11.6. Scaling an Application Manually

Scalable applications can be manually scaled for various reasons that include:
  • If a certain load is anticipated on an application and it must be scaled accordingly.
  • There are a fixed set of resources for an application.
  • The cost must be controlled manually.

Procedure 11.1. To Scale an Application Manually:

  1. View the cartridges associated with a scalable application with the following command:
    $ rhc app show App_Name

    Example 11.7. Showing a Cartridge's Information

    $ rhc app show hybrid
    hybrid @ http://hybrid-automobile.example.com/ (uuid: fjoe04cabdc4efa8f2513a21e2ed27d)
    -----------------------------------------------------------------------------
      Domain:  	automobile
      Created: 	11:48 AM
      Gears:   	1 (defaults to small)
      Git URL: 	ssh://fjoe04cabdc4efa8f2513a21e2ed27d@hybrid-automobile.example.com/~/git/hybrid.git/
      SSH:     	fjoe04cabdc4efa8f2513a21e2ed27d@hybrid-automobile.example.com
      Deployment:	auto (on git push)
    
      php-5.4 (PHP 5.4)
      -----------------
        Scaling: x1 (minimum: 1, maximum: available) on small gears
    
      haproxy-1.4 (OpenShift Web Balancer)
      ------------------------------------
        Gears: Located with php-5.4
    
    Locate the scaling cartridges as required. The example shows that the php-5.4 cartridge is scaling.
  2. Set the minimum and maximum amount of gears the cartridge can use for scaling with the following command, specifying the application name and minimum and maximum number of gears:
    $ rhc cartridge scale Cart_Name -a App_Name --min Min_Gears --max Max_Gears

    Example 11.8. Setting the Maximum and Minimum Amount of Gears for a Cartridge

    $ rhc cartridge scale php -a hybrid --min 1 --max 10
    Setting scale range for php ... done
    
    php-5.4 (PHP 5.4)
    -----------------
      Scaling: x1 (minimum: 1, maximum: 10) on small gears
    
Set the minimum and maximum gears back to 1 to stop a cartridge from scaling.