It can be very helpful when debugging problems if you can print out information at a certain point in the manifest. This is a good way to tell, for example, if a variable isn't defined or has an unexpected value. Sometimes it's useful just to know that a particular piece of code has been run. Puppet's notify resource lets you print out such messages.
Define a notify resource in your manifest at the point you want to investigate:
notify { 'Got this far!': }
In addition to simple messages, we can output variables within our notify statements. Additionally, we can treat the notify calls the same as other resources, having them require or be required by other resources.