[packagekit] Questions for PK and future zypp backend development

[Boyd Timothy]

Hey everyone,

Sorry I've been absent for so long from PackageKit.  I spent a good
week doing some Tomboy hacking and then of course there was Christmas,
etc.

Anyhow, I started to get back into it this week.  I've had a couple
conversations with the Zypp team which has resulted in some questions
that I don't have the answers to and wondered if you might have them.
Some of my questions might have too obvious of answers, but I don't
have the answers because I haven't fully implemented the zypp backend
to see the results.

1) Stateless backends?

It appears that for almost every call, a new instance of zypp is
instantiated.  This may not seem too bad, but the problem is that I'm
having to do so much setup work in the first place to make even simple
calls to find out information about a package.  Some of this is being
worked on in libzypp right now, but I wondered if there's a better way
to maybe persist or reuse a currently instantiated zypp backend.  I
read through the discussion about the yum backend and it seems writing
up my own caching scheme in the zypp backend might be a bad idea...but
at least it would speed things up some and help keep state.

An example of this is when you run pk-application.  First, you search
for a package and that takes a while.  Then, you select the package,
and packagekit makes another (new) call to the zypp backend which has
to resolve the package again just to get the package description.
Maybe someone from the yum backend could explain how they're
overcoming stuff like this?

2) What is the expected behavior in PackageKit when multiple
vendors/repositories provide the same version of a package?  Do both
packages show up in the GUI?  Also, during automatic dependency
resolving, if "Package B", required by "Package A" is found from
multiple repositories, is there any logic to determine which
repository "Package B" is installed from?  Pointed out to me earlier
today in #yast involves downgrading a package and installing 32-bit
versions of some software for compatibility issues.

3) Has repository priority been considered?  You know, so I could say,
trust this repository more than that one?

4) On a GetDescription () call that would potentially result in
returning 30 packages (all of the same version) from 30 different
repositories, which one should be used for returning the description
results?

5) What is the expected behavior when "Package A" lists a specific
library as a requires, e.g., libFoo.so.4, which happens to be provided
by 30 different packages.  Which package should be returned so
libFoo.so.4 gets installed?

Cheers,

Boyd