Previously I talked about configuring a production Ruby on Rails applications using a Mongrel cluster with an Apache front end / load balancer. Now though a new Apache module was released called mod_rails which obviates the need for a Mongrel cluster. Seems promising, both for simplicity of installation and performance.

As mentioned in my post, Configuring Apache to work with a Mongrel Cluster, you need an Apache installation with mod_rewrite and mod_proxy_balancer. Unfortunately on the Red Hat installation I was using the default installation is Apache 2.0 which does not have mod_proxy_balancer. When I tried to upgrade it using up2date I got some errors that seemed to indicate this install was not properly registered. I then tried using the Apache 2.2 install done by the tech guy but this install did not have the modules I needed.

Therefore it was time for me to do the install by myself. Fortunately it was not hard with the help of this article, Building Apache 2.2 plus the manual.

Here is what I did.

$ wget http://apache.mirror99.com/httpd/httpd-2.2.8.tar.gz
$ tar xvfz httpd-2.2.8.tar.gz
$ cd httpd-2.2.8
$ ./configure --enable-rewrite=shared --enable-proxy=shared \
    --enable-proxy_balancer=shared --enable-proxy_http=shared
$ make
$ sudo make install
$ sudo /usr/local/apache2/bin/apachectl start

Previously I wrote about Configuring Capistrano and Mongrel. Now we are going to configure Apache to work with the Mongrel cluster.

For this article I used the chapter Setting Up A Development Environment in Agile Web Development with Rails, version 2.0, plus this article.

• Time For A Grown-Up Server: Rails, Mongrel, Apache, Capistrano and You

Capistrano working together with Mongrel allows you to deploy and restart Mongrel clusters quite nicely.

Configure Apache proxy balancer

Apache has a mod_proxy_balancer module which must be enabled. Once this is done you can add the following to the end of conf/httpd.conf or if you are on Red Hat Linux you can put the proxy balancing section in /etc/httpd/conf.d/myapp.proxy_cluster.conf and the virtual host section in /etc/httpd/conf.d/myapp.conf.

<Proxy balancer://mongrel_cluster>
  BalancerMember http://127.0.0.1:8000
  BalancerMember http://127.0.0.1:8001
  BalancerMember http://127.0.0.1:8002
</Proxy>

<VirtualHost *:80>
  Include conf/myapp.common (or Include conf.d/myapp.common)
  ErrorLog logs/myapp_errors_log
  CustomLog logs/myapp_log combined
</VirtualHost>

Configure Apache Virtual Host

Next you configure the virtual host that represents the Ruby on Rails application in the custom file conf/myapp.common or if you are on Red Hat Linux in /etc/httpd/conf.d/myapp.common.

ServerName myapp.com
DocumentRoot /usr/local/rails/myapp/current/public

<Directory "/usr/local/rails/myapp/current/public">
  Options FollowSymLinks
  AllowOverride None
  Order allow,deny
  Allow from all
</Directory>

RewriteEngine On

# Uncomment for rewrite debugging
#RewriteLog logs/myapp_rewrite_log
#RewriteLogLevel 9 

# Check for maintenance file and redirect all requests
RewriteCond %{DOCUMENT_ROOT}/system/maintenance.html -f
RewriteCond %{SCRIPT_FILENAME} !maintenance.html
RewriteRule ^.*$ /system/maintenance.html [L]

# Rewrite index to check for static
RewriteRule ^/$ /index.html [QSA] 

# Rewrite to check for Rails cached page
RewriteRule ^([^.]+)$ $1.html [QSA]

# Redirect all non-static requests to cluster
RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
RewriteRule ^/(.*)$ balancer://mongrel_cluster%{REQUEST_URI} [P,QSA,L]

Restart Apache

$ sudo /usr/local/apache2/bin/httpd -k restart

or

$ sudo /etc/init.d/httpd restart