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!

WP Super Cache version 0.9.7 is now available. WP Super Cache is a page caching plugin for WordPress that will significantly speed up your website.

Since the last release of the plugin a number of new features have been adding, bugs fixed, and documentation updated. For a taster, here are the changes from the readme.txt:

1. Fixed problem with blogs in folders.
2. Added cache file listing and delete links to admin page.
3. Added “Newest Cached Pages” listing in sidebox.
4. Made admin page translatable. (work in progress)
5. Added “How do I make certain parts of the page stay dynamic?” to FAQ.
6. Disable supercaching when GET parameters present instead of disabling all caching. Disable on POST (as normal) and preview.
7. Fixed problem with cron job and mutex filename.
8. Warn users they must enable mobile device support if rewrite rules detected. Better detection of when to warn that .htaccess rules must be updated (no need when rewrite rules not present)
9. Use the wordpress_test_cookie in the cache key.
10. Show correct number of cache files when compression off.
11. Fixed problem with PHP safe_mode detection.
12. Various bugfixes and documentation updates. See Changelog.txt
13. Advanced: added “late init” feature so that plugin activates on “init”. Set $wp_super_cache_late_init to true in config file to use.
14. Advanced: Added “wpsupercache_404″ filter. Return true to cache 404 error pages.

If you’re upgrading and your blog is installed in a sub directory the mod_rewrite rules may not have been created correctly. You’ll know this because the timestamp on your cached pages will change on every load. If that happens, remove the Supercache rewrite rules and recreate them through the admin page.

You can list all the blog’s cache files now, ordered by generation time. From that listing you can delete individual files.

The debug function is very powerful. You can choose the level of logging. Level 1 logs errors and warnings of a serious nature. Level 5 logs them plus lots of normal functions. Here’s what level 5 logging looks like for one single request:

20:49:34 /was-the-janitor-really-in-the-fugitive/ No wp-cache file exists or user agent rejected.
20:49:35 /was-the-janitor-really-in-the-fugitive/ In WP Cache Phase 2
21:49:35 /was-the-janitor-really-in-the-fugitive/ Setting up WordPress actions
21:49:35 /was-the-janitor-really-in-the-fugitive/ Created output buffer
21:49:35 /was-the-janitor-really-in-the-fugitive/ supercache dir: /www/wp-content/cache/supercache/ocaoimh.ie/was-the-janitor-really-in-the-fugitive/
21:49:35 /was-the-janitor-really-in-the-fugitive/ Output buffer callback
21:49:35 /was-the-janitor-really-in-the-fugitive/ supercache dir: /www/wp-content/cache/supercache/ocaoimh.ie/was-the-janitor-really-in-the-fugitive/
21:49:35 /was-the-janitor-really-in-the-fugitive/ Anonymous user detected. Only creating Supercache file.
21:49:35 /was-the-janitor-really-in-the-fugitive/ Gzipping buffer.
21:49:35 /was-the-janitor-really-in-the-fugitive/ Writing non-gzipped buffer to supercache file.
21:49:35 /was-the-janitor-really-in-the-fugitive/ Writing gzipped buffer to supercache file.
21:49:35 /was-the-janitor-really-in-the-fugitive/ Renamed temp supercache file to /www/wp-content/cache/supercache/ocaoimh.ie/was-the-janitor-really-in-the-fugitive/index.html
21:49:35 /was-the-janitor-really-in-the-fugitive/ Renamed temp supercache gz file to /www/wp-content/cache/supercache/ocaoimh.ie/was-the-janitor-really-in-the-fugitive/index.html.gz
21:49:35 /was-the-janitor-really-in-the-fugitive/ Sending buffer to browser

That’s a lot of text. Keep an eye on the load on your server because logging that much data on a busy server will add extra load. Start by limiting the logging to your own IP and test with various browsers.
The error messages that are normally sent to the browser about “missing html tag”, “404 error” and “blank page” are now only shown if debugging is enabled. This will hopefully avoid problems with PHP scripts that generate Javascript.

This release adds a new “late init” feature. This is only useful in half-on mode however. This causes the plugin to create the “cache key” and display the cached page at the end of the “init” action, after all WordPress include files and plugins have been loaded. This is very useful if your application needs to interrogate the database to modify the cache key. Activate it by setting $wp_super_cache_late_init to true in the config file.

Lots to digest and new toys to try out. Hope you enjoy this new version of the plugin!

WP Super Cache version 0.9.1 is now available. WP Super Cache is a page caching plugin for WordPress that will significantly speed up your website.

Major changes under the hood in this release, and many bugfixes:

• If your blog is installed in a folder then compare the mod_rewrite rules in your .htaccess with those on the admin page. I fixed a bug in how those are generated.
• Out goes the shutdown function the plugin relied on for years (going back to the days of wp-cache), and in comes plain old output buffering on it’s own.
• If you’ve had problems clearing the cache on your blog it could be because wp-cron isn’t firing. I’ve added checks for that. Joost helped me debug that and he blogged about it too. You’ll get a nice warning message if those checks fail.
• If after all that, your cache still doesn’t clear, add $wp_cache_shutdown_gc = 1; to wp-content/wp-cache-config.php to clear the cache at the end of pageload instead of by wp-cron. It will slow down page generation for a tiny number of your users though.
• The Last and Next garbage collection times are now in the timezone selected for your blog.
• Added an admin notice on the plugin page to warn that caching has to be enabled. A warning is shown below the plugin activation row too.
• If your site runs on a Windows server, I fixed a small problem with slashes and creating the config file.
• The plugin created empty supercache folders, but that’s fixed now.
• Bad Behaviour support seems to work nicely now!
• You can now relocate the supercache plugins folder. See $wp_cache_plugins_dir in wp-cache-config-sample.php.
• I added 2 new filters: wp_cache_served_cache_file in wp-cache-phase1.php (BB uses this) and wp_cache_file_contents in wp-cache-phase2.php where you can filter the contents of the newly created cache before it’s written out to a file.
• The readme.txt has been updated too warning about using NFS to store the cache folder, solving wp-cron problems, added the list of Apache modules required for expired pages to really expire in the browser cache.

I also added a donation link in the readme.txt and on the admin page. You can hide it with the click of a button but if you’re feeling generous, I’d appreciate a donation.
I don’t expect many donations, that’s how these things work, but if you tell me your site does 100,000 page views a day and you couldn’t live without caching I might be slightly annoyed if you come looking for free support.

PS. Looks like Bad Behavior support is broken because the docs on the BB site were a little misleading and I don’t use the plugin. Grab badbehaviour.php and copy into plugins/wp-super-cache/plugins/ overwriting the file of the same name in that folder.