Category Archives: Server Administration

Blazing fast WordPress with Nginx and Memcached

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Inspired by Eric Mann’s post on caching WordPress with Redis, I thought I’d experiment with a similar setup using Memcached. Any 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.

Benchmarks

To find out which of the two setups was faster, I measured the following metrics using WebPagetest and Blitz:

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Increasing the size of the LISH console

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If you’ve used Linode’s LISH console to get remote access to your server, you’re probably familiar with the way the console wraps everything to 60×20 (columns x rows) – even when you’re connected via ssh in a much larger terminal.

LISH Wrapping

Everything looks fine until…

LISH Wrapping

… The terminal wraps on itself

Luckily, the fix is easy. The LISH console is essentially emulating a raw serial port connected to the server. The serial port itself has no natural size, so the terminal gives it a default safe size (60×20). We can tell the terminal to change this size, using the stty command:

stty cols 200 rows 75

It’s as simple as that. Just set the cols and rows values to whatever size suits you.

If you’re having to do this a lot, you might consider putting this into your ~/.bashrc so that it runs each time you open a connection.

Solving “502 Bad Gateway” with nginx & php-fpm

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After upgrading php-fpm, my PHP-based sites were returning “502 Bad Gateway” errors. Here’s how I managed to solve it.

Check to make sure that php-fpm is running with ps auxww | 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 following line from:

listen = /var/run/php5-fpm.sock

To:

listen = 127.0.0.1:9000

Restart php-fpm with sudo /etc/init.d/php-fpm restart and everything should work normally again.

Automatic MySQL Backups

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It’s really easy to set up automatic MySQL backups using mysqldump. First, you need to set up a user with SELECT and LOCK TABLES privileges. In this example the user doesn’t have a password.

CREATE USER 'autobackup'@'localhost';
GRANT SELECT, LOCK TABLES ON *.* TO 'autobackup'@'localhost';

Next create the cron job with crontab -e. This job is set to run every day at 5:20am.

20 5 * * * mysqldump --user=autobackup dbname | gzip -c > /var/backups/dbname-`/bin/date +\%Y\%m\%d`.sql.gz

Don’t forget to change dbname to the name of the database that you want to backup. And that’s it – you’re done! This cron job will create a backup of your database and save it to /var/backups with a filename based on the current date, e.g. /var/backups/dbname-20120503.sql.gz

Recursively chmod Directories Only

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The find utility’s -exec flag makes it very easy to recursively perform operations on specific files or directories.

find . -type d -exec chmod 755 {} \;

This command finds all directories (starting at ‘dot’ – the current directory) and sets their permissions to 755 (rwxr-xr-x).

find . -type f -exec chmod 644 {} \;

Similarly, this command finds all files and sets their permissions to 644 (rw-r–r–).

 

Thanks to moveabletripe for the info.

Dynamic Virtual Hosts Using .htaccess

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There are several ways to set up virtual hosts on your web server. One of the more common methods is to manually create a <VirtualHost> record for each virtual host. While using this method is fine, it can end you up with a huge configuration file that is difficult to manage.

Because all of my virtual hosts are sub-directories of my web server’s base directory, I prefer to dynamically allocate the virtual host directory based on the host name. For example, I want wildlyinaccurate.localhost to point to /var/www/wildlyinaccurate. This can be achieved by modifying the .htaccess file of your web server’s base directory: Continue reading →