Anyone who’s been around WordPress for a “Digg effect” or other massive influx of traffic knows that it can be a real problem. From a technical standpoint, the problem is that PHP is entirely loaded into memory for every pageload. That includes the 99% of PHP that is not being used to actually render the page.
On low traffic sites, this problem is not necessarily noticed. It doesn’t have a huge impact. However when there are hundreds of requests hitting a server in a single second, that kind of overhead builds up very fast.
There are solutions to this sort of thing and depending on what the scale of the environment is, some might be more excessive than necessary. The WP Super Cache plugin is a quick solution that will cause pages loaded on WordPress to be cached meaning that if subsequent page loads can pul the HTML from the cache without having to load the overhead of PHP as well, everyone wins. On the more extreme end, server configurations can be made to send requests for different types of content (for instance, images) to specialized servers optimized for that content type.
Very geeky stuff. It’s important to note that WordPress gets a black eye all the time for it’s caching mechanisms and ability to handle the load of a “Digg effect”, etc. In fact, Instapundit Glenn Reynolds is the latest to take a stinging swipe at WordPress and trust me when I say, we heard it loud and clear.
At b5media (where I’ll be leaving as the Director of Technology soon), we’ve had to deal with this as well and have managed to develop really sound solutions to some of these problems. However, for WordPress as a whole, it is a well recognized problem that not everyone can solve by following in our footsteps (or WordPress.com footsteps).
We’re going to do what we can to help solve this problem once and for all as two of our developers, Mark Jaquith and Brian Layman will be mentoring a Google Summer of Code intern to develop a robust caching engine for WordPress. We hope that this exercise will result in a more reliable (and sane!) caching mechanism.
Integrated Caching Solutions will improve WordPress’s speed and reliablity out of the box and allow people to “Digg Proof” their sites without the struggle of installing plugins on a site that is virtually unreachable. (Source: WordPress Google Summer of Code 2008)
Glenn, I hope that the work that Mark, Brian and our intern will be doing will improve the WordPress problem. In the meantime, let me know if I can help you with anything (though I believe you are using Movable Type). It is a known issue and it’s one that needs to be solved and hopefully some steps can be made toward that this summer.