Call Rake task from migration

 You can call the rake task in migration by writing following

Rake::Task[this_is_rake_task'].invoke

Is the string has numeric value?

for check the string has numeric value or not then you can do it by below
s = "123cs"

then call method as below
is_numeric?(s)

and the method is as below
 def is_numeric?(s)
    s.to_s.match(/\A[+-]?\d+?(\.\d+)?\Z/) == nil ? false : true
  end

Run your rails application with apache2 and mongrel_clusters

Run your rails application with apache2 and mongrel_clusters

Install Apache 2.2 and enable the needed modules (url rewriting, proxy, proxy_balancer e proxy_http)

sudo apt-get install apache2

# enable your modules in apache
sudo a2enmod rewrite
sudo a2enmod proxy
sudo a2enmod proxy_balancer
sudo a2enmod proxy_http
sudo a2enmod proxy_connect

# if you not enabled any of the modules then may be errors occured while you restart your apache after adding the below configration
# Error may be encoutered it yoou have not enabled module rewrite is "Invalid command 'RewriteEngine', perhaps misspelled or defined by a module not included in the server configuration"

Install Mongrel, create a mongrel user, create the mongrel cluster
sudo gem install daemons gem_plugin mongrel mongrel_cluster --include-dependencies

You can continue with the same linux user to mongrel if you want otherwise you can create new user by
sudo /usr/sbin/adduser mongrel
This line creates new user mongrel withg same mongrel group
Now need to create one mongrel_cluster.yml
sudo mongrel_rails cluster::configure -e production -p 3010 -N 2 -c /home/user/projects/myapp -a 127.0.0.1 --user mongrel --group mongrel

here -e = your working environment
     -p = your port for run application
     -N = Number of instances of the application. here 2 instances for my application and port is 3010. so this application will work on 3010 and 3011 port
 --user = need to provide your linuxuser
--group = need to provide your linuxgroup

this line will create /config/mongrel_cluster.yml file with following command
user: mongrel
cwd: /home/user/projects/myapp
log_file: log/mongrel.log
port: "3010"
environment: production
group: mongrel
address: 127.0.0.1
pid_file: tmp/pids/mongrel.pid
servers: 2

now make sure that tmp and log folder has permission to the user/group which you have user in mongrel_cluster if not assign permission by
sudo chown -R mongrel:mongrel /path/to/app/tmp

# Now start mongrel clusters
sudo mongrel_rails cluster::start

Hopefully clusters is worked perfactly and you can get it run on multiple port 3010 and 3011
http://127.0.0.1:3010
http://127.0.0.1:3011

Now need to set proxy balancer for this app
For this need to create one host for you app
Go to sudo nano /etc/hosts

127.0.0.1 localhost
127.0.0.1 myapp

Now need to configure Apache configuration file (sudo gedit /etc/apache2/sites-available/default).

NameVirtualHost *:80

#we need this as on Ubuntu/debian by default Proxy is not allowed
<Proxy *>
  Order allow,deny
  Allow from all
</Proxy>

#Proxy balancer section (create one for each ruby app cluster)
  <Proxy balancer://myapp_cluster>
    BalancerMember http://myapp:3010
    BalancerMember http://myapp:3011
  </Proxy>

#Virtual host section (create one for each ruby app you need to publish)
<VirtualHost *:80>
    ServerAdmin webmaster@localhost
        ServerName myapp  
        DocumentRoot /home/user/projects/myapp/public/
    <Directory />
        Options FollowSymLinks
        AllowOverride None
    </Directory>
    <Directory /home/debian/chirag/mycalltime/public/>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride All
        Order allow,deny
        allow from all
    </Directory>

    ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
    <Directory "/usr/lib/cgi-bin">
        AllowOverride None
        Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
        Order allow,deny
        Allow from all
    </Directory>

    ErrorLog /var/log/apache2/error.log

    # Possible values include: debug, info, notice, warn, error, crit,
    # alert, emerg.
    LogLevel warn

    CustomLog /var/log/apache2/access.log combined

    Alias /doc/ "/usr/share/doc/"
    <Directory "/usr/share/doc/">
        Options Indexes MultiViews FollowSymLinks
        AllowOverride None
        Order deny,allow
        Deny from all
        Allow from 127.0.0.0/255.0.0.0 ::1/128
    </Directory>

  #Rewrite stuff
  RewriteEngine On

  # 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://myapp_cluster%{REQUEST_URI} [P,QSA,L]

</VirtualHost>


After configure the default file need to restart apache
sudo /etc/init.d/apache2 restart

Cheers....
You get your app running on multiple instanses with proxy balancer
http://myapp