WP Super Cache 0.9.8

WP Super Cache version 0.9.8 is now available. WP Super Cache is a page caching plugin for WordPress that will significantly speed up your website.

New in this release are 2 translations. The Spanish translation is by Omi and the Italian by Gianni Diurno. Please, if you use their translations, drop by their sites and leave a thank you comment! They’ve been very patient with me as I fixed gettext bugs and added new text. Both have blogged about the translations if you need to know more: Gianni, Omi.

The second major feature to go in is an “advanced” section to the debugger. This allows the plugin to check the front page every 5 minutes to make sure everything is ok. It monitors for 2 very rare problems:

1. Very very occasionally, the front page becomes a gzip file that downloads. It happened here once and I examined the cache file. There was nothing wrong with it. It was perfect. I suspect Apache and mod_rewrite got confused somehow but clearing the cache fixed it. The file generated after was exactly the same size as the old one, so no chance it got “double gzipped”.
2. In certain rare cases, where a blog has a static front page, and uses a permalink structure of /%category%/%postname%/, the wrong page may be cached as the front page. Even if your blog satisfies the two conditions above it may not suffer from this problem. I tried it on this blog for a few days and couldn’t reproduce it at all!

Nevertheless, if you’re concerned edit your wp-cache-config.php and add this line:

$wp_super_cache_advanced_debug = 1;

Reload the admin page and you’ll see this added to the debug section:

If activated, it will check your front page every 5 minutes. It’s not activated by default because these errors only happen to a small number of blogs. I’ve also noticed that WordPress seems to randomly forget to run the page checker from time to time. I debugged it and the job simply disappears from the wp-cron system! I’ve no idea why, but reloading the admin page schedules it again.
If you’re still paranoid, set your cache expiry low so at least the cache files will be recycled quickly.

Caching, Minification and CDNs

Oh, there’s a new caching plugin on the scene. W3 Total Cache works like Supercache’s half-on mode but can store to memory as well as disk (like Batcache) but also does minification and supports CDNs. I’ve been asked a few times if I’ll support those features too but I don’t see why as other plugins already have that covered (and frankly, I don’t have time to maintain such complex features):

1. WP Minify “integrates the Minify engine into your WordPress blog. Once enabled, this plugin will combine and compress JS and CSS files to improve page load time.” Thaya is very responsive and fixed a bug I reported quickly.
2. There are any number of CDN plugins for WordPress. I don’t use a CDN so I can’t recommend one but OSSDL CDN Off Linker might be worth a shot. This post on it mentions Supercache plus, a fork of this plugin.

Traffic Spikes and Benchmarks

I really should collect more of these. A few weeks ago Mark Pilgrim blogged about how his book had been republished by a 3rd party and put up for sale on Amazon. His book was published under the GNU Free Documentation License so that’s perfectly legal to do, even if a little unusual as it can be downloaded from Mark’s website and is for sale by his publisher. The blog post generated a lot of interest and a few days later I received a donation from Mark, followed by a thank you email. I’m a big fan of what Mark does, so if it had been a physical cheque or a letter I’d have framed it!
A few days after that he tweeted the following graph. Nice spike of traffic eh? His server held up fine with help from WP Super Cache.

And finally, some benchmarks, in Russian unfortunately but the pages translates well.

• WP Super Cache vs HyperCache vs W3 Total Cache vs MaxSite Cache (translation) shows Supercache doing 106154.90 requests a second, but that’s thanks to using Nginx too.
• WP Super Cache vs MaxSite Cache: Part 1 (translation) shows a tight race between Supercache and a plugin called Max Cache Lite, probably because he used Apache this time.

Summary of changes in 0.9.8:

• Added Spanish translation by Omi.
• Added Italian translation by Gianni Diurno.
• Addded advanced debug code to check front page for category problem. Enable by setting $wp_super_cache_advanced_debug to 1 in the config file.
• Fixed wordpress vs wordpress_logged_in cookie mismatch in cookie checking function.
• Correctly check if WP_CACHE is set or not. PHP is weird.
• Added wp_cache_clear_cache() to clear out cache directory.
• Only show logged in message when debugging enabled.
• Added troubleshooting point 20. PHP vs Apache user.
• Fixed problem deleting cache file.
• Don’t delete cache files when moderated comments are deleted.

PS. WordCamp Ireland is on in early March next year in picturesque Kilkenny. Here’s Sabrina’s launch post. Sign up! I’ll be going!