervisor

[Volker Krause]

On Thursday 10 October 2013 12:45:09 Daniel Vrátil wrote:
> On Thursday 03 of October 2013 12:48:31 Volker Krause wrote:
> > * Resuming agents
> > 
> > The tricky part is triggering this when needed. From the discussion so far
> > we seem to have the following scenarios:
> > 
> > (1) D-Bus calls: This includes sync requests for resources or changes to
> > the agent configuration. As Dan outlined we can intercept the well-known
> > calls by the already existing redirection through akonadi_control, and
> > start the agent on demand.
> > 
> > To cover even custom interfaces (e.g. the send later agent), there's the
> > following systemd-inspired crazy idea: Before shutting down an agent we
> > "clone" it's D-Bus interface in akonadi_control, and use that for
> > on-demand
> > starting similar to the approach for well-known methods described above.
> > qdbusviewer shows you can completely introspect the interface,
> > QMetaObjectBuilder & friends allow to create custom QMetaObjects, which
> > then could be exported via D-Bus again. Needs a bit of research to see if
> > that's actually feasible, and where the limitations are, but it would be
> > a nicely generic solution to any D-Bus call :)
> 
> Sounds crazy but it has been proven to work :-) I'm just wondering, whether
> it means that the agent has to be started when Akonadi starts so that
> server can take snapshot of the DBus interface? The interface could be
> cached, but then there could be problem with interface API changes after
> update.

Starting the agent once is the save fallback, we could ask agents to install 
their D-Bus XML files to avoid even that, as an additional optimization.

For detecting API changes we could rely on the agent executable mtime, a 
version number in the desktop file, etc. None of this is perfect (interface 
could change as part of a library, you might forget to update the desktop 
file, etc), but IMHO good enough. And once we start the agent due to an 
incoming call we can update our snapshot anyway.

regards,
Volker

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