Straylight Run

At work, we had set up some wildcard virtual hosts in Apache config, and that got us by for quite some time.  But the time came when we needed finer-grained control of where to send incoming requests for different domains.  I needed to store my virtual hosts in a Mysql database, mapping domains to project directories.

I’ll spare you the problems I ran into and overcame, and just list the steps to get this done.  These instructions are based on a 64-bit, RHEL 5 server running the pre-packaged Apache server.  So if you follow these instructions on a different setup, of course, filenames, directories, versions, etc. may differ.

Install mod_vhost_dbd

Download dbd-modules from Google Code.  This is a great piece of code in the form of an Apache module that uses mod_dbd and a DBD Mysql (or other database) driver to fetch the DocumentRoot for a given domain from a database.

% wget http://dbd-modules.googlecode.com/files/dbd-modules-1.0.5.zip

Unzip the archive in a directory. As indicated on the website, build and install the module.

% apxs -c mod_vhost_dbd.c
% apxs -i mod_vhost_dbd.la

This places mod_vhost_dbd.so in /usr/lib64/httpd/modules.  Enable both this module and mod_dbd by adding two lines to httpd.conf, or equivalently creating a new include file in /etc/httpd/conf.d containing these lines.

LoadModule dbd_module modules/mod_dbd.so
LoadModule vhost_dbd_module modules/mod_vhost_dbd.so

In true unit fashion, now might be a good time to restart Apache, just so you can be sure everything is working up to this point.

% service httpd restart

Install Mysql DBD Driver to APR

Unfortunately, on my system, the Mysql DBD driver was nowhere to be found.  I had to rebuild Apache Portable Runtime (APR) utils with the Mysql driver enabled.

Download apr and apr-util from Apache.  Note these are not the latest versions, but the versions that matched the packages in worked for RHEL 5.

% wget http://archive.apache.org/dist/apr-1.2.8.tar.bz2
% wget http://archive.apache.org/dist/apr-util-1.2.8.tar.bz2

Unpack and untar these archives in the same parent directory.

Build and install APR.  Now, I do not think this is absolutely necessary, but it seems like a good idea to keep the versions in sync.

% ./configure --prefix=/usr
% make
% make install

Build and install apr-util.  Due to licensing issues, apr-util does not actually contain the Mysql DBD driver until apr-util-1.2.12.  Prior to that version, it must be downloaded separately, and the configure script rebuilt.

% wget http://apache.webthing.com/svn/apache/apr/apr_dbd_mysql.c
% ./buildconf --with-apr=../apr-1.2.7

Now for the three commands every Linux admin loves.

% ./configure --prefix=/usr --with-apr=/usr --libdir=/usr/lib64 --with-expat=builtin --with-ldap-include=/usr/include --with-ldap-lib=/usr/lib64 --with-ldap=ldap --with-mysql
% make
% make install

The first time I tried this, Apache could not find any LDAP-related modules.  Adding those configure switches seemed to do the trick.  Restart Apache.

% service httpd restart

Apache should now be able to query a Mysql database to get the DocumentRoot for a domain.  My VirtualHost block looked something like this.

    ServerName *.example.com
    DocumentRoot "/path/to/default/document/root"

    DBDriver mysql
    DBDParams host=localhost,user=root,pass=secret,dbname=vhosts

    DBDocRoot "SELECT path FROM vhosts WHERE host = %s"  HOSTNAME

For more details and instructions on mod_vhost_dbd configuration directives, read the project wiki.

To test things on our RHEL 5 production servers, I fire up CentOS 5 in VMWare.  While we build PHP 5.2 manually in production, I try to avoid doing so just for testing. Unfortunately, CentOS 5 is packaged with PHP 5.1 by default which becomes a big difference between my testing and production environments.  Fortunately, there is a CentOS yum repository out there with PHP 5.2.  I thought I’d document this here for anyone else with the same problem.

The solution I found starts with this thread about upgrading PHP on the CentOS forums.  To summarize, run these commands:

% cd /etc/yum.repos.d
% wget http://dev.cnetos.org/centos/5/CentOS-Testing.repo

Then, edit the .repo file and set the "enabled" value to "1".

% yum list available php
Available Packages
php.i386                                 5.2.6-2.el5s2          c5-testing