Discovering services

[Tako Schotanus]

Havoc Pennington wrote:
> Carlos Garcia Campos wrote:
>>
>> Maybe it's better to add a new method instead of using ListNames.
>
> Yeah, I think it would be better to add a method that specifically 
> lists "activatable services" or something and only includes stuff from 
> .service files (does NOT include the live/running names).
>
>> The patch is available here (against cvs head, I haven't been able to
>> get dbus from anongit):
>> http://carlosgc.linups.org/files/dbus-list-services.diff
>
> It looks pretty good, I would suggest two things:
>  - separate method from ListNames
>  - add test coverage - since ListNames itself isn't tested yet this
>    may be a little work, but it should not be too hard - if you look
>    at the tests that do an activation, you just need to ListNames after
>    the activation and be sure the activated name is listed, and call
>    your new method before the activation to be sure it's listed as
>    something activatable. You want to hook in to
>    bus/dispatch.c tests probably which will let you test the OOM
>    handling.
>
>> Another problem we have found with "atomato" is that we need to call
>> introspect method for every service, but we don't want that a service
>> which was not active, keep active after returning introspect info.
>> Is it possible to deactivate services or something like that?
>
> This is a pretty major can of worms. In general services should 
> "self-deactivate" I would say - e.g. after a timeout, or when nobody 
> is using them.
>
> But, activating everything possible seems pretty scary to begin with - 
> you might be launching apps left and right in essence. Could be 
> slooooooow and have bizarre user-visible effects such as windows opening.
But what would be the use  of asking for introspection information on a 
service that is not running yet? In a lot of cases there won't be any 
information yet (like for example the service that manages all installed 
printers) or it might in some other way be dynamically generated/determined.

So what is the usecase where you would want to know what a non-activated 
service supports?

>
> If you need this, I think we'd have to look instead at some way to 
> install the introspect information in files. But, that's a pretty 
> large project and adds a fair bit of complexity.
>

And mostl likely making introspection more difficult which might mean 
people will be even less inclined to support it.

But like I said, I'm curious what the usecase is, maybe there is a way 
(around).

Cheers,
 -Tako