[Zope3-dev] Re: zope.viewlet breaking buildout?

[Jim Fulton]

On Apr 17, 2007, at 9:13 AM, David Pratt wrote:

> The pre-flight is just an idea at the moment. Buildouts present  
> constantly changing dependencies as different package releases are  
> made. I can see some buildouts getting into the one to two hundred  
> egg range. I guess from my perspective, it would be helpful to see  
> some sort of globally generated dependency output for a buildout  
> (opposed to through each package's setup or the egg info produced).

But dependencies aren't global.  Each script can have a different set  
of dependencies.  To find out what these are, look at the generated  
scripts.

It might be nice to have a tool that generates a dependency tree from  
a working set.  This tool is far more general than buildout and could  
be used, for example, with an script or interpreter generated by   
buildout.


> I'm also wanting some assurance that a buildout will run to  
> completion without fear that a recent package revision or change  
> will break it, particularly for deployment. I don't want dependency  
> issues to be a factor in killing the automation from executing  
> properly - so have been thinking about this in any case. This  
> potential exists even if the buildout has successfully run before.  
> Many thanks.

For deployment, you're better off specifying versions so you don't  
get accidental upgrades at deployment time.  buildout provides a  
number of tools for doing this, most notably:

   http://www.python.org/pypi/zc.buildout/1.0.0b23#repeatable- 
buildouts-controlling-eggs-used

For greater safety, if deployments are very important to you,  
consider building system installation packages from buildouts.  I  
create RPMs from buildouts and we then use these RPMs to deploy. I  
intend to write up how I've done this, although I haven't done so  
yet, unfortunately.

Jim

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