[mythtv-users] different versions on frontend and backend

[Robert Johnston]

On 30/10/05, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> Robert Johnston wrote:
> >Incorrect. You can pass --disable-frontend and/or --disable-backend if
> >you want to make a FE-Only or BE-Only machine.
> >
> Yeah, if you don't want it to build.  Those are porting only
> options--they are /not/ valid options on Linux.  See
> http://svn.mythtv.org/trac/browser/trunk/mythtv/configure?rev=7650 lines
> 2740 and 2747--and especially lines 2741 and 2748.

These USED to be valid options to build a front-end only system (As it
seems very wasteful to have to build the whole of the backend, just to
never use it, especially on something like an XBOX-frontend, which
will NEVER be able to offer backend functionality, and building the
binaries (As well as keeping them) will only waste CPU time and HDD
space).

These were changed in Rev. 7577 to add the warnings mentioned above,
and TBH I think changing this breaks the whole "Client-Server"
functionality that Myth is supposed to be promoting, with independant
multiple frontends and multiple backends. It used to be that a backend
machine didn't require the behemoth that is X to compile, or run, but
with these dependancies, it makes what should be a small(er) program
with only the dependancies on what it needs become a huge thing that's
not efficient at all.

> >>As a matter of fact, the same applies to
> >>mythplugins--you need the same version of mythplugins as the version of
> >>mythtv.
> >>
> >>
> >That's also incorrect. MythPlugins have to be built against the same
> >version of libMyth, but you can take an old version of the plugins
> >source, as long as it's built against the same version of libMyth as
> >the MythFrontend you are wanting to load them from.
> >
> >
> Unless there are changes that break compatibility.  This includes
> incompatible changes to the myth protocol version, the DB schema
> version, the libraries used by the plugins (i.e.
> http://svn.mythtv.org/trac/ticket/531 ), and ...

In thoery, each "Plugin" should handle it's own "DB Schema", as they
should be interchangeable. IOW, MythWeather should not be touching
MythVideo's DB entries, and MythTV should not be changing MythNews'
schema.

This would mean that you could mix-and-match between Plugins/MythTV
versions, with no compatibility issues.

> And, in /all/ cases, doing so is *not* a "supported"
> configuration--which was the point I was trying to make.  Unless, of
> course, you're volunteering to provide support for all possible version
> combinations users may wish to try.

Now, I'm not going that far. But you *should* be able to compile a
backend-only system without anything breaking, as it's meant to work
independantly of any frontends that may be attached to it. Likewise
with the Frontend-Only compilation. If there is functionality that is
used in both the frontend and backend, it should be modularised so it
can be used in both independantly (Moved into libmyth, perhaps?).

Otherwise, there's not much point in having seperate front-end and
back-end programs, and the whole thing might just as well be one
massively-threaded monolithic program.

My £0.02 ($0.0355157USD)
--
Robert "Anaerin" Johnston