[Zope3-dev] product installer? because of bootstrap hock

[Jim Fulton]

Roger ineichen wrote:
> Dear zope3 dev members,
> 
> If somebody is developing a product with a own service  and
 > content objects in this service.

I discourage product authors from providing new services.
Most cases where this has is done are better served by utilities.

We are activell replacing most such services with utilities.

 > They have to install the
> service first and add content objects via TTW to this service.

Or use file-system based blugins.  But, again. utilities are better.

> Or add the service via own bootstrap class.

Basically, you need to create a subscriber to DatabaseOpened events.

Because the current event system is to complex, you seem to
have to write a class.  Most subscribers are more naturally written
as functions.  The zope.app.event.function.Subscriber class makes this
easier.

> For Zope stuff, this is done in app.process.bootstrap.py

This should be more distributed than it is. There's too much
stuff in this file, and inheritence makes it more complex than it
should be.

Even if you think it makes sense to provide a new service, I question
whether it should be automagically installed by a bootstrapping process.
We do this for a few services, but not all. We happen to be getting
rid of some of the services we've done this for.

> Now somebody is developing a product there whould be nice to have
> a product installer service. 
> 
> The product installer service should do:
> 1. register services to the installer with .zcml
> 2. bootstrap the registred services
> 3. register content objects to the service (if needed)
>    or do somthing with the content objects and service.
> 4. Deinstall the product in TTW (this should deinstall 
>    the services and make shure next time we start zope
>    we don't have broken services in zodb.)
> 
> 5. Perhaps we can also install the product via TTW
> 
> I'm realy not sure if there is such a mechanism 
> allready in Zope3. Perhaps I missed somthing?
 >
 > Is anybody starting somthing like this?
 >
 > Or should I first develope a product like this
 > in Zope3 Products. That we can see it's usable?

I don't think this is necessary.  Almost all of what you describe
can be done with ZCML.

Leaving aside the fact that you need to edit products.zcml to
install a product (I'll come back to this below), your product
zcml file:

- Registeres new service types, which I discourage, and, if necessary
   provides a global service installation.

- Provides a IDatabaseOpenedEvent subscriber that does any required
   bootstrapping. Again, I think we should think long and hard about
   whether such bootstrapping is really needed.

The unstall use case in the presense of bootstrapping is an interesting
one that deserves more consideration.  I suppose that if a file-system-based
product provides bootstrapping of some sort, it should provide a facility to undo
that.  I'd rather not get into this now, though, because:

- There is a lot of other work to do, and

- I don't think that most products should do this sort of thing.

On the topic of editing products.zcml, Fred Drake is working on a prototype
for package management for Zope.  The initial goal of the effort is to support
better in-place builds of the CVS tree and Zope source and binary distributions
that are not bound by the CVS tree.  The eventual goal is to have a flexible
package-management system for file-system-based code that is part of a larger
Python packaging system.

As a part of this effort, we have decided to expant the zcml include directive
to allow file-globs in include-directive package and file attributes.  This will
allow us to have product directories that simple package installers can place files
into and remove files from, eliminating the need to edit products.zcml.

Jim

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