SUMMARY

Mongrel is a fast HTTP library and server for Ruby that is intended for hosting Ruby web applications using the Apache webserver.  Proxying requests to a mongrel cluster is just one way of serving your Ruby on Rails web applications.

STEPS

1. Update ruby to 1.8.6:

The (dv) 3.x servers come with ruby 1.8.5 installed.  It is recommended to upgrade to 1.8.6.  Installing yum is the best way to remove the older version.

First install yum by following this article.

Now that yum is installed we will remove ruby.  Please answer yes at the confirmation dialog:

yum remove ruby

Now we will download the source for ruby 1.8.6 from ruby's FTP site:

wget ftp://ftp.ruby-lang.org:21/pub/ruby/1.8/ruby-1.8.6.tar.gz

Decompress the file and change to the new directory:

tar xzvf ruby-1.8.6.tar.gz && cd ruby-1.8.6

Now we will compile the source and install the new binaries on your server at /usr/local/bin/:

./configure && make && make install

Refresh your profile and verify that you are now running ruby 1.8.6

source /etc/profile;ruby -v

If your upgrade was successful you should see the following output:

ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]

2. Install Rubygems:

Create a configuration file with the proper directive and refresh your environment:

echo 'export PATH=/usr/local/bin:$PATH' > /etc/profile.d/ruby.sh; source /etc/profile

Download the RubyGems distribution:

wget http://rubyforge.org/frs/download.php/45905/rubygems-1.3.1.tgz

Unpack the archive:

tar -xzvf rubygems-1.3.1.tgz

Change to the decompressed directory:

cd rubygems-1.3.1

Add the following environment variable and create your gems directory:

export GEM_HOME=/usr/local/rubygems/gems; mkdir -p $GEM_HOME

Execute the following ruby script to set up ruby with the above path:

ruby setup.rb all --prefix=/usr/local/rubygems

Create a /etc/profile.d/rubygems.sh file with vi:

vi /etc/profile.d/rubygems.sh

Copy the following contents into the file:

export GEM_HOME=/usr/local/rubygems/gems
export GEM_PATH=/usr/local/rubygems/gems
export RUBYLIB=/usr/local/rubygems/lib
export PATH=/usr/local/rubygems/gems/bin:/usr/local/rubygems/bin:$PATH

Refresh your environment profile once more:

source /etc/profile

3. Install Rails and related dependencies:

gem install rails
gem install daemons
gem install fastthread
gem install mongrel
gem install mongrel_cluster
gem install mysql -- --with-mysql-include=/usr/include/mysql --with-mysql-lib=/usr/lib/mysql

Bulk updating Gem source index for: http://gems.rubyforge.org
ERROR: While executing gem ... (Gem::GemNotFoundException)
Could not find 'X' (> 0) in any repository

4. Configure the mongrel_cluster daemon:

Create the 'mongrel' user:

adduser mongrel

Copy the init script for mongrel_cluster to the init.d directory and make it executable:

cp /usr/local/rubygems/gems/gems/mongrel_cluster-1.0.5/resources/mongrel_cluster /etc/init.d/; chmod +x /etc/init.d/mongrel_cluster

Configure the mongrel_cluster daemon to start automatically:

/sbin/chkconfig --level 345 mongrel_cluster on

Create some necessary directories that mongrel_cluster needs to exist:

mkdir /etc/mongrel_cluster
mkdir /var/run/mongrel_cluster

5. Set up your initial 'testapp' domain:

Create a new domain inside of your Plesk Control Panel. We will call it testapp.mt-example.com

Edit and/or create /var/www/vhosts/testapp.mt-example.com/conf/vhost.conf with vi:

vi /var/www/vhosts/testapp.mt-example.com/conf/vhost.conf

Insert all of the following lines into that file:

<Directory /var/www/vhosts/testapp.mt-example.com>
Options +FollowSymLinks
</Directory>
RewriteMap servers rnd:/var/www/vhosts/testapp.mt-example.com/rails/servers.txt
<Directory /var/www/vhosts/testapp.mt-example.com/httpdocs>
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ http://${servers:server}/$1 [P]
</Directory> 

