Inspired by Eric Mann’s post on caching WordPress with Redis, I thought I’d experiment with a similar setup using Memcached. Any in-memory caching system should work just as well, but I’ve chosen Memcached because it’s already running on my server and because PHP already has a built-in libmemcached API.
My current setup is Nginx and PHP-FPM, with WP Super Cache. The cache is saved to the filesystem, allowing Nginx to serve static files (which it is very good at) without needing to pass any requests to PHP. This setup has worked very well, so I’ll be using it as a baseline.
To use Memcached, every request needs to be passed to PHP. My gut feeling was that this would be slower than serving static files with Nginx due to the overhead of spinning up a PHP process for each request.
To find out which of the two setups was faster, I measured the following metrics using WebPagetest and Blitz : (Read more)
After upgrading php-fpm, my PHP-based sites were returning “502 Bad Gateway” errors. This can happen when the php5-fpm package reconfigures itself to listen on a different socket. Here’s how you can solve it.
Check to make sure that php-fpm is running with
ps aux | grep php - if you can’t see any php-fpm processes in the output, then you may need to re-install php-fpm. If php-fpm is running okay, then skip this first step.
sudo apt-get remove php5 php5-cgi php5-fpm
sudo apt-get install php5 php5-cgi php5-fpm
The thing to notice here is that the order in which you install the packages is important. In the past I have found that installing them in the wrong order causes the packages to be configured incorrectly.
Next, get php-fpm to listen on the correct host/port. In
/etc/php5/fpm/pool.d/www.conf change the
listen value to match the
fastcgi_pass location in your Nginx configuration. For example, I changed mine from:
listen = /var/run/php5-fpm.sock
If you are configuring php-fpm to listen on a Unix socket, you should also check that the socket file has the correct owner and permissions. While I wouldn’t recommend it, you can simply give read-write permissions to all with
sudo chmod go+rw /var/run/php5-fpm.sock.
Restart php-fpm with (Read more)
sudo service php5-fpm restart and everything should work normally again.