Note:
- A quick, down and dirty solution. There are more verbose resources on how to setup Mongrel Cluster and Apache. But this is also specifically tailored for Ubuntu Feisty Fawn.
- After installing mongrel, when executing
./script/server, you will not useWebrickanymore, but insteadmongrelfor development. You can still useWebrickif you want, but there isn’t much of a difference.
Plan of Attack
- Install, configure, and test Mongrel Cluster
- Install and test Apache
- Start Mongrel Cluster on boot
Installing Mongrel Cluster
sudo apt-get install ruby1.8-dev sudo gem install -y mongrel mongrel_cluster
Note: If you see the following make sure you select the latest version of mongrel for ruby. In this case option 2.
Select which gem to install for your platform (i486-linux)
1. mongrel 1.0.1 (mswin32)
2. mongrel 1.0.1 (ruby)
3. mongrel 1.0 (mswin32)
4. mongrel 1.0 (ruby)
5. Skip this gem
6. Cancel installation
>
Configuring Mongrel Cluster
Go to your Rails application directory and execute:
mongrel_rails cluster::configure -p 8000 -n 3
This allows mongrel to spawn 3 instance to handle the load. Each instance will open on port 8000, and succeeding. So that is 8000, 8001, and 8002.
Note: The mongrel_rails command has alot of options. Executing mongrel_rails -h will get you more information. All of these options can be changed later.
This will create the a mongrel_cluster configuration file in RAILS_ROOT/config/mongrel_cluster.yml 
Testing Mongrel Cluster
In your Rails application directory, execute:
mongrel_rails cluster::start
Now open up http://localhost:8000/, http://localhost:8001/, and http://localhost:8002/ to ensure that your site is working perfectly fine.
Installing Apache
Enter into the Terminal:
sudo apt-get install apache2 sudo a2enmod proxy_balancer sudo a2enmod proxy_http sudo a2enmod rewrite
We will now create a common rails configuration file. As root open up /etc/apache2/mods-available/rails.conf , and insert the following:
ServerName railsapp.com
DocumentRoot /var/www/railsapp.com/public
<Directory "/var/www/railsapp.com/public">
Options FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
</Directory>
RewriteEngine On
# Uncomment for rewrite debugging
#RewriteLog logs/railsappapp_rewrite_log
#RewriteLogLevel 9
# Check for maintenance file and redirect all requests
# ( this is for use with Capistrano's disable_web task )
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]
# Deflate
AddOutputFilterByType DEFLATE text/html text/plain text/css
# ... text/xml application/xml application/xhtml+xml text/javascript
BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4.0[678] no-gzip
BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
# Uncomment for deflate debugging
#DeflateFilterNote Input input_info
#DeflateFilterNote Output output_info
#DeflateFilterNote Ratio ratio_info
#LogFormat '"%r" %{output_info}n/%{input_info}n (%{ratio_info}n%%)' deflate
#CustomLog logs/myapp_deflate_log deflate
Now we’ll set up the virtual host for our site railsapp.com For the last time as root open up /etc/apache2/sites-available/railsapp and insert the following:
Listen 8080
<VirtualHost *:8080>
<Location />
SetHandler balancer-manager
Deny from all
Allow from localhost
</Location>
</VirtualHost>
<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 /etc/apache2/mods-available/rails.conf
ErrorLog /var/log/apache2/rails_errors_log
CustomLog /var/log/apache2/rails combined
</VirtualHost>
The first VirtualHost enables a front end for load balancing, available only to localhost on port 7999.
The second VirtualHost is our rails application. Notice how it is pulling in our default configuration (/etc/apache2/mods-available/rails.conf ). If you want to make changes you can specify it here. Need to specify a ServerName directive? Put it in here.
Lets enable the virtual host
sudo a2ensite railsapp
and restart Apache.
sudo /etc/init.d/apache2 restart
Now pull up your the domain you entered and your Rails application should load!
Note: If you can’t seem to access your site, its because the default virtual host has a higher precedence. Execute sudo a2dissite default 
. Similarly ensure that you are access your site via the domain you specified in the ServerName directive. In this case railsapp.com
If everything is work, you are on your way to more production based hosting solution.
Start Mongrel Cluster on Boot
Create mongrel_cluster conf directory (/etc/mongrel_cluster).
sudo mkdir /etc/mongrel_cluster
In the Mongrel Cluster gem, there is an init.d script you need to copy.
sudo cp /usr/lib/ruby/gems/1.8/gems/mongrel_cluster-0.2.1/resources/mongrel_cluster/mongrel_cluster /etc/init.d
Now let’s make the script executable.
sudo chmod +x /etc/init.d/mongrel_cluster
Now we need to add th init.d script to startup.