/usr/local/psa/admin/sbin/websrvmng -a

Change to the domain's directory:

cd /var/www/vhosts/testapp.mt-example.com

Create the 'rails' directory and change ownership to your domain user.  Install a test application called testapp using the rails command:

mkdir rails; chown username:psaserv rails; cd rails
rails testapp

Now we must remove the default 'httpdocs' directory and create a symbolic link (symlink) from the testapp's public folder:

mv /var/www/vhosts/testapp.mt-example.com/httpdocs /var/www/vhosts/testapp.mt-example.com/httpdocs.old
ln -s /var/www/vhosts/testapp.mt-example.com/rails/testapp/public /var/www/vhosts/testapp.mt-example.com/httpdocs

Create a file called servers.txt in /var/www/vhosts/testapp.mt-example.com/rails/servers.txt with the following proxy information:

echo 'server 127.0.0.1:4000|127.0.0.1:4001|127.0.0.1:4002' > /var/www/vhosts/testapp.mt-example.com/rails/servers.txt

Generate the mongrel_cluster.yml file:

cd /var/www/vhosts/testapp.mt-example.com/rails/testapp
mongrel_rails cluster::configure -N 3 -p 4000 -e production -a 127.0.0.1 -c /var/www/vhosts/testapp.mt-example.com/rails/testapp --user mongrel --group mongrel

Modify the line in /var/www/vhosts/testapp.mt-example.com/rails/testapp/config/mongrel_cluster.yml to reflect the appropriate pid file directory:

perl -pi -e 's/tmp\/pids\/mongrel\.pid/\/var\/run\/mongrel_cluster\/mongrel\.pid/g' /var/www/vhosts/testapp.mt-example.com/rails/testapp/config/mongrel_cluster.yml

Symlink mongrel_cluster.yml to /etc/mongrel_cluster/testapp.yml:

ln -s /var/www/vhosts/testapp.mt-example.com/rails/testapp/config/mongrel_cluster.yml /etc/mongrel_cluster/testapp.yml

Test the apache configuration:

/etc/init.d/httpd configtest

If all is OK, reload the apache configuration:

/etc/init.d/httpd reload

Modify /var/www/vhosts/testapp.mt-example.com/rails/testapp/public/.htaccess to contain the proper directive:

cp /var/www/vhosts/testapp.mt-example.com/rails/testapp/public/.htaccess /var/www/vhosts/testapp.mt-example.com/rails/testapp/public/.htaccess.old && echo 'ErrorDocument 500 "Application error Rails application failed to start properly"' > /var/www/vhosts/testapp.mt-example.com/rails/testapp/public/.htaccess

ErrorDocument 500 "Application error Rails application failed to start properly"

Fix permissions for your application's 'sessions' and 'log' folders:

chown -R mongrel:mongrel /var/www/vhosts/testapp.mt-example.com/rails/testapp/tmp/sessions

Start the mongrel_cluster daemon:

 /etc/init.d/mongrel_cluster start

** Ruby version is not up-to-date;
loading cgi_multipart_eof_fixit is normal to proceed.

You can now view your application at: http://testapp.mt-example.com/

Congratulations!!

Revisions:

05-05-2009: Changed article to point to new yum article. Thanks to Jerson V.
01-30-2009: Fixed "tar xzvf ruby-1.8.6.tar.gz && cd ruby-1.8.6" Thanks for the comment Stephen K
12-24-2008: Updated with instructions for using rubygems 1.3.1.  Added steps for upgrading ruby to version 1.8.6.  Other clarifications to ease overall install.  Happy Holidays!!
09-03-2008: Updated article to reflect new RubyGems version.
05-14-2008: Fixed the categories this article was set to.
05-07-2008: : Made some slight corrections to code examples to verify proper syntax.
05-06-2008: : Fixed some issues from our import from the old KnowledgeBase. - Thanks to Mike Nicholaides for pointing this out.