Optimize a Large High Traffic Wordpress Blog
In this post, we shall go through the steps required to optimize a Wordpress blog. If you are a current customer of UNIXy, do know that we are happy to implement these changes for your blog free of charge. We are a fully managed provider so do take advantage of it.
There are times when hardware upgrades are not feasible due to either budgetary limits or time constraints. We understand that a Wordpress blog could be hosted on a shared platform or dedicated server (VPS included) so we have written this post with that in mind. The first 5 steps can be completed in a shared environment where access to global configuration files is not permitted by the provider. All 10 steps can be completed on a dedicated server or Virtual Private Server (VPS).
- WP Supercache
WP Supercache is a Wordpress plugin that once installed alleviates some of the burdens on the server. Essentially, it takes every visited PHP page, generates the HTML content, and stores it on disk for subsequent visits. This is called PHP caching. The performance gain is noticeable. Not only does it speed up requests and improves responsiveness but it also leads to less resource utilization on the server. To install WP Supercache, follow this link:
http://ocaoimh.ie/wp-super-cache/
2. Turn Autosave Off
The WP global variable AUTOSAVE_INTERVAL controls the how often Wordpress auto saves posts as they are edited. For example, while editing or writing a new posts, WP could be automatically saving tens of copies of your posts to the main Wordpress table. Each time such automatic save process kicks off the main posts table is locked in order to be updated, which prevents visitors from briefly accessing your blog. It also causes the load average to spike up. One could either increase the autosave interval or completely disable the functionality. To increase the interval to X number of seconds (the higher the better), do it as such inside the wp-config.php file:
define('AUTOSAVE_INTERVAL', 2200); // 2200 second autosave interval
To disable the autosave feature completely, create a simple plugin file and enable via wp-admin:
<?php
/*
Plugin Name: Disable Autosave
*/
function disable_autosave() {
wp_deregister_script('autosave');
}
add_action( 'wp_print_scripts', 'disable_autosave' );
?>
3. Disable Revisioning
This feature saves several revisions of the same post into the database. It clutters the posts table and ends up bloating indexes unecessarily. It’s best to disable this feature altogether if you don’t need it. Add this line to your wp-config.php to disable this feature:
define('WP_POST_REVISIONS', false);
No further action is needed.
4. Disable Non-Cacheable SQL Plugins
While it is a good idea to disable as many unneeded plugins as possible, it’s not always practical to do. But this step requires that you go through the code of each plugin and locate SQL queries that use the MySQL RAND() function. Because MySQL does not cache queries that use the random number generator function RAND(), there is a performance penalty associated with such plugins. For example, Random Post plugin uses RAND() in its select SQL, which forces the SQL to run against the database time and time again. You can locate the PHP scripts that use the RAND() function inside your plugin folder using this command:
grep -i "rand()" -r wp-content/plugins
Once located, one could either disable such plugin or replace MySQL RAND() with a PHP rand function. This way the PHP random function will be cached. The randomization will, however, not work as intended. The good news is that perceived functionality will not be much impacted.
5. Convert MyISAM Tables to InnoDB
The InnoDB engine is superior. There is no reason to run MyISAM anymore. Here is a Bash script that will convert all tables, that can be converted, to InnoDB. If you do not have access to a script shell, you can accomplish the same using phpMyAdmin or other MySQL management tools. Be sure to take a backup of the Wordpress database before running this script. Also, be sure to define a maintenance window for this change as the alter locks up tables temporarily making the blog inaccessible:
#!/bin/bash
DBNAME="database";
DBUSER="user";
DBPASS="pass";
for t in $(mysql -u$DBUSER -p$DBPASS --batch --column-names=false -e "show tables" $DBNAME);
do
echo "Converting table $t";
mysql -u$DBUSER -p$DBPASS -e "alter table ${t} type=InnoDB" $DBNAME;
echo "Repair table $t";
mysql -u$DBUSER -p$DBPASS -e "repair table ${t}" $DBNAME;
done
Remember that those who are hosting their Wordpress blog on a shared provider's server will not be able to proceed with the rest of the instructions. The following instructions require root-level access to the server and a technical understanding of systems.
6. Increase Query Cache
We have already covered MySQL's query cache thoroughly in a previous post. We will not cover this information here. Feel free to read our past post on our blog here:
http://blog.unixy.net/2009/06/improve-performance-with-mysql-query-caching/
7. Increase Sort Buffer Size
The MySQL sort_buffer_size variable controls the amount of memory that MySQL can allocate to dedicated to sorting. In other words, the more SQL queries that need to sort data the larger this value needs to be. But it shouldn't be that large as it can affect performance negatively. For example, you wouldn't fill up a large container of water only to find out you can't carry it for a mile. Instead, it's best to fill the container with only enough water. The same idea applies to sort_buffer_size. It is usually best to set it to slightly than the amount of L2 CPU cache. So for a Xeon x3430 with 8MB cache that would be around 6MB. The final my.cnf entry would then be:
sort_buffer_size = 6M
8. Increase Key Buffer Size
This configuration settings controls the amount of memory that MySQL can use to fit index blocks into memory while manipulating indexes. Increasing this value as much as possible (within reason) can improve performance greatly. It prevents MySQL from having to use the disk as temporary storage for its work area. Edit the main my.cnf file and put the following entry.
key_buffer_size = 128M
Restart MySQL for changes to apply.
9. Install and Configure Eaccelerator
Eaccelerator is a PHP cache module that ensures minimal CPU processing. It essentially renders PHP scripts once and saves the HTML output for subsequent calls. The benefits are important. Checkout the Eaccelerator Wiki on how to compile, configure, and run it here:
http://eaccelerator.net/wiki/InstallFromSource
10. Install Apache MPM Worker
Apache's Worker can have advantages over its default MPM Prefork. It is somewhat lightweight in the sense that it's threading based and can thus smoothout load average spikes when traffic increases. Worker requires a rebuild of Apache. Luckily, someone has already covered the steps requires to rebuild Apache with this MPM. Check it out here:
http://www.faqs.org/docs/Linux-HOWTO/Apache-Compile-HOWTO.html
With this step we conclude our crash course / guide to optimizing and improving Wordpress. If you are a customer and would like to implement any of these recommendations, don't hesitate to ping us. I hope you enjoyed this post.
That's all folks!