On Ubuntu:
sudo update-rc.d mongrel_cluster defaults
On RHEL/CentOS:
/sbin/chkconfig --level 345 mongrel_cluster on
Now create a symbolic link from RAILS_ROOT/config/mongrel_cluster.yml to a file in /etc/mongrel_cluster:
sudo ln -s /path/to/railsapp/config/mongrel_cluster.yml /etc/mongrel_cluster/railsapp
There you have it, you should be good to go!
Comments, bugs, problems, improvements
Have any bug, or problem? Leave a comment please.
In case anyone else comes across this.. The command to create the cluster config file is missing the -c option which tells the cluster where the app is located.
should be something like this:
mongrel_rails cluster::configure -p 8000 -N 3 -c /var/www/my_rails_app
Otherwise, how is the mongrel_cluster script supposed to know where the app is? Maybe the options were different at the time this was written up?
I’m sorry, you seem to have mistaken me for someone who cares.
Ok i’ve got a noobish question (if anybody still visits this place)
What if I want to run multiple application with load-balancer. How can I make a seperate entry for a new application and make sure it gets a new load-balancer so it doesnt end up proxy-ing it to an other application.
A word of note: Ruby 1.8.5 doesnt work with mongrel_cluster 1.0.2
you need to install manually (not apt-get) the 1.8.6 version
I’m running into a problem with the Apache2 setup. Every time I try and access the site I receive a “404 Not Found” page. I’m guessing the rewrite rules are not in effect, but have no clue how to make them work properly.
Any help is much appreciated!
I figured it out: there is a typo in this command:
mongrel_rails cluster::configure -p 8000 -n 3
The -n option is case sensitive. Use -N to set the number of servers. -n sets number of threads.
When I start my cluster as you describe, I only get responses on ports 8000 and 8001, not 8002 for some reason.
Hi!
Thanks a lot for this very instructive tutorial ! it helps me to get my small application up !
The only problem is when I tried to lunch mongrel_cluster, where I have problem.
In fact the mongrel_rails start -e production is working fine. However mongrel_rails cluster::start is not working. The log I get the following output :
starting port 8000
starting port 8001
starting port 8002
But when I lunched the browser to the application url and port 8000 for
example, the mongrels seems not working.
I looked at the log file and get for the first mongrel instance :
** Daemonized, any open files are closed. Look at tmp/mongrel.8000.pid
and log/mongrel.8000.log for info.
** Starting Mongrel listening at 0.0.0.0:8000
** Changing group to mongrel.
** Changing user to mongrel.
** Starting Rails with production environment…
** Mounting Rails at /home/rails/projects/myapps…
/usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:30:in
`gem_original_require’: no such file to load –
/home/rails/projects/jokes/config/environment (LoadError)
from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:30:in
`require’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/rails.rb:157:in
`rails’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:116:in
`cloaker_’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:138:in
`call’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:138:in
`listener’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:98:in
`cloaker_’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:51:in
`call’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:51:in
`initialize’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:83:in `new’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:83:in `run’
from
/usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/command.rb:211:in
`run’
from /usr/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:248
from /usr/bin/mongrel_rails:16:in `load’
from /usr/bin/mongrel_rails:16
It’s the same thing for the two other instances.
My mongrel cluster configuration is as follows :
user: mongrel
group: mongrel
cwd: /home/rails/projects/myapps
log_file: log/mongrel.log
port: “8000″
environment: production
address: 127.0.0.1
pid_file: tmp/mongrel.pid
servers: 3
Do you have any idea of this problem ?
Thanks in advance !!
Addam
I did the “Start Mongrel Cluster on Boot” a bit different – see link
http://pieter-mantis.blogspot.com/2007/07/start-mongrel-cluster-on-boot-ubuntu.html
I did the “Start Mongrel Cluster on Boot” a bit different – see link
Very handy. Only extra item I needed was to make sure the link in /etc/mongrel_cluster finished in .yml
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Hey!
The proxy_http fixed the 403, thanks!
Regards,
LoCusF
Hi locuscf!
Thanks for noticing the error (wrt to the current/public) That’s off my capistrano setup, I must have forgotten to remove it. just make it webapp/public.
The other fault is that I forgot to include enable other apache module:
Hope this helps
Regards,
Aizat
Hi!
I have a problem with accessing a certain command (ie. http://localhost/controller/action), this gives me a 403 Forbidden. I have done everything like you have shown on this tutorial.
PS. How do I deploy my app since I don’t have wepapp/current/public ?
Regards,
LoCusF
Hi derek,
Yes I’ll admit that getting srails working is harder than getting php un and running
contact me privately regarding your rails problems, and maybe we can sort it
.
Regards,
Aizat
i spent a few hours trying to get it to work and failed
i have to say that is bad compared to a lamp install!
Thanks for the advice
Got a write-up on combination RoR + mongrel_cluster + apache and RoR + mongrel_cluster + pound. It seems the later combination is less resource hungry while the former is more flexible due to powerful rewrite module of apache httpd. Stripping down apache httpd helps by removing unused modules and lesser file descriptor writing.