[wpkg-users] [Bug 121] additional EXCLUDES node for profiles

[bugzilla-daemon at bugzilla.wpkg.org]

http://bugzilla.wpkg.org/show_bug.cgi?id=121





--- Comment #3 from Rainer Meier <r.meier at wpkg.org>  2008-05-29 00:56:12 ---
Thanks for the commend. I did not read through in detail yet. But let's
construct a simple test example.

Profile x: Includes package a
Profile y: Depends on profile x but excludes acrobat-reader

Package a depends on acrobat-reader package
acrobat-reader package depends on package b

Then somebody assigns profile y to a host.

If you modify the method to collect the packages (excluding the excluded ones)
then the package tree might contain package a (but not acrobat-reader and thus
not package b). But during installation WPKG will try to apply package a which
is a part of the mandatory packages applicable for the host.

During installation of package a WPKG discovers the dependency and needs to
force installation of acrobat-reader (yes, the algorithm will do this).

Of course the install algorithm can be modified not to install acrobat-reader
in this case but this would make package a to fail its installation (dependency
missing) and thus resulting in a synchronization error during each
synchronization.

The only way out is that also package a is auto-excluded. Now the profile which
should actually only exclude "acrobat-reader" already misses 3 packages - not
to mention package eventually included by package b (dependency of
acrobat-treader) using dependency, include or chain.

And all this trouble just to assure that one package which might be heavily
integrated into the dependency tree is not applied to a system? Why should one
do this instead of simply not listing it in a generic profile applying to all
hosts? To me it looks like the 'acrobat-reader' package in this example should
be applied to only a minor number of hosts. So why not creating a 'lab-x'
profile which includes the 'base' profile (without acrobat-reader) which adds
exactly this package - and "lab-x" is assigned to a few hosts by name or IP
match only.

By experience I am sure that as soon as such a feature is available people will
start doing very very nasty things with it - just because they are simple not
aware of the "right" way to do it.

The only way I could imagine to do such a thing is that the whole dependency
tree has to be reverse-parsed for the excluded package and every package
depending on the excluded one (and the ones depending on this one...) have to
be removed from the tree. Probably packages which refer to the excluded one by
include or chain do not need to be excluded as I do not consider "include" and
"chain" as a "hard dependency" which means that a package installation is not
considered to be failed if a package which is only "included" or "chained"
fails. But it is definitely a show-stopper if a dependency cannot be installed
(either by failed installation or if it is excluded).

So an exclude specification will definitely require to remove also the packages
which depend on the excluded one from the dependency tree.

By the way - I am planning another enhancement which will allow to manually
install packages on a host. These manually added packages will be maintained on
the system (updated) even if they are not part of the profile. This would also
allow to manually add adobe-acrobat to a few of the systems - even if not
listed in _any_ profile. On all systems where it has been added manually it
will remain and will be updated if the package on the server side is updated.


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