Category Archives: WordPress

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.

WP Super Cache version 0.9 is now available. WP Super Cache is a page caching plugin for WordPress that will significantly speed up your website.

Update – if your blog is installed in a sub directory instead of at the root of your server, the .htaccess file might be wrong. Download and install the development version which corrects this. You’ll have to edit the .htaccess file (anyone want to volunteer to write an auto-upgrader?) and remove the rules between the lines # BEGIN WPSuperCache and # END WPSuperCache. Delete those lines too and visit your admin page. The plugin should do it’s stuff and spit out correct mod_rewrite rules for you. The dev version also has a few other bug fixes so if you’re adventurous have fun upgrading!
There’s no need to touch wp-content/cache/.htaccess

Are we nearing version 1? Possibly. In this release a number of bugs have been fixed and the following new features added:

1. Mobile user agents are detected and a different cache page created for them. If you use a plugin that displays a different theme to these devices it will hopefully work now. The plugin changes to “half-on” mode because the detection is done by PHP. Thanks to Alex King‘s WordPress Mobile Edition plugin for the detection code.
2. The number of cache files will be more than halved on a normal site with plenty of anonymous visitors. This should be a huge win for WordPress MU sites and very busy blogs.
3. The last and next garbage collection times are displayed on the admin page now.
4. In previous versions the newly generated page was delivered uncompressed to the first visitor even if the browser supported compression. I’ve fixed this but I’m not 100% certain it will work for everyone so it’s disabled by default. Edit wp-content/wp-cache-config.php and add “$wp_cache_gzip_first = 1;” to enable this. It’s enabled here.
5. If expiry time is longer than 30 minutes, garbage collection will be done every 10 minutes, else it’ll be done 10 seconds after the expiry time.

Unfortunately wp-content/advanced-cache.php will have to be updated again and it’s not as simple as copying the file from the plugin directory. Full instructions are printed on the admin page and it should auto update in most cases.

PS. Test your upgraded blog on Is my blog working, a project by fellow Automattican Alex Shiels.
Here’s the page for this site. 102ms page generation time is rather fast!

WP Super Cache version 0.8.9 is now available. WP Super Cache is a page caching plugin for WordPress that will significantly speed up your website.

This version fixes a number of bugs and adds two new features, but in case you run into problems upgrading, make sure you delete wp-content/advanced-cache.php before copying plugins/wp-super-cache/advanced-cache.php over it. Go on, read that again. Delete that file. Jonathan Dingman didn’t and when he copied the file over the symlink he overwrote wp-super-cache/wp-cache-phase1.php. His site went belly up and he started screaming for my head!!! Err no, he appeared on #wordpress asking why it didn’t work. Thanks Jonathan for working through the problem with me. My fault for not making the instructions clearer!

If this happens to you, take a deep breath and unzip the plugin again in the plugins folder and delete wp-content/advanced-cache.php

Anyway, the new features are:

1. Cache rebuild. Serve a static cache file to anonymous users while that file is being generated.
2. Disable the large global lock that makes every access to the cache atomic.

Besides those, I got rid of the symlinked file in wp-content/, and the plugin now copies a file called “advanced-cache.php” from the plugin directory to simplify things. Especially on operating systems where symlink isn’t available. Yes, that’s Windows.

If your site is horrendously busy and you get a ton of comments every day and you’re too broke to buy a new server, then the cache rebuild feature will help you a lot. You should see the load on your server go way down if you enable this. Anonymous users who visit a page where a comment has just been left will be served a static cache file from the supercache instead of all the requests trying to generate a brand new page. The page served to them might be a few seconds out of date but that trade off is worth it.
Here’s the original thread that inspired the idea. Thanks Tigertech for writing the patch and for sharing the performance graphs. Check out the load on his server, before and after the rebuild function was switch on:

If you’ve had problems with deleting the cache on your blog it *might* be because of file locks. Some hosts just have problems with them. The file locking in the plugin is very coarse. When the plugin wants to do any sort of write operation it grabs a lock, does the writes (which could include clearing expired files, or creating wp-cache and supercache cache files), and then releases the lock.
Any other process running the plugin that tries that won’t get a lock: new cache files won’t be created, and cache files won’t be cleared.
It isn’t a huge problem that the lock is so coarse because the writes don’t take very long (the lock is enabled after the page is generated), but some very busy sites take quite a while to clear their cache files.
On the downside, disabling the file lock won’t stop multiple cached files being generated simultaneously (great), but it also won’t stop multiple “clear cache” attempts either (boo!)
From what I recall of looking at the other cache plugins for WordPress, most of them don’t have any file locking and seem to do just fine.

I almost forgot! There is also a new debug mode. Edit wp-content/wp-cache-config.php and look for “$wp_cache_debug” and follow the instructions. It will send you a few emails when things don’t go right and may help track down any problems.

As a final note, I would like to sincerely thank Robert Wolf who spruced up the admin page and gave it a nice lick of paint and Michael Torbert for helping me debug the plugin a while back.

WP Super Cache version 0.8.7 is now available. WP Super Cache is a page caching plugin for WordPress that will significantly speed up your website.

This release addresses some issues large or busy sites had with deleting expired cache files. Some sites generated so many cache files that there were two many files generated, even when those files were cleared out every hour. To fix that I limited the recursive function that deletes the files to 100 deletions at a time. That function is called until all the cache files are deleted (or strictly speaking, no files are deleted. That’s how the expired file cleanup works).
It’s also possible to set the garbage collection interval to 10 minutes now which will also help.