Solving Wordpress error wp_cache_mutex.lock

If you came here a few hours ago, you probably were not able to access the blog and instead were greeted by a Wordpress error on the front page. Here’s how I solved this wp_cache_mutex problem.

Fortunately for me, the Wordpress plugin at fault was identified in the error.

Warning: fopen(/public_html/wp-content/cache/wp_cache_mutex.lock) [function.fopen]: failed to open stream: No such file or directory in /public_html/wp-content/plugins/wp-cache/wp-cache-phase2.php on line 96

The culprit: the WP-Cache plugin. WP-Cache makes a blog faster and more responsive by caching Wordpress pages and storing them in a static file that is served directly in future requests rather than loading and compiling the whole PHP code and building the page from the database. For some reason, though, the plugin acted up today and caused the error in the blog.

I thought simply disabling it in Administration Panel > Plugins would solve it but it never did. I deactivated the plugin but all I got afterwards was a blank, white screen and no matter how many times I refreshed the blog’s index page, the error was still there.

I then tried to disable all of the plugins thinking WP-Cache might be in conflict with another installed plugin, but after clicking Deactivate All Plugins, the blog error still did not disappear.

Probably I can solve it by going to the plugin settings, I thought. So I activated the WP-Cache plugin again and went directly to the WP-Cache plugin manager under Administration Panel > Settings.

There I clicked both the Delete expired and Delete cache options and, voila! the errors are now gone.

Yup, it is that simple but it took me more than an hour to figure that out. Anyway, I’ve temporarily disabled the WP-Cache plugin and will probably activate it again once the plugin author has determined why the plugin is causing that Wordpress error.

Hope this tip helped those who are having this error right now.