anchor.diff:  
   The broadcast mechanism is based on a simple mechanism where each node polls periodically a database table shwoing the command to execute. When the system (each node) picks up a new entry, it then sends a special bus event, so that different Kill Bill components and plugins can react to the event and carry out the action.
   
  -=== Installation/Uninstallation 
  +=== Installation/Uninstallation
   
   Installing/uninstalling a plugin using the API is slightly different than installing/uninstalling the plugin using KPM directly. The main reason has to do with the `pluginKey`:
   
  
positive.code: 
  * An entry in the official Kill Bill https://github.com/killbill/killbill-cloud/blob/master/kpm/lib/kpm/plugins_directory.yml[plugin repository],
  * A user provided key that will be used to identify this plugin when using the APIs. The user provided key must be unique and must contain a namespace (e.g MY_NAMESPACE:myKey). During the installation phase, and when using a user provided key, one must also specify additonal properties to specify the location of that plugin.
    
  The following APIs are supported:
  
  * INSTALL_PLUGIN: Install a plugin. The following properties are supported:
  
negative.code: 
  === KPM Plugin
  
  Plugin installation and uninstallation is handled by the KPM plugin, whose role is to simply listen for bus events to then delegate the installation/uninstallation to the KPM gem and then notify Kill Bill about the result.
  
  For all other operations (start/stop/restart), the KPM plugin is not involved.
  