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

[Pascal Terjan]

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.