[Mageia-dev] How broken are RPM dependencies allowed to be?

[Dan Fandrich]

On Wed, Dec 14, 2011 at 11:30:33AM +0000, Pascal Terjan wrote:
> On Wed, Dec 14, 2011 at 09:14, Dan Fandrich <dan at coneharvesters.com> wrote:
> > I can understand that my particular case is unsupported, but I described
> > a different, supported, scenario that would also fail due to this problem.
> > To reiterate, a distribution upgrade from 1 to 2 (once it's finalized)
> > could involve urpmi first upgrading the perl-dependent package but avoid
> > installing the new perl itself until the end of the upgrade, which could be
> > hours or (if interrupted) days later.
> 
> During an upgrade urpmi starts by updating what it uses (perl, rpm,
> few other things, itself) and then restarts.

That has nothing to do with the problem in general. This same issue could
occur with any package that relies on a newer library (even just a newer
point version) but without mentioning that newer library version as a
versioned require. That's the more general issue of which my perl-using
example was but one example.

> > During the entirety of that time,
> > that package would be unusable. If that package happened to be a key CGI
> > script for a web site, the entire site would be down for that entire time.
> 
> That would not be prevented. The result would be that you need to
> install thousands of packages in the same transaction as they are all
> required by each other, and nothing would prevent your CGI from being
> at the end of the transaction which will happen hours or days later.

All packages are not required by each other. On my system, 13% of packages
are leaves that nothing depends on. 15% depend on nothing other than
glibc, libstdc++ or bash. Another 14% have a single other dependency, in
most cases a tightly-coupled library built from the same source code. So
trying to argue that a transaction must install thousands of packages is
specious.  And RPM's installation sequence is designed to minimize the
window when software is unusable during an upgrade.

>>> Dan