Back to the Center


Posted: 2013-12-17 14:10   |   Source   |  More posts about zope python planetpython grok

Grok the web framework was simple enough on its surface, but like an iceberg, beneath its simple surface lurked a vast codebase. This made it harder to understand Grok. We also were depending on a lot of code Grok was in fact not using. That unused code was still being loaded, distracting, and even at one point interacting with Grok to generate a security bug.

To simplify Grok we had to lose that code. This meant we couldn't go around the center of the Zope project anymore. We had to go back to the center.

Unused UI Code

When the new Zope was built, we thought we were going to create something like the old Zope, where management and even development of web applications could be done using a through-the-web UI. The new Zope therefore consisted of two parts: a selection of libraries that could be used as a web framework (or the plumbing of one, in the case of Grok), and a selection of libraries built on top of that which implemented the web UI and its content.

The old Zope and Grok had started to use the new Zope as a collection libraries, but had no need for the user interface bits.

Why did we have to include the UI code if we didn't want it? Because the Zope libraries were all tangled up. To shift the metaphor from icebergs, they were like a ball of wool after a cat's done playing with it: all tangled up.

The New Zope as Libraries

The new Zope had originally been developed as a collection of libraries all in the same repository, in a giant tree of packages. Dependencies between parts of the tree had been rather freely introduced.

Then, around 2006, we became early adopters of setuptools, and split up these libraries into a collection of independent libraries, and published them on PyPI. We learned a lot along the way on how to do proper releases and how to manage such collections of libraries.

But now we had a collection of supposedly independent libraries with a large amount of dependencies to each other. What was worse, we had circular dependencies. This meant that just about all libraries were linked to all other libraries. Grab one Zope library off PyPI, get all of them. All 80 or so...

As Chris McDonough pointed out later, what we should have done is extract the libraries one by one, and for each give a clear purpose and documentation.

But it was too late. And at least the problem was clear now.

The Cave Sprint

So the beginning of 2009 I organized a small sprint. We'd just moved house and now had the room for it. I'm now in two minds about this sprint: while we did manage to make a good first step in cleaning up dependencies, it was also the beginning of the end of my involvement in Zope. Plus cleaning up dependencies is not a very rewarding creatively, and I think sprints should inspire as well as get work done.

During this sprint we had a discussion about the Zope project itself. The original leader of the Zope project, Jim Fulton, had slowly become less involved with it, and there was a gap that needed to be filled if we wanted to drive Zope forward. It had become difficult to make decisions.

Christian Theune and Wolfgang Schnerring convinced me we should engage the Zope project more actively instead of working around it with Grok. I was convinced, as I knew that the problem of simplifying the code base needed engagement with the Zope project.

Steering Zope

So after the sprint some of us organized a Zope Steering Group, and set up a lightweight system for technical decision making so we could hopefully move Zope forward. I think it did help.

The Zope community reformulated the new Zope as a Zope Toolkit, recognizing its status as the foundation of projects like Zope 2 and Grok. We rebranded the new Zope away from the confusingly named Zope 3, which for years had implied that the new Zope was going to be a true successor to the old Zope, something that it never quite became but confused people. On the technical level at the end of the year we were able to disconnect the UI-related packages from the rest, and had left a directed acyclic graph of foundational packages, without circular dependencies.

My hope was also that new leadership could infuse new energy in the Zope project beyond just maintenance tasks like cleaning up dependencies. The web was evolving, and could we get together and do exciting new things again? The answer was no, but that will have to wait for the next article in this series.

This blog entry is a part of a series on Zope and my involvement with it. Previous. Next.

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