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

Wed Dec 14 22:44:09 CET 2011

On Wed, Dec 14, 2011 at 19:19, Dan Fandrich <dan at coneharvesters.com> wrote:
+> 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.
+
+13% of packages may be leaves that nothing depends on, but they will
+depend on something and need to be updated at the same time that what
+they depend on,  so this is not relevant.
+
+Then you list 29% not depending on much other things, meaning 71% have
+more dependencies.
+