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I recently had a discussion with Peter Wolanin about pluggable subsystems. (You can tell this is going to be an exciting entry already, can't you?) Drupal has supported a few pluggable subsystems for a long time, namely the database and cache systems. In both cases, they work on a very simple principle: Conditionally include one of two (or more) files that defines the same set of functions but with different bodies.

That's all well and good and simple, but has some very serious limitations. Most notably, because the same function name is defined twice you can never load multiple versions at the same time. That becomes a problem if you want to, say, connect to a MySQL and PostgreSQL database in the same page request. In addition, Drupal 7 is on track to include a fully introspective code registry for conditional code loading, which, based on earlier benchmarks, should be a huge performance boost. The Registry, however, assumes that all code resources (functions, classes, and interfaces) are globally unique throughout Drupal. Having a given function name defined twice will confuse the poor thing.

That is not an insurmountable problem, or even, truth be told, a difficult one. It simply requires switching from a simple include to a more formal mechanism. There are, in fact, several ways that can be done, so to further the education of the world at large (and probably embarrass myself a bit in front of other architecture buffs) I decided to write a brief survey of simple pluggable mechanisms.

A recent thread on the Drupal documentation list has brought up once again the "why don't we have a wiki on Drupal.org?" question. It comes up regularly; you can set your watch by it.

What I've never understood is why anyone would want to take a step backwards from Drupal's handbooks to a simple wiki. How would removing features and capabilities help Drupal's huge pool of documentation?

What exactly makes something "a wiki"? Let's examine:

One of the major changes in Drupal 6 (where "major" is defined as "worthy of a mention in Dries' keynote") was a new feature of the menu and theme hooks. The newly introduced "file" and "file path" keys in those hooks' respective retun arrays. allow them to define files that get included conditionally, only when needed. In theory, that should be a big performance boost; page handlers are virtually never called except for on the page they handle, so loading all of that code on every other page is a waste of CPU cycles. Of course, there is also the added cost of the extra disk hit to load that one extra file we need. Modern operating systems should do a pretty good job of caching the file load, but that may vary with the configuration.

So just how much benefit did we get from two dozen fragile patches that were a glorified cut and paste? And is it worth doing more of it? Let's benchmark it and find out.

For those who haven't really been following it, several hundred contributors, 13 months, and tens of thousands of lines of code have gone into making the only version of Drupal ever that is better than Drupal 5. So, naturally, we've released it and called it Drupal 6.

Drupal 6 boasts a boat load of new functionality, ranging from Ajaxy yumminess throughout the system to native support for OpenID to vastly enhanced multi-lingual support. Several entire subsystems have been either overhauled or totally rewritten to proivde more power, flexibility, and speed. The official press release has the complete rundown, or for the more visually inclined there's a new features screencast. For me, though, the new theming system is feature numero uno.

Marco Tabini, of php|architect magazine fame among other things, has been openly disappointed at the death of PHP 4. Not because he likes PHP 4, but because of the "OMG you're discontinuing something that everyone's still using!" argument.

I like your magazine, Marco, but I have to disagree with you on this one. :-)

The day is nearly upon us! Drupal 7 will open up developers to PHP 5 functionality when it is released next year. Already, there is talk of how, and if, to leverage PHP 5's object handling now that we don't need to deal with the weirdness of PHP 4's object model. Of course, because it's Drupal, our army of performance czars want to know just what the cost is for object handling, and especially advanced object magic like __get(), __call(), the ArrayAccess interface, and so forth.

So let's find out. :-)

So it's been a week since DrupalCon, which means I'm kinda sorta caught up enough to write about it. Hooray!

As with DrupalCon Sunnyvale, I came away with one conclusion fixed in my mind: The Community is Drupal's greatest strength. Virtually everyone upholds a strong community and open source spirit, and will gladly talk to you for hours about subjects both on topic and off, with or without beer (free or otherwise).

But enough about how cool we are. On with the rundown.