细柳营

Indeed it’s very easy to get WPMU installed and up, but you’ll find the number of tables in WPMU database increases every time a new blog is created. If you’re providing public blogging service, the number of tables is going to 100, 1000, … very soon. Yes, WPMU is great, but the tables keep increasing, that may drive you mad. I was mad, at least.

In WPMU version 2.7, there are 9 global tables: blogs, blog_versions, registration_log, signups, site, sitecategories, sitemeta, usermeta, users. These 9 tables are fixed and serving for WPMU system globally. Every blog has its own 8 tables: comments, links, options, postmeta, posts, terms, term_relationships, term_taxonomy. These 8 tables are created over and over every new blog is created.

This designing is cool and useful from scalability view, especially for those big blogging service providers, wordpress.com is a good example. But WPMU uses only one database by default, it’s hard to manage the excessive tables in one database, and the performance should also not be good. OK, here comes HyperDB, which can solve this problem. Actually HyperDB is derived from the code using by wordpress.com.

Before starting installing and configuring, we need to define a rule for databases. In this post, the rule is:

• One database (wpmu_db0) for the global tables and the tables of first blog. It can be called global database.
• Additional 3 databases (wpmu_db1, wpmu_db2, wpmu_db3) for the tables of other blogs, each database serves 2 blogs.

Of course, you can define your own rules based-on your needs. It’s flexible.

We can start now. The first thing is to set up a standard WPMU using the global database in the installation wizard. After that, go to WordPress website and download HyperDB. The version I’m using is 2008-11-27. There are three files in HyperDB package:

• db.php, which needs to be uploaded to wp-content directory
• db-settings.php, which needs to be uploaded to the directory that holds wp-config.php
• readme.txt, oh, you know what it means

Then add the following lines near the top of wp-config.php

define('WPMU', true);
require('db-settings.php');

Then add the blow code at the bottom of db-settings.php

// a handy function for mapping blog tables to dataset
function add_blog_tables($ds, $blog_id){
  add_db_table($ds, 'wp_' . $blog_id . '_comments');
  add_db_table($ds, 'wp_' . $blog_id . '_links');
  add_db_table($ds, 'wp_' . $blog_id . '_options');
  add_db_table($ds, 'wp_' . $blog_id . '_postmeta');
  add_db_table($ds, 'wp_' . $blog_id . '_posts');
  add_db_table($ds, 'wp_' . $blog_id . '_terms');
  add_db_table($ds, 'wp_' . $blog_id . '_term_relationships');
  add_db_table($ds, 'wp_' . $blog_id . '_term_taxonomy');
}
 
// add databases
add_db_server('global', 0, 'mysql3326_1', 1, 1, 'localhost:3326', '', 'wpmu_db0', 'wpuser', 'thepwd');
add_db_server('s1', 0, 'mysql3326_2', 1, 1, 'localhost:3326', '', 'wpmu_db1', 'wpuser', 'thepwd');
add_db_server('s2', 0, 'mysql3306_1', 1, 1, 'localhost:3306', '', 'wpmu_db2', 'wpuser', 'thepwd');
add_db_server('s3', 0, 'mysql3306_2', 1, 1, 'localhost:3306', '', 'wpmu_db3', 'wpuser', 'thepwd');
 
// add global tables which are in global database
add_db_table('global',  'wp_blogs');
add_db_table('global', 'wp_blog_versions');
add_db_table('global', 'wp_registration_log');
add_db_table('global', 'wp_signups');
add_db_table('global', 'wp_site');
add_db_table('global', 'wp_sitecategories');
add_db_table('global', 'wp_sitemeta');
add_db_table('global', 'wp_usermeta');
 
// add the tables for the first blog (created during wpmu installation)
// the first blog's tables are in global database
// of course, you can move it to any database you want
add_blog_tables('global', 1);
 
$dbsnum=3; // 3 additional databases
$blogs_per_db=2; // each database serves 2 blogs
 
for($db_id=1; $db_id<=$dbsnum; $db_id++){
  $dataset = 's' . $db_id;
  $max = $db_id * $blogs_per_db + 1; // include
  $min = $max - $blogs_per_db + 1; // include
  for($blog_id=$min; $blog_id<=$max; $blog_id++){
    add_blog_tables($dataset, $blog_id);
  }
}

That’s it!

Resovling Domain Names Locally

Wanna try WPMU on local machine? If you use localhost or 127.0.0.1 as the server address directly, you always get a message similar to the following:

Do not use an IP address (like 127.0.0.1) as your server address. Do not use a single word hostname like localhost.

That means a FQDN is needed, the good thing is that it’s easy to resolve domain names virtually locally. Open the hosts file:

• C:\WINDOWS\system32\drivers\etc\hosts (Windows)
• /etc/hosts (Linux)

Add or modify something, and make sure there is a line like the following in the file:

127.0.0.1    localhost hys.lan bloga.hys.lan blogb.hys.lan blogc.hys.lan blogd.hys.lan

Here, hys.lan is used to install WPMU, blog(a-d).hys.lan are addresses for testing, I’ll use these four to create weblogs.

Configuring Apache

Make sure two things:

• Apache is listening on port 80, because WPMU doesn’t support server address with port number.
• mod_rewrite is enabled.

Then adds a virtual host section:

<VirtualHost *:80>
  DocumentRoot /opt/wordpress-mu
  ServerName hys.lan
  ServerAlias *.hys.lan
  <Directory "/opt/wordpress-mu">
    AllowOverride FileInfo
    Order allow,deny
    Allow from all
  </Directory>
</VirtualHost>

Preparing Database

Create an empty database, and grant permissions to a database user.

mysql> create database wpmu_db;
mysql> grant all privileges on wpmu_db.* to wpuser@'%' identified by 'thepwd';
mysql> flush privileges;

Installing WPMU

It’s very easy to get WPMU up. Open your browser, and type the server address, in my case, it’s http://hys.lan. Provide the required information, and press the “Submit” button to go. Waiting for a while, WPMU is installed and runs successfully.