How to set up a Handler for a Notification or Subscription in a Defined Type

puppet

How do I add handler to a defined type in puppet? For example, if I have:

define foo::bar ($baz) {
 ...
}

How can I have handler in foo::bar to handle something that contains

...
   notify => Foo::Bar['zippidy']
...

?

The handler would then run various Execs inside conditional logic when it receives a notification.

Best Answer

You can notify a defined resource that you've declared elsewhere in the catalog. How about an example?

CentOS system, httpd installed and stopped. Tested with Puppet 2.7.18

$ service httpd status
httpd is stopped

Here's an example manifest that contains an exec resource inside a defined resource type, a declaration of that defined resource type and a service resource that notifies that defined resource type.

./notify_defined_types.pp

define foo(){

   exec { "${name}_exec":
     command     => "echo hello ${name}",
     path        => '/bin:/usr/bin',
     refreshonly => true,
     logoutput   => true,
   }

}

foo { 'bar': }

service { 'httpd':  
  ensure => running,  
  notify => Foo['bar'],  
}

When I apply this, the change of state in my httpd service resource triggers a notification to the Foo['bar'] resource. This notification will apply to any service or exec resources used inside the foo defined resource type. 

$ puppet apply notify_defined_types.pp 
notice: /Stage[main]//Service[httpd]/ensure: ensure changed 'stopped' to 'running'
notice: /Stage[main]//Foo[bar]/Exec[bar_exec]/returns: hello bar
notice: /Stage[main]//Foo[bar]/Exec[bar_exec]: Triggered 'refresh' from 1 events
notice: Finished catalog run in 0.51 seconds

$ puppet apply notify_defined_types.pp 
notice: Finished catalog run in 0.38 seconds

Make sense? You just simply notify the resource that you declared. It'll trigger any exec or service resources exposed inside the defined resource type.

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