Bug#411657: Transition from sarge-etch for zope packages

[A Mennucc]

On Wed, Feb 21, 2007 at 11:12:17AM -0800, Steve Langasek wrote:
> OTOH, I also don't see why it's important to avoid
> removal of zope2.7 on upgrade, it /is/ an obsolete package from the etch
> perspective.

Because there is not a guaranteed a smooth upgrade between Zope packages,
and products therein.

Often, when people use zope , they would embed into it a  set
of products (be it custom scripts, or products downloaded from
Internet - www.zope.org has many ); in my past experience it
happens that after an upgrade of zope, those products fail to work.
(In my case, it was ExtFile, AFAICR).
The worst case scenario is that the whole zope
instance fails to start. So, you cannot even repair it easily.

For this reason it is most important that people upgrading
to Etch can still run zope2.7. If such a nightmare scenario
occours, they need to be able to run zope2.7 for as long as is
needed to upgrade all internal products and scripts.

Consider also as an example Plone: it may be the case that an old
version of Plone is incompatible with zope2.9 (I am not sure of this,
but lets pretend, for sake of example) ; so the upgrade path is
0) stop zope2.7
1) upgrade Plone to a newer version
2) start zope2.7
3) enter into the administrative interface and fire the
  "plone migration tool" to upgrade the instance to the newer Plone
4) stop zope2.7 and remove it
5) apt-get install zope2.9
6) start zope2.9 and test that the Plone site is working fine

If the Etch upgrade forces the removal of zope2.7 , then 
the whole upgrade path above is doomed.
And if the upgrade removes zope2.7 and does not permit to reinstall
it due to strange dependency conflict , then the users will be quite
mad. (I would, for once).

a.

ps: I have a zope2.7 site ; when I upgraded this machine to Etch,
 I kept Sarge in a chroot, and I am running it there :-) 
 (that is what I call a very smooth upgrade path! :-)
 as soon as a proper zope-common is in archives, I can field test
 an upgrade and let you know.

-- 
Andrea Mennucc

"The EULA sounds like it was written by a team of lawyers who want to tell 
me what I can't do, and the GPL sounds like it was written by a human 
being who wants me to know what I can do."
Anonymous,    http://www.securityfocus.com/columnists/420
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