[Zope-dev] RE: Clarification re: Zope X3.1, 2.8

[Brian Lloyd]

> Chris wrote:
> I assume these caveats are spelled out here because Z3 
> developers don't
> want to slow down Z3 development to test/maintain Z2 compatibility.  I
> know a lot about Z2 code, but I know very little about Z3 code.  I'd
> like that to change, but it's likely that I'll just not have the
> bandwidth to make sure Z3-inside-Z2 works.  If that just means I can't
> use Z3 features but nothing else breaks, it's probably fine, but if Z3
> integration actively breaks Z2, it's likely I'll just need for some
> extended period of time to continue to use and maintain 2.7.
> 
> It'd be great if active Z3 developers could actually help make new
> releases of Z2 once Five is integrated but the above makes it 
> sound like
> a "we'll throw it over the wall and you make it work" sort of 
> thing.  If
> it's the latter, maybe as devil's advocate, I need to ask 
> what the point
> is here?
> 
> It appears there is an assumption that merging Z2 and Z3 code 
> within Z2
> itself is an unmitigated good thing, but IMHO, each is complicated
> enough in their own right that I'd personally prefer to be 
> dealing with
> one or the other at any given time and not both.  This isn't exactly
> idle whining either, I need to do this when I maintain Z4I code, and
> it's definitely not a walk in the park; it's moderately 
> difficult to do
> and also difficult find people who have the skills to help too.
> 
> Does anyone else share this skepticism or am I about to get shouted
> down? ;-)
> 
> - C

A lot of time was spent talking about these (legitimate) concerns - 
unfortunately it will probably take a little time to distill all 
of that communication to the community. But let me take a shot ;)

There are several different groups, with different goals and 
concerns, who are involved here:

  A: Z2 developers that don't care right now about Z3

  B: Z2 developers that care about Z3, but can't effectively 
     use anything Z3 related right now because it is not practical 
     or possible to switch wholesale and there is no bridge to 
     Z3 that doesn't require throwing away existing investments 
     in Z2

  C: Z3 developers that don't care about Z2 anymore, often because 
     they dont have existing investments in Z2

There are a significant and growing number of people in group B. 

At the paris sprint, we were looking for a way to:

  - Allow folks in group B to start taking advantage of (and 
    developing an interest in and contributing to!) Zope 3 
    technologies

  - Make sure that group A would not be 'forced' to do anything
    they don't want to do

  - Make sure that group C would not be 'forced' to do anything 
    they don't want to do

I feel that the approach of integrating Five into Zope officially 
does a pretty good job of meeting those goals. We added the Five 
product and a snapshot of Zope X3.0 into the core so that people 
could have a reliable baseline 'out of the box'.

That integration touched almost nothing in the Z2 code (one or 
two things that were previously done as monkey patches were 
un-monkeyed, but that's about it).

The Z3 code (and the Five code) just sits there unused unless you 
choose to use it, so Zope3 code breaking Z2 apps is not really a 
concern. But is there and available, so people can begin to plot 
their own migration paths based on their own situations.

Like other areas of Z2 (and Z3, for that matter), contributors 
tend to develop areas of expertise. A new area of expertise for 
Z2 going forward will be the Five/Z3 integration, and there will 
be a set of devs who will likely focus on that aspect. I don't 
expect that the fact that Five and Z3 integration exists will 
make life any harder for someone who focuses on purely Z2 
aspects of the core anytime soon.

So the short answer is, we tried really hard to make sure to 
take an approach where z3 integration would not actively break 
zope2 in any way or force people into any particular direction.

I *do* expect these (good) questions to recur in future Z2 
releases, as integration and ability to use Z3 technologies 
increases, but we'll have plenty of time to work those out.

For now, I think it is a huge win to make some Z3 avenues 
available to people who want to use them, without forcing 
everyone to drink the kool-aid at once ;)



Brian Lloyd        brian at zope.com
V.P. Engineering   540.361.1716              
Zope Corporation   http://www.zope.com