WordPress Caching

As my blog’s traffic grows, I was recently advised by tech support that adding caching to my WordPress blog will help my web server. I understand that caching helps minimize server load, but are there any drawbacks to doing so?

James Bruce
2011-06-06 10:40:00

The latest w3tc fixes a lot, however I’ve had issues with various particular page widgets in the past, such as voting and other things. Try it out and see what you come up with!

Mike

2011-05-27 22:33:00

I’m not aware of any serious drawbacks to employing a WordPress caching plugin right now (at least not for W3 Total Cache). One problem could be that the static HTML pages [which are generated] aren’t always up to date, but I suppose that relies a lot on the settings and typically resolves itself within a few minutes.

Cache Doesn’t Clear

This is almost certainly the most common WordPress caching issue you’ll come into, if you haven’t already. You write new posts and use your plugin’s custom “Clear Cache” buttons, but nothing happens? These are, in most circumstances, the reasons:

Your www-data account does not have sufficient permissions to make changes to files.
The permissions on your cache folder prevent you from manipulating files.
A cached version of the site is still being served by your browser (clear browser cache).

The first two are essentially the same. In the first case scenario, make sure your www-data account, which runs the Apache/nginx installation on your server, has enough permissions to edit/modify files. If you don’t have a private server, you’ll have to contact your hosting provider to have this checked for you). If it doesn’t, you’ll need to change it.

sudo chown -R www-data:www-data /var/www
sudo chmod -R 770 /var/www

You can run the preceding code on your website’s server, which will give the user www-data read and write permissions to your home directory. In the vast majority of cases, this resolves the issue permanently, and you should be able to clear cache without difficulty. The second most common scenario is that the web user has permission to work in the home directory. But the cache folder shuts out, necessitating permission changes.

To begin, you must first determine the location of your cache folder, which will be different for each plugin. After you’ve done that, use the following command to alter the permissions:

chmod 755 /var/www/cache

If you’re still having issues at this point, you should contact your host directly to find out what’s going on. When it comes to caching plugins, this is one of the most common challenges that WordPress webmasters face.

It’s worth noting that a WordPress plugin may not be the greatest caching solution available; there are two more widely used approaches for caching your WordPress website that can prove to be far more effective at caching and give a more smooth experience for your readers. For both of them, here’s a little introduction.

Varnish Cashing Server

Varnish necessitates a basic understanding of Linux and the usual installation process on this platform.

It is a caching server that receives and answers to requests on behalf of the web server. Varnish interacts with the web server and vice versa. The real magic happens when the Varnish server starts storing responses in the server’s memory for repeat requests, effectively acting as a direct cache. Varnish can then immediately check each request to determine if it has previously been processed and send it out much faster, putting less burden on the actual backend server.

Varnish does require a server with some memory (ram), but other than that, getting it up and running isn’t difficult. It may be more enticing to larger sites than relying on a PHP script to do all the caching for you.

Alternative PHP Cache (APC)

Alternative PHP Cache is a free, open source (PHP license) framework that caches PHP bytecode compiler output in shared memory, minimizing parsing and disk I/O cost for later requests; and a shared memory cache for user data. As a result, for an application with a big source code base like Drupal, a 3x boost in page generation time is achievable.

APC may be installed on an Ubuntu server with just a few instructions. It offers a PHP script that can launch from the browser, as well as a straight command clean from the shell console.