Using EPP templates

EPP templates are a new feature in Puppet 3.5 and newer versions. EPP templates use a syntax similar to ERB templates but are not compiled through Ruby. Two new functions are defined to call EPP templates, epp, and inline_epp. These functions are the EPP equivalents of the ERB functions template and inline_template, respectively. The main difference with EPP templates is that variables are referenced using the Puppet notation, $variable instead of @variable.

How to do it...

1. Create an EPP template in ~/puppet/epp-test.epp with the following content:

   This is <%= $message %>.

2. Create an epp.pp manifest, which uses the epp and inline_epp functions:

   $message = "the message"
   file {'/tmp/epp-test':
     content => epp('/home/thomas/puppet/epp-test.epp')
   }
   notify {inline_epp('Also prints <%= $message %>'):}

3. Apply the manifest making sure to use the future parser (the future parser is required for the epp and inline_epp functions to be defined):

   t@mylaptop ~/puppet $ puppet apply epp.pp --parser=future
   Notice: Compiled catalog for mylaptop in environment production in 1.03 seconds
   Notice: /Stage[main]/Main/File[/tmp/epp-test]/ensure: defined content as '{md5}999ccc2507d79d50fae0775d69b63b8c'
   Notice: Also prints the message
   

4. Verify that the template worked as intended:

   t@mylaptop ~/puppet $ cat /tmp/epp-test 
   This is the message.
   

How it works...

Using the future parser, the epp and inline_epp functions are defined. The main difference between EPP templates and ERB templates is that variables are referenced in the same way they are within Puppet manifests.

There's more...

Both epp and inline_epp allow for variables to be overridden within the function call. A second parameter to the function call can be used to specify values for variables used within the scope of the function call. For example, we can override the value of $message with the following code:

file {'/tmp/epp-test':
  content => epp('/home/tuphill/puppet/epp-test.epp',
    { 'message' => "override $message"} )
}
notify {inline_epp('Also prints <%= $message %>',
  { 'message' => "inline override $message"}):}

Now when we run Puppet and verify the output we see that the value of $message has been overridden:

t@mylaptop ~/puppet $ puppet apply epp.pp --parser=future
Notice: Compiled catalog for mylaptop.pan.costco.com in environment production in 0.85 seconds
Notice: Also prints inline override the message
Notice: Finished catalog run in 0.05 seconds
t@mylaptop ~/puppet $ cat /tmp/epp-test 
This is override the message.