What is Amazon RDS?

Amazon Relational Database Service (Amazon RDS) is a web service that makes it easy to set up, operate, and scale a relational database in the cloud. That means that you can have your MySQL database operate on Amazon’s cloud computers located all over the world. Just like they say:

Amazon RDS gives you access to the full capabilities of a familiar MySQL database. This means the code, applications, and tools you already use today with your existing MySQL databases work seamlessly with Amazon RDS. Amazon RDS automatically patches the database software and backs up your database, storing the backups for a user-defined retention period. You also benefit from the flexibility of being able to scale the compute resources or storage capacity associated with your relational database instance via a single API call.

According to Amazon there is no need to make any changes to your application in order to use Amazon RDS. Well, at least for WordPress and WordPress-MU they are right.

A standard WordPress installation, using Amazon RDS, is located at WordPressRDS.com and a WordPress-MU (the kind of WordPress that wordpress.com uses) is located at mu.WordPressRDS.com. I will keep this installation alive for a few days and then take it down since the use of Amazon RDS is not free.

If you would like to help me finance this demo please consider a donation via PayPal.

Amazon RDS is charged by the hour + storage + I/O requests and in and out data transfer (see full pricing). The smallest database instance you can get is with 1.7GB RAM with the cost of 0.11$ per hour. If you run a full month it sums up to about 82$/month. The next level is a huge jump to a large instance of 7.5GB RAM with the cost of 0.44$ per hour (~330$/month). However, for those who are seeking a multi-db solution for WordPress MU may consider testing two or three small instances.

So lets get started!

The first thing you will have to do is setup an Amazon RDS instance. If you don’t have an account with Amazon you should creat an AWS account. Once you have an account you may signup for Amazon RDS.

To set up the RDS instance read some of the resources available. If you use WordPress you probably would start with the PHP sample code. I may give specific code samples at a later time but you will have to use the following APIs (in this order):

1. CreateDBSecurityGroup – setup a database security group.
2. AuthorizeDBSecurityGroupIngress – authorize access from your servers IP for the above group.
3. CreateDBInstance – set up the instance and first database (including root user, password and database name).

If all goes well you may check the instance using the DescribeDBInstances API call and look for the ‘Status‘ field making sure it is in ‘Available‘ state. In the results of this call you will also see the unique host name of the database. Amazon calls it ‘endpoint address‘. If you got it your are done!

Now setup WordPress (or WordPress Mu)

The final step is to run a regular setup of WordPress (or WordPress MU). You are probably familiar with the setup screen (click on the image to enlarge):

See the ‘DataBase Host‘ field? That is where the ‘endpoint address‘ goes. I guess this is one of those other 1% cases. Now just continue the installation as usual.

A WordPress MU installation is just the same:

I have installed WordPress and WordPress-MU on Amazon RDS at WordPressRDS.com. Check it out and please consider a donation via PayPal to keep these installation running.

WP Super Cache is a static caching plugin for WordPress. It generates html files that are served directly by Apache without processing comparatively heavy PHP scripts. By using this plugin you will speed up your WordPress blog significantly.

Instructions on how to install the plugin can be found in the readme file that comes with the plugin. As noted in the file, installing the plugin for WordPress-Mu differs just a bit from the regular WordPress install:

If you are using WordPress MU you will need to install this in ‘wp-content/mu-plugins/wp-super-cache/’ and the file wp-cache.php must be copied into the mu-plugins directory.

But there is a small problem with the plugin that I find very annoying. Although the cache is cleared with every post update and every theme change, when a user updates his blog’s widget settings the cache is not cleared and the user will not have a clue what is going on. This will result in a flood of support tickets.

I have been trying to solve this issue without changing any core files but came short. Finally I edited the wp-admin/widgets.php file and added just after line 266 the following code:

// Added to clear WP-Super Cache after the widgets are updated.
// Code by Elad Salomons http://www.ringofblogs.com
if(function_exists('wp_cache_no_postid')) {
wp_cache_no_postid(0);
}

If someone finds a way to use a plugin for this please let me know. By the way, this should work just the same for the regular WordPress.

In a new forum thread this week a WordPress MU user asked an old question: how to set the default timezone offset for new blogs? The solution proposed was to edit the wp-admin/includes/schema.php file (line 275). This of course should work but it involves in changing wpmu core files, an option I think is not the best one.

The option I propose is to set the default timezone offset option, and other options as well, using a plugin. This is really simple by using the wpmu_new_blog hook. The entire thing is less than 10 lines of code:

<?php
function new_blogs_setting( $blog_id )  {
//set your options here:
update_option('gmt_offset', 2);
// stop editing here
return;
}
add_action('wpmu_new_blog', 'new_blogs_setting');
?>

The plugin can be downloaded from here (wpmu_new_blog.zip) and needs to be droped in the mu-plugins directory. One can add any other default option settings. In the case were a change of an option for existing blogs is required, the script to set global options for all WPMU blogs may be used.

You are probably familiar with the default favicon that comes with WordPress-MU – . This plugin allows each user to set his own favicon via the Options page.

This plugin by zappoman allows you to set an absolute or relative path to a common themes directory.