Shane Hathaway wrote:
Hi all,

I'm trying to get a handle on Zope 3. I plan to take a bunch of Zope 3 modules and combine them in a new way. The goal is to create for myself a comfortable working environment that lets me run simple code in a small mod_wsgi environment with easy reloading and no ZODB initially.

To achieve this, I need to understand what's going on in the Zope 3 code base. While the code itself is easy to understand, there are many comments in the code that suggest changes are coming soon. Please help me figure out what is meant by these comments.

The first cryptic comment comes from zope.component. The _api module starts with this gem:

# SiteManager API. This needs to get deprecated eventually.

I think this meant to say that the word "Site Manager" has been deprecated. Nowadays we just say component registry. In theory. I think we just found that renaming things isn't worth all the trouble.

But... um... everything in the module uses getSiteManager(). The whole component foundation is built on it. When is it going to be replaced? With what? By whom?

I think the comment can go. It's the opposite of useful right now.

I'm assuming for the moment that the comment is a lie, and that getSiteManager() is not going away, since otherwise I have no foundation to build upon.

Yup.

I think I want to use a threading.local as my site manager. That way, I can use a different configuration for each WSGI app even if several apps run in different threads of a single Python interpreter. It looks like the zope.app.component.hooks module does something like what I want, but that module is complicated and lacks comments in the places that matter, so I'm not quite sure what it accomplishes. I'll add comments to that module if anyone can explain it fully.

zope.component.getSiteManager() is a "hooked" function (using zope.hookable). That means it can be replaced by some other implementation. zope.app.component.hooks makes use of that. It replaces zope.component.getSiteManager() with an implementation that looks up a thread local variable (SiteInfo). This replacement is done in the setHooks() function which is called some time during Zope startup.

That led me to the zope.thread module, which is apparently deprecated already, yet zope.app.component still depends on it. Is that an hysterical accident?

As said previously, zope.thread.local is just a wrapper around Python's threading.local module (which was contributed by Jim based on zope.thread.local).

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