Re: [Tracker] Refactored the src/plugins & (new) Evolution support

[Carlos Garnacho <carlos imendio com>]

Hi Philip!

Overall, great patch :), makes things quite more generic. A few comments
about it:

* What about using GTypeModule and GInterfaces for the modules? you
could have a single module that implements one interface for the indexer
and other interface for trackerd.

* Do we really have to expose TrackerIndexer? I'd rather keep that as an
internal detail, and this wouldn't work as is for external modules, we'd
have to install a bunch of headers first... If we went through
GTypeModule, modules could trigger signals that the indexer would
listen, without any need to expose it to modules.

* in src/tracker-indexer/tracker-push.c (load_modules): there's no good
reason for gotos if it's just used in a single place, just make that
return immediately if the directory couldn't be opened.

* in src/tracker-indexer/tracker-push.h: the .c file doesn't implement
tracker_push_module_[create|shutdown]

* in src/tracker-indexer/Makefile.am and src/trackerd/Makefile.am: No
need to discern between "pushi" and "pushd", since there's no naming
collision.

Cheers,
  Carlos

On mar, 2009-02-03 at 11:52 +0100, Philip Van Hoof wrote: 
> This is a new patch but with the indentation right for the two new files
> this time
>
> On Tue, 2009-02-03 at 00:40 +0100, Philip Van Hoof wrote:
> > Hi there,
> >
> > This long E-mail is also a request for a review of the attached patch,
> > Martyn.
> >
> > You can call me crazy for working on this until 24 'O clock, but I guess
> > I wanted to have it done today.
> >
> > Because Ivan Frade told me he likes the concept of letting applications
> > push in data into Tracker for many situations, we decided to refactor
> > the basis of the Evolution support that I recently finished [1].
> >
> > [1] http://live.gnome.org/Evolution/Metadata (note that this is now a
> > desktop neutral standard)
> >
> > I made this part GModule based. Meaning that you can add more such
> > "Evolution like" modules. That is also the plan. For example one module
> > for KMail and very different one for an RSS web grabber will be made
> > very soon. Perhaps we'll make other ones for other kinds of apps too.
> >
> > How it works is simple, but can get a little bit confusing to read in C.
> > I recommend reading this Vala example, as it does the same thing [2].
> >
> > [2] http://live.gnome.org/Vala/DBusClientSamples/Waiting
> >
> > In Tracker a few more things got added, like the GModule support.
> >
> > tracker-push.c in trackerd is more or less a GModule loader and at the
> > same time what the Vala example does [2] (go read it, in code it's much
> > more easy to grasp than reading this gibberish explanation!):
> >
> > -> Do a ListNames on DBus initially and if our service is among the ones
> >    we want to consume, we more or less launch the GModule's
> >    capabilities.
> >
> > -> Then we start listening for NameOwnerChanged to know when we either
> >    need to shutdown the GModule's capabilities, or when we need to
> >    launch it.
> >
> > Use-cases:
> >
> > o. Evolution is not running, trackerd starts. User now starts Evolution.
> >    The NameOwnerChanged will detect this event and will launch the
> >    GModule for Evolution.
> >
> > o. Evolution is running, trackerd starts. ListNames will find the
> >    service for us and our handler will therefore launch the GModule.
> >
> > o. We were once registered with Evolution, we're still running. But now
> >    Evolution shuts down. The NameOwnerChanged will detect this event and
> >    will disable the capabilities of the GModule for Evolution.
> >
> > Now replace Evolution with KMail if you prefer the KDE desktop. Same
> > story.
> >
> > We decided to refactor this because we want to enable Vala, Python, C#,
> > Perl, D, C++, YodaYodi++#1^^ developers to develop modules.
> >
> > This means that it's all GObject & GModule based now.
> >
> > You install a GModule that has a function that returns a GObject that
> > implements some methods in a directory A, and one in a directory B.
> >
> > Why two? Well one for the indexer and one for the daemon. The deamon is
> > for your 'things' that need to be kept alive for a long time. The
> > indexer is for your 'things' that will do a lot of DB transactions and
> > insertions.
> >
> > For for example the Evolution one the deamon one proxies RDF triples to
> > the indexer one for this reason.
> >
> > You can take a look at the existing Evolution one's Makefile.am to see
> > how to deal with that, where to install it, etc.
> >
> > Anyway, here's the patch. Please review asap as we'll need this for
> > followup tasks soon (like the RSS and the KMail support).
> >
> >
> > Thanks!
